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SHEFFIELD, C. L., T. L. CRIPPEN, K. ANDREWS, R. J. BONGAERTS e D. J. NISBET. "Planktonic and Biofilm Communities from 7-Day-Old Chicken Cecal Microflora Cultures: Characterization and Resistance to Salmonella Colonization†". Journal of Food Protection 72, n. 9 (1 settembre 2009): 1812–20. http://dx.doi.org/10.4315/0362-028x-72.9.1812.
Testo completoAbstract (sommario):
Information implicating bacterial biofilms as contributory factors in the development of environmental bacterial resistance has been increasing. There is a lack of information regarding the role of biofilms within the microbial ecology of the gastrointestinal tract of food animals. This work used a continuous-flow chemostat model derived from the ceca of 7-day-old chicks to characterize these communities and their ability to neutralize invasion by Salmonella enterica serovar Typhimurium. We characterized and compared the biofilm and planktonic communities within these microcosms using automated ribotyping and the Analytical Profile Index biotyping system. Eleven species from eight different genera were identified from six culture systems. Klebsiella pneumoniae was isolated from all planktonic communities and four of the biofilm communities. Three of the communities resisted colonization by Salmonella enterica serovar Typhimurium, two communities suppressed growth, and one community succumbed to colonization. In cultures that resisted colonization, no Salmonella could be isolated from the biofilm; in cultures that succumbed to colonization, Salmonella was consistently found within the biofilms. This study was one of a series that provided a molecular-based characterization of both the biofilm and planktonic communities from continuous-flow culture systems derived from the cecal microflora of chicks, ranging in age from day-of-hatch to 14 days old. The one common factor relating to successful colonization of the culture was the presence of Salmonella within the biofilm. The capacity to sequester the introduced Salmonella into the biofilm appears to be a contributing factor to the inability of these cultures to withstand colonization by the Salmonella.
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Schooling, S. R., U. K. Charaf, D. G. Allison e P. Gilbert. "A role for rhamnolipid in biofilm dispersion". Biofilms 1, n. 2 (aprile 2004): 91–99. http://dx.doi.org/10.1017/s147905050400119x.
Testo completoAbstract (sommario):
Biofilms are often considered as localized zones of high cell density. Quorum sensing provides a means for control of population processes and has been implicated in the regulation of biofilm activities. We present a role for quorum sensing in programmed detachment and dispersal processes. Biofilms of Pseudomonas aeruginosa PAO1 and its isogenic homoserine lactone (HSL) mutant P. aeruginosa PAO-JP2 were grown in batch culture on glass substrata; differences were found in the rate and extent of formation of biofilm. Climax communities were observed for PAO1 at 24 h. These were later accompanied by foaming, a drop in the surface tension of culture media and dispersal of the biofilm, after which no subsequent biofilm accretion occurred. PAO-JP2 cultures reformed biofilm post-detachment and did not foam. Prevention of biofilm reformation in the wild type was related to some component excreted into the culture medium. Rhamnolipid, a biosurfactant regulated by quorum sensing, was detected in PAO1 cultures. When rhamnolipid was added to freshly inoculated substrata, biofilm formation was inhibited. At 20 h, PAO1 biofilms were transferred to medium with added rhamnolipid: biofilm was relatively unaffected. Biofilm events were also studied in medium supplemented with N-butyryl-L-homoserine lactone, which is involved in the regulation of rhamnolipid synthesis. Both strains exhibited similar trends of rapid biofilm formation and dramatic changes in the rate and extent of biofilm accretion. In both cases, there was premature foaming, lowered surface tension and elevated rhamnolipid levels. A role for HSLs in maintenance of biofilm and events leading to dispersion of cells is proposed. This role would encompass dispersion but not necessarily detachment of cells from biofilm and supports a new function for rhamnolipid in pathogenesis, whereby rhamnolipid would promote the dissemination of cells from a nidus of infection.
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Frederick, Jesse R., James G. Elkins, Nikki Bollinger, Daniel J. Hassett e Timothy R. McDermott. "Factors Affecting Catalase Expression in Pseudomonas aeruginosa Biofilms and Planktonic Cells". Applied and Environmental Microbiology 67, n. 3 (1 marzo 2001): 1375–79. http://dx.doi.org/10.1128/aem.67.3.1375-1379.2001.
Testo completoAbstract (sommario):
ABSTRACT Previous work with Pseudomonas aeruginosa showed that catalase activity in biofilms was significantly reduced relative to that in planktonic cells. To better understand biofilm physiology, we examined possible explanations for the differential expression of catalase in cells cultured in these two different conditions. For maximal catalase activity, biofilm cells required significantly more iron (25 μM as FeCl3) in the medium, whereas planktonic cultures required no addition of iron. However, iron-stimulated catalase activity in biofilms was still only about one-third that in planktonic cells. Oxygen effects on catalase activity were also investigated. Nitrate-respiring planktonic cultures produced approximately twice as much catalase activity as aerobic cultures grown in the presence of nitrate; the nitrate stimulation effect could also be demonstrated in biofilms. Cultures fermenting arginine had reduced catalase levels; however, catalase repression was also observed in aerobic cultures grown in the presence of arginine. It was concluded that iron availability, but not oxygen availability, is a major factor affecting catalase expression in biofilms.
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MINEI, CLÁUDIA C., BRUNA C. GOMES, REGIANNE P. RATTI, CARLOS E. M. D'ANGELIS e ELAINE C. P. DE MARTINIS. "Influence of Peroxyacetic Acid and Nisin and Coculture with Enterococcus faecium on Listeria monocytogenes Biofilm Formation". Journal of Food Protection 71, n. 3 (1 marzo 2008): 634–38. http://dx.doi.org/10.4315/0362-028x-71.3.634.
Testo completoAbstract (sommario):
Biofilm formation is a matter of concern in food industries because biofilms facilitate the survival of pathogenic bacteria such as Listeria monocytogenes, which may contaminate food-processing equipment and products. In this study, nisin and two Enterococcus faecium strains were evaluated for their effect on biofilm formation by L. monocytogenes cultured in brain heart infusion broth and on stainless steel coupons. Elimination of preformed L. monocytogenes biofilms by peroxyacetic acid also was tested. Adhesion control experiments were performed with pure cultures of L. monocytogenes after swab collection of adhered cells, which were then enumerated on PALCAM agar plates and visualized by scanning electron microscopy. Formation of a biofilm was recorded when the number of adhered cells was at least 103 CFU/cm2. When L. monocytogenes was cocultured with E. faecium bac−, the number of adhered L. monocytogenes cells was 2.5 log lower (P = 0.002) when initially compared with the control culture, but after 6 h of incubation a biofilm was again detected. However, in coculture on stainless steel coupons, E. faecium bac+ inhibited L. monocytogenes adherence and did not allow biofilm formation for up to 48 h (P < 0.001). In the presence of nisin or after treatment with peroxyacetic acid, bacterial growth was reduced (P < 0.001) up to 4.6 and 5.6 log CFU/cm2, respectively, when compared with L. monocytogenes cultures on untreated coupons. However, after these treatments, cells were still present, and after 24 h of incubation, a renewed biofilm was detected in L. monocytogenes cultures treated with nisin. Although all tested conditions reduced L. monocytogenes growth to some extent, only coculture with E. faecium bac+ efficiently reduced biofilm formation, suggesting a potential control strategy for this pathogen.
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Vidal, Jorge E., Joshua R. Shak e Adrian Canizalez-Roman. "The CpAL Quorum Sensing System Regulates Production of Hemolysins CPA and PFO To Build Clostridium perfringens Biofilms". Infection and Immunity 83, n. 6 (30 marzo 2015): 2430–42. http://dx.doi.org/10.1128/iai.00240-15.
Testo completoAbstract (sommario):
Clostridium perfringensstrains produce severe diseases, including myonecrosis and enteritis necroticans, in humans and animals. Diseases are mediated by the production of potent toxins that often damage the site of infection, e.g., skin epithelium during myonecrosis. In planktonic cultures, the regulation of important toxins, such as CPA, CPB, and PFO, is controlled by theC. perfringensAgr-like (CpAL) quorum sensing (QS) system. Strains also encode a functional LuxS/AI-2 system. AlthoughC. perfringensstrains form biofilm-like structures, the regulation of biofilm formation is poorly understood. Therefore, our studies investigated the role of CpAL and LuxS/AI-2 QS systems and of QS-regulated factors in controlling the formation of biofilms. We first demonstrate that biofilm production by reference strains differs depending on the culture medium. Increased biomass correlated with the presence of extracellular DNA in the supernatant, which was released by lysis of a fraction of the biofilm population and planktonic cells. Whereas ΔagrBmutant strains were not able to produce biofilms, a ΔluxSmutant produced wild-type levels. The transcript levels of CpAL-regulatedcpaandpfoAgenes, but notcpb, were upregulated in biofilms compared to planktonic cultures. Accordingly, Δcpaand ΔpfoAmutants, in type A (S13) or type C (CN3685) backgrounds, were unable to produce biofilms, whereas CN3685Δcpbmade wild-type levels. Biofilm formation was restored in complemented Δcpa/cpaand ΔpfoA/pfoAstrains. Confocal microscopy studies further detected CPA partially colocalizing with eDNA on the biofilm structure. Thus, CpAL regulates biofilm formation inC. perfringensby increasing levels of certain toxins required to build biofilms.
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Wolyniak, E. A., B. R. Hargreaves e K. L. Jellison. "Retention and Release of Cryptosporidium parvum Oocysts by Experimental Biofilms Composed of a Natural Stream Microbial Community". Applied and Environmental Microbiology 75, n. 13 (15 maggio 2009): 4624–26. http://dx.doi.org/10.1128/aem.02916-08.
Testo completoAbstract (sommario):
ABSTRACT Cryptosporidium parvum oocysts accumulate on biofilm surfaces. The percentage of oocysts attached to biofilms remained nearly constant while oocysts were supplied to the system but decreased to a new steady-state level once oocysts were removed from the feed. More oocysts attached to summer biofilm cultures than winter biofilm cultures.
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Rahmani-Badi, Azadeh, Shayesteh Sepehr, Parisa Mohammadi, Mohammad Reza Soudi, Hamta Babaie-Naiej e Hossein Fallahi. "A combination of cis-2-decenoic acid and antibiotics eradicates pre-established catheter-associated biofilms". Journal of Medical Microbiology 63, n. 11 (1 novembre 2014): 1509–16. http://dx.doi.org/10.1099/jmm.0.075374-0.
Testo completoAbstract (sommario):
The catheterized urinary tract provides ideal conditions for the development of biofilm populations. Catheter-associated urinary tract infections (CAUTIs) are recalcitrant to existing antimicrobial treatments; therefore, established biofilms are not eradicated completely after treatment and surviving biofilm cells will carry on the infection. Cis-2-decenoic acid (CDA), an unsaturated fatty acid, is capable of inhibiting biofilm formation by Pseudomonas aeruginosa and of inducing the dispersion of established biofilms by multiple types of micro-organisms. Here, the ability of CDA to induce dispersal in pre-established single- and dual-species biofilms formed by Escherichia coli and Klebsiella pneumoniae was measured by using both semi-batch and continuous cultures bioassays. Removal of the biofilms by combined CDA and antibiotics (ciprofloxacin or ampicillin) was evaluated using microtitre plate assays (crystal violet staining). The c.f.u. counts were determined to assess the potential of combined CDA treatments to kill and eradicate pre-established biofilms formed on catheters. The effects of combined CDA treatments on biofilm surface area and bacteria viability were evaluated using fluorescence microscopy, digital image analysis and live/dead staining. To investigate the ability of CDA to prevent biofilm formation, single and mixed cultures were grown in the presence and absence of CDA. Treatment of pre-established biofilms with only 310 nM CDA resulted in at least threefold increase in the number of planktonic cells in all cultures tested. Whilst none of the antibiotics alone exerted a significant effect on c.f.u. counts and percentage of surface area covered by the biofilms, combined CDA treatments led to at least a 78 % reduction in biofilm biomass in all cases. Moreover, most of the biofilm cells remaining on the surface were killed by antibiotics. The addition of 310 nM CDA significantly prevented biofilm formation by the tested micro-organisms, even within mixed cultures, indicating the ability of CDA to inhibit biofilm formation by other types of bacteria in addition to Pseudomonas aeruginosa. These findings suggested that the biofilm-preventive characteristics of CDA make it a noble candidate for inhibition of biofilm-associated infections such as CAUTIs, which paves the way toward developing new strategies to control biofilms in clinical as well as industrial settings.
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Bryers, James D., e Huang Ching-Tsan. "Recombinant plasmid retention and expression in bacterial biofilm cultures". Water Science and Technology 31, n. 1 (1 gennaio 1995): 105–15. http://dx.doi.org/10.2166/wst.1995.0025.
Testo completoAbstract (sommario):
Any exposure of plasmid recombinant microorganisms to an open system environment, either inadvertently or intentionally, mandates research into those fundamental organism:plasmid processes that influence plasmid retention, transfer and expression. In open environmental systems a majority of the microbial activity occurs associated with an interface, within thin biological layers consisting of the cells and their insoluble extracellular polymer, layers known as biofilms. Thus any study regarding the fate of recombinant DNA sequences in an open system must consider processes that affect plasmid retention and expression in a biofilm culture. Biofilm cultures were cultivated in a parallel-plate flow cell reactor using E. coli DH5α which contained a recombinant plasmid with a plasmid stability factor, parB, (pTKW106) or without (pMJR1750). Using β-galactosidase as inducible reporter protein, plasmid retention and gene expression of pMJR1750 and pTKW106, in suspended versus biofilm cultures, were studied under different carbo to nitrogen ratios and plasmid induction levels. Recombinant biofilm formation under these environmental conditions was also investigated. Biofilm net accumulation rate of E. coli DH5α (pTKW106) decreases with increasing induction levels. The β-galactosidase production and ratios of β-galactosidase to total protein increase with increasing induction levels. Synthesis rates of total RNA, β-galactosidase mRNA and rRNA in biofilm cultures of E. coli DH5α (pTKW106) increase after induction by IPTG.
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Chinnici, Jennifer, Lisa Yerke, Charlene Tsou, Sujay Busarajan, Ryan Mancuso, Nishanth D. Sadhak, Jaewon Kim e Abhiram Maddi. "Candida albicans cell wall integrity transcription factors regulate polymicrobial biofilm formation with Streptococcus gordonii". PeerJ 7 (11 ottobre 2019): e7870. http://dx.doi.org/10.7717/peerj.7870.
Testo completoAbstract (sommario):
Polymicrobial biofilms play important roles in oral and systemic infections. The oral plaque bacterium Streptococcus gordonii is known to attach to the hyphal cell wall of the fungus Candida albicans to form corn-cob like structures in biofilms. However, the role of C. albicans in formation of polymicrobial biofilms is not completely understood. The objective of this study was to determine the role of C. albicans transcription factors in regulation of polymicrobial biofilms and antibiotic tolerance of S. gordonii. The proteins secreted by C. albicans and S. gordonii in mixed planktonic cultures were determined using mass spectrometry. Antibiotic tolerance of S. gordonii to ampicillin and erythromycin was determined in mixed cultures and mixed biofilms with C. albicans. Additionally, biofilm formation of S. gordonii with C. albicans knock-out mutants of 45 transcription factors that affect cell wall integrity, filamentous growth and biofilm formation was determined. Furthermore, these mutants were also screened for antibiotic tolerance in mixed biofilms with S. gordonii. Analysis of secreted proteomes resulted in the identification of proteins being secreted exclusively in mixed cultures. Antibiotic testing showed that S. gordonii had significantly increased survival in mixed planktonic cultures with antibiotics as compared to single cultures. C. albicans mutants of transcription factors Sfl2, Brg1, Leu3, Cas5, Cta4, Tec1, Tup1, Rim101 and Efg1 were significantly affected in mixed biofilm formation. Also mixed biofilms of S. gordonii with mutants of C. albicans transcription factors, Tec1 and Sfl2, had significantly reduced antibiotic tolerance as compared to control cultures. Our data indicates that C. albicans may have an important role in mixed biofilm formation as well as antibiotic tolerance of S. gordonii in polymicrobial biofilms. C. albicans may play a facilitating role than being just an innocent bystander in oral biofilms and infections.
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Kay, Matthew K., Thomas C. Erwin, Robert J. C. McLean e Gary M. Aron. "Bacteriophage Ecology inEscherichia coliandPseudomonas aeruginosaMixed-Biofilm Communities". Applied and Environmental Microbiology 77, n. 3 (3 dicembre 2010): 821–29. http://dx.doi.org/10.1128/aem.01797-10.
Testo completoAbstract (sommario):
ABSTRACTPhage therapy is being reexamined as a strategy for bacterial control in medical and other environments. As microorganisms often live in mixed populations, we examined the effect ofEscherichia colibacteriophage λW60 andPseudomonas aeruginosabacteriophage PB-1 infection on the viability of monoculture and mixed-species biofilm and planktonic cultures. In mixed-species biofilm communities,E. coliandP. aeruginosamaintained stable cell populations in the presence of one or both phages. In contrast,E. coliplanktonic populations were severely depleted in coculture in the presence of λW60. BothE. coliandP. aeruginosadeveloped phage resistance in planktonic culture; however, reduced resistance was observed in biofilm communities. Increased phage titers and reduced resistance in biofilms suggest that phage can replicate on susceptible cells in biofilms. Infectious phage could be released from mixed-culture biofilms upon treatment with Tween 20 but not upon treatment with chloroform. Tween 20 and chloroform treatments had no effect on phage associated with planktonic cells, suggesting that planktonic phage were not cell or matrix associated. Transmission electron microscopy showed bacteriophage particles to be enmeshed in the extracellular polymeric substance component of biofilms and that this substance could be removed by Tween 20 treatment. Overall, this study demonstrates how mixed-culture biofilms can maintain a reservoir of viable phage and bacterial populations in the environment.
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Chao, Jerry, Gideon M. Wolfaardt e Michael T. Arts. "Characterization of Pseudomonas aeruginosa fatty acid profiles in biofilms and batch planktonic cultures". Canadian Journal of Microbiology 56, n. 12 (dicembre 2010): 1028–39. http://dx.doi.org/10.1139/w10-093.
Testo completoAbstract (sommario):
The fatty acid composition of Pseudomonas aeruginosa PAO1 was compared between biofilm and batch planktonic cultures. Strain PAO1 biofilms were able to maintain a consistent fatty acid profile for up to 6 days, whereas strain PAO1 batch planktonic cultures showed a gradual loss of cis-monounsaturated fatty acids over 4 days. Biofilms exhibited a greater proportion of hydroxy fatty acids but a lower proportion of both cyclopropane fatty acids and saturated fatty acids (SAFAs). SAFAs with ≥16 carbons, in particular, decreased in biofilms when compared with that in batch planktonic cultures. A reduced proportion of SAFAs and a decline in overall fatty acid chain length indicate more fluidic biophysical properties for cell membranes of P. aeruginosa in biofilms. Separating the biofilms into 2 partitions and comparing their fatty acid compositions revealed additional trends that were not observed in the whole biofilm: the shear-nonremovable layer consistently showed greater proportions of hydroxy fatty acid than the bulk liquid + shear-removable portion of the biofilm. The shear-nonremovable portion demonstrated a relatively immediate decline in the proportion of monounsaturated fatty acids between days 2 and 4; which was offset by an increase in the proportion of cyclopropane fatty acids, specifically 19:0cyc(11,12). Simultaneously, the shear-removable portion of the biofilm showed an increase in the proportion of trans-monounsaturated fatty acids and cyclopropane fatty acids.
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Vacheva, Anna, Ralitsa Georgieva, Svetla Danova, Radka Mihova, Mariana Marhova, Sonia Kostadinova, Krasimira Vasileva, Maria Bivolarska e Stoyanka Stoitsova. "Modulation of Escherichia coli biofilm growth by cell-free spent cultures from lactobacilli". Open Life Sciences 7, n. 2 (1 aprile 2012): 219–29. http://dx.doi.org/10.2478/s11535-012-0004-9.
Testo completoAbstract (sommario):
AbstractE. coli biofilms cause serious problems in medical practice by contaminating surfaces and indwelling catheters. Due to the rapid development of antibiotic resistance, alternative approaches to biofilm suppression are needed. This study addresses whether products released by antagonistic bacteria — Lactobacillus isolates from vaginal and dairy-product samples could be useful for controlling E. coli biofilms. The effects of diluted cell-free supernatants (CFS) from late-exponential Lactobacillus cultures on the growth and biofilm production of Escherichia coli were tested. Most of the CFS applied as 10−2 had no impact on bacterial growth, biofilm development however was influenced even by 10−4 of CFS. Initial screening by crystal violet assay showed that biofilm modulation varied between different CFS and E. coli combinations from inhibition to activation; however three of the tested CFS showed consistency in biofilm suppression. This was not due to antibacterial activity since Live/Dead fluorescence labeling showed insignificant differences in the amount of dead cells in control and treated samples. Some E. coli strain-specific mechanisms of response to the three CFS included reduction in hydrophobicity and motility. Released exoploysaccharides isolated from the three CFS stimulated sessile growth, but proteinase K reduced their inhibitory activities implying participation of protein or peptide biofilm suppression factor(s).
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Rosca, Aliona S., Joana Castro e Nuno Cerca. "Evaluation of different culture media to support in vitro growth and biofilm formation of bacterial vaginosis-associated anaerobes". PeerJ 8 (10 settembre 2020): e9917. http://dx.doi.org/10.7717/peerj.9917.
Testo completoAbstract (sommario):
Background Bacterial vaginosis (BV) is one of the most common vaginal infections worldwide. It is associated with the presence of a dense polymicrobial biofilm on the vaginal epithelium, formed mainly by Gardnerella species. The biofilm also contains other anaerobic species, but little is known about their role in BV development. Aim To evaluate the influence of different culture media on the planktonic and biofilm growth of six cultivable anaerobes frequently associated with BV, namely Gardnerella sp., Atopobium vaginae, Lactobacillus iners, Mobiluncus curtisii, Peptostreptococcus anaerobius and Prevotella bivia. Methods A total of nine different culture media compositions, including commercially available and chemically defined media simulating genital tract secretions, were tested in this study. Planktonic cultures and biofilms were grown under anaerobic conditions (10% carbon dioxide, 10% helium and 80% nitrogen). Planktonic growth was assessed by optical density measurements, and biofilm formation was quantified by crystal violet staining. Results Significant planktonic growth was observed for Gardnerella sp., A. vaginae and L. iners in New York City III broth, with or without ascorbic acid supplementation. Biofilm quantification showed high in vitro biofilm growth for Gardnerella sp., P. anaerobius and P. bivia in almost all culture media excluding Brucella broth. Contrary, only New York City III broth was able to promote biofilm formation for A. vaginae, L. iners and M. curtisii. Conclusions Our data demonstrate that New York City III broth relative to the other tested media is the most conducive for future studies addressing polymicrobial biofilms development as this culture medium allowed the formation of significant levels of single-species biofilms.
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Behnke, Sabrina, Albert E. Parker, Dawn Woodall e Anne K. Camper. "Comparing the Chlorine Disinfection of Detached Biofilm Clusters with Those of Sessile Biofilms and Planktonic Cells in Single- and Dual-Species Cultures". Applied and Environmental Microbiology 77, n. 20 (19 agosto 2011): 7176–84. http://dx.doi.org/10.1128/aem.05514-11.
Testo completoAbstract (sommario):
ABSTRACTAlthough the detachment of cells from biofilms is of fundamental importance to the dissemination of organisms in both public health and clinical settings, the disinfection efficacies of commonly used biocides on detached biofilm particles have not been investigated. Therefore, the question arises whether cells in detached aggregates can be killed with disinfectant concentrations sufficient to inactivate planktonic cells.Burkholderia cepaciaandPseudomonas aeruginosawere grown in standardized laboratory reactors as single species and in coculture. Cluster size distributions in chemostats and biofilm reactor effluent were measured. Chlorine susceptibility was assessed for planktonic cultures, attached biofilm, and particles and cells detached from the biofilm. Disinfection tolerance generally increased with a higher percentage of larger cell clusters in the chemostat and detached biofilm. Samples with a lower percentage of large clusters were more easily disinfected. Thus, disinfection tolerance depended on the cluster size distribution rather than sample type for chemostat and detached biofilm. Intact biofilms were more tolerant to chlorine independent of species. Homogenization of samples led to significantly increased susceptibility in all biofilm samples as well as detached clusters for single-speciesB. cepacia,B. cepaciain coculture, andP. aeruginosain coculture. The disinfection efficacy was also dependent on species composition; coculture was advantageous to the survival of both species when grown as a biofilm or as clusters detached from biofilm but, surprisingly, resulted in a lower disinfection tolerance when they were grown as a mixed planktonic culture.
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Nuryastuti, Titik, Henny C. van der Mei, Henk J. Busscher, Susi Iravati, Abu T. Aman e Bastiaan P. Krom. "Effect of Cinnamon Oil on icaA Expression and Biofilm Formation by Staphylococcus epidermidis". Applied and Environmental Microbiology 75, n. 21 (11 settembre 2009): 6850–55. http://dx.doi.org/10.1128/aem.00875-09.
Testo completoAbstract (sommario):
ABSTRACT Staphylococcus epidermidis is notorious for its biofilm formation on medical devices, and novel approaches to prevent and kill S. epidermidis biofilms are desired. In this study, the effect of cinnamon oil on planktonic and biofilm cultures of clinical S. epidermidis isolates was evaluated. Initially, susceptibility to cinnamon oil in planktonic cultures was compared to the commonly used antimicrobial agents chlorhexidine, triclosan, and gentamicin. The MIC of cinnamon oil, defined as the lowest concentration able to inhibit visible microbial growth, and the minimal bactericidal concentration, the lowest concentration required to kill 99.9% of the bacteria, were determined using the broth microdilution method and plating on agar. A checkerboard assay was used to evaluate the possible synergy between cinnamon oil and the other antimicrobial agents. The effect of cinnamon oil on biofilm growth was studied in 96-well plates and with confocal laser-scanning microscopy (CLSM). Biofilm susceptibility was determined using a metabolic 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Real-time PCR analysis was performed to determine the effect of sub-MIC concentrations of cinnamon oil on expression of the biofilm-related gene, icaA. Cinnamon oil showed antimicrobial activity against both planktonic and biofilm cultures of clinical S. epidermidis strains. There was only a small difference between planktonic and biofilm MICs, ranging from 0.5 to 1% and 1 to 2%, respectively. CLSM images indicated that cinnamon oil is able to detach and kill existing biofilms. Thus, cinnamon oil is an effective antimicrobial agent to combat S. epidermidis biofilms.
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Villemur, Richard, Geneviève Payette, Valérie Geoffroy, Florian Mauffrey e Christine Martineau. "Dynamics of a methanol-fed marine denitrifying biofilm: 2—impact of environmental changes on the microbial community". PeerJ 7 (13 agosto 2019): e7467. http://dx.doi.org/10.7717/peerj.7467.
Testo completoAbstract (sommario):
Background The biofilm of a methanol-fed, marine denitrification system is composed of a multi-species microbial community, among which Hyphomicrobium nitrativorans and Methylophaga nitratireducenticrescens are the principal bacteria involved in the denitrifying activities. To assess its resilience to environmental changes, the biofilm was cultivated in artificial seawater (ASW) under anoxic conditions and exposed to a range of specific environmental conditions. We previously reported the impact of these changes on the denitrifying activities and the co-occurrence of H. nitrativorans strain NL23 and M. nitratireducenticrescens in the biofilm cultures. Here, we report the impact of these changes on the dynamics of the overall microbial community of the denitrifying biofilm. Methods The original biofilm (OB) taken from the denitrification system was cultivated in ASW under anoxic conditions with a range of NaCl concentrations, and with four combinations of nitrate/methanol concentrations and temperatures. The OB was also cultivated in the commercial Instant Ocean seawater (IO). The bacterial diversity of the biofilm cultures and the OB was determined by 16S ribosomal RNA gene sequences. Culture approach was used to isolate other denitrifying bacteria from the biofilm cultures. The metatranscriptomes of selected biofilm cultures were derived, along with the transcriptomes of planktonic pure cultures of H. nitrativorans strain NL23 and M. nitratireducenticrescens strain GP59. Results High proportions of M. nitratireducenticrescens occurred in the biofilm cultures. H. nitrativorans strain NL23 was found in high proportion in the OB, but was absent in the biofilm cultures cultivated in the ASW medium at 2.75% NaCl. It was found however in low proportions in the biofilm cultures cultivated in the ASW medium at 0–1% NaCl and in the IO biofilm cultures. Denitrifying bacterial isolates affiliated to Marinobacter spp. and Paracoccus spp. were isolated. Up regulation of the denitrification genes of strains GP59 and NL23 occurred in the biofilm cultures compared to the planktonic pure cultures. Denitrifying bacteria affiliated to the Stappia spp. were metabolically active in the biofilm cultures. Conclusions These results illustrate the dynamics of the microbial community in the denitrifying biofilm cultures in adapting to different environmental conditions. The NaCl concentration is an important factor affecting the microbial community in the biofilm cultures. Up regulation of the denitrification genes of M. nitratireducenticrescens strain GP59 and H. nitrativorans strain NL23 in the biofilm cultures suggests different mechanisms of regulation of the denitrification pathway in the biofilm. Other denitrifying heterotrophic bacteria are present in low proportions, suggesting that the biofilm has the potential to adapt to heterotrophic, non-methylotrophic environments.
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Roberts, Mark E., e Philip S. Stewart. "Modelling protection from antimicrobial agents in biofilms through the formation of persister cells". Microbiology 151, n. 1 (1 gennaio 2005): 75–80. http://dx.doi.org/10.1099/mic.0.27385-0.
Testo completoAbstract (sommario):
A mathematical model of biofilm dynamics was used to investigate the protection from antimicrobial killing that could be afforded to micro-organisms in biofilms based on a mechanism of ‘persister’ cell or phenotypic variant formation. The persister state is a hypothetical, highly protected state adopted by a small fraction of the cells in a biofilm. Persisters were assumed to be generated at a fixed rate, independent of the presence of substrate or antimicrobial agent. Cells were assumed to revert from the persister state when exposed to the growth substrate. Persister cells were assumed to be incapable of growth. The model predicted that persister cells increased in numbers in the biofilm, even though they were unable to grow, accumulating in regions of substrate limitation. In these regions, normal cells failed to grow, but did slowly convert to the persister state. Calculations of persister formation in planktonic cultures predicted that persisters would be present in low numbers in growing cultures, but should accumulate under conditions of slow growth, e.g. very low dilution rates in continuous culture or stationary phase in batch culture. When antibiotic treatment was simulated, bacteria near the biofilm surface were killed, but persisters in the depth of the biofilm were poorly killed. After antibiotic treatment ceased, surviving persister cells quickly reverted and allowed the biofilm to regrow. This modelling study provides motivation for further investigation of the hypothetical persister cell state as an explanation for biofilm resistance to antimicrobial agents.
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Vieira, M. J., e L. F. Melo. "Effect of clay particles on the behaviour of biofilms formed by Pseudomonas fluorescens". Water Science and Technology 32, n. 8 (1 ottobre 1995): 45–52. http://dx.doi.org/10.2166/wst.1995.0260.
Testo completoAbstract (sommario):
This paper presents results obtained with biofilms formed under turbulent flow by a mixed suspension of Pseudomonas fluorescens and kaolin particles and compares them with biofilms formed in the absence of clay particles. The results show that the presence of kaolin particles leads to: higher accumulation of biomass in biofilm systems; higher stability of the biofilms when substrate is suppressed; higher values of the respiratory coefficient of the suspended cell cultures; increase in the mass transfer rates throughout the biofilm thickness. The results suggest that the kaolin particles enhance microbial activity in the biofilm and may cause changes in the physical structure of the biofilm, making it a more strong and open matrix.
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Navarrete, Fernando, e Leonardo De La Fuente. "Response of Xylella fastidiosa to Zinc: Decreased Culturability, Increased Exopolysaccharide Production, and Formation of Resilient Biofilms under Flow Conditions". Applied and Environmental Microbiology 80, n. 3 (22 novembre 2013): 1097–107. http://dx.doi.org/10.1128/aem.02998-13.
Testo completoAbstract (sommario):
ABSTRACTThe bacterial plant pathogenXylella fastidiosaproduces biofilm that accumulates in the host xylem vessels, affecting disease development in various crops and bacterial acquisition by insect vectors. Biofilms are sensitive to the chemical composition of the environment, and mineral elements being transported in the xylem are of special interest for this pathosystem. Here,X. fastidiosaliquid cultures were supplemented with zinc and compared with nonamended cultures to determine the effects of Zn on growth, biofilm, and exopolysaccharide (EPS) production under batch and flow culture conditions. The results show that Zn reduces growth and biofilm production under both conditions. However, in microfluidic chambers under liquid flow and with constant bacterial supplementation (closer to conditions inside the host), a dramatic increase in biofilm aggregates was seen in the Zn-amended medium. Biofilms formed under these conditions were strongly attached to surfaces and were not removed by medium flow. This phenomenon was correlated with increased EPS production in stationary-phase cells grown under high Zn concentrations. Zn did not cause greater adhesion to surfaces by individual cells. Additionally, viability analyses suggest thatX. fastidiosamay be able to enter the viable but nonculturable statein vitro, and Zn can hasten the onset of this state. Together, these findings suggest that Zn can act as a stress factor with pleiotropic effects onX. fastidiosaand indicate that, although Zn could be used as a bactericide treatment, it could trigger the undesired effect of stronger biofilm formation upon reinoculation events.
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Thomas, Vinai Chittezham, Lance R. Thurlow, Dan Boyle e Lynn E. Hancock. "Regulation of Autolysis-Dependent Extracellular DNA Release by Enterococcus faecalis Extracellular Proteases Influences Biofilm Development". Journal of Bacteriology 190, n. 16 (13 giugno 2008): 5690–98. http://dx.doi.org/10.1128/jb.00314-08.
Testo completoAbstract (sommario):
ABSTRACT Enterococci are major contributors of hospital-acquired infections and have emerged as important reservoirs for the dissemination of antibiotic resistance traits. The ability to form biofilms on medical devices is an important aspect of pathogenesis in the hospital environment. The Enterococcus faecalis Fsr quorum system has been shown to regulate biofilm formation through the production of gelatinase, but the mechanism has been hitherto unknown. Here we show that both gelatinase (GelE) and serine protease (SprE) contribute to biofilm formation by E. faecalis and provide clues to how the activity of these proteases governs this developmental process. Confocal imaging of biofilms suggested that GelE− mutants were significantly reduced in biofilm biomass compared to the parental strain, whereas the absence of SprE appeared to accelerate the progression of biofilm development. The phenotype observed in a SprE− mutant was linked to an observed increase in autolytic rate compared to the parental strain. Culture supernatant analysis and confocal microscopy confirmed the inability of mutants deficient in GelE to release extracellular DNA (eDNA) in planktonic and biofilm cultures, whereas cells deficient in SprE produced significantly more eDNA as a component of the biofilm matrix. DNase I treatment of E. faecalis biofilms reduced the accumulation of biofilm, implying a critical role for eDNA in biofilm development. In conclusion, our data suggest that the interplay of two secreted and coregulated proteases—GelE and SprE—is responsible for regulating autolysis and the release of high-molecular-weight eDNA, a critical component for the development of E. faecalis biofilms.
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Darmasiwi, Sari, Oktaviana Herawati e Endah Retnaningrum. "Edible biofilm formation from guava seed waste fermentation". Digital Press Physical Sciences and Engineering 1 (2018): 00005. http://dx.doi.org/10.29037/digitalpress.11244.
Testo completoAbstract (sommario):
Guava seed is by-product from the consumption of guava fruits. We interested to explore further the potential of guava seed waste using fermentation method. The purpose of this research was to determine the ability of biofilm formation produced from fermentation of guava seed. Fermented guava seed was prepared by solid-state fermentation method using banana leaves wrap at 37 °C for 72 h. It were then continued with isolation and screening of bacteria from the fermentation products, preparation of bacteria cultures to be used in biofilm formation, and formation of biofilm by glass slides and broth cultures methods. The edible biofilm formation by glass slide method was observed by light microscopy using 0.5 % Crystal Violet dye, while biofilm formation by broth cultures method was observed by transmission electron microscopy (TEM) using phosphotungstic acid 2 % dye. The results show that there were 3 (three) strains lactic acid bacteria (LAB) candidates isolated from fermented guava seed waste product (J6, J7, and J8 strains). The observation by light microscopy showed that J7 strain was the only strain which was unable to form biofilm by glass slide method. All the strains showed the ability to form biofilms in different stages by broth cultures method. Thus, guava seed fermentation was able to produce edible biofilm but the LAB strains still need to be identified further.<br>
22
Verkholyuk, Mykola, Ruslan Peleno e Iaromyr Turko. "RESISTANCE OF S. AUREUS ATCC 25923, E. COLI 055K59 No. 3912/41 AND P. AERUGINOSA 27/99 TO THE WASH-DISINFECTANT «MILKODEZ»". EUREKA: Health Sciences 1 (31 gennaio 2020): 55–60. http://dx.doi.org/10.21303/2504-5679.2020.001100.
Testo completoAbstract (sommario):
The aim of the work – the article presents the results of determining of the resistance of S. aureus ATCC 25923, E. coli 055K59 No. 3912/4 and P. aeruginosa 27/99 test cultures in planktonic form and in biofilm to our developed «Milkodez» acid detergent. Materials and methods. Microbial biofilms were grown on MPB in 5 cm disposable plastic Petri dishes. To determine the effect of disinfectants on microbial biofilms, 3 Petri dishes with biofilms of each of the test cultures were used. One of the Petri dishes served as control and she had for 15 minutes made 5 cm3 of saline NaCl solution, in the second – 5 cm3 of hot water (t=70±5 °C), and in the third – 5 cm3 of acidic detergent «Milkodez». Microbial biofilms were fixed for 10 min. 96º with ethyl alcohol for 10 min. were stained with a 0.1 % solution of crystalline violet, and the remnants of the unabsorbed paint were removed with phosphate buffer. The biofilm dye was extracted with 96º of ethyl alcohol, which was photocolometrically investigated at 570 nm to establish the density of the formed biofilms. The density of the formed microbial biofilms was considered low in optical density of the extract up to 0.5 units, average – from 0.5 to 1.0 units; and high – over 1.0 units The resistance of planktonic forms of test cultures of microorganisms to disinfectants was determined in sterile tubes, which made 10 cm3 (t=70±5 °C) of 0.5 % of their working solutions and 0.1 cm3 (1 billion microbial bodies) of the standard test – cultures. The culture was maintained for 15 min. and made ten – fold plantings on IPA in Petri dishes. Incubation of mesophilic microorganisms was carried out in a thermostat at a temperature of 30 °C, and psychrophilic – 20 °C. After 48 hours the calculation of the growing colonies were carried out. The results were expressed in colony forming units (CFU). Results. Due to the impact on microbial biofilms formed by the test cultures of S. aureus ATCC 25923, E. coli 055K59 No. 3912/41 and P. aeruginosa 27/99 for 15 min. 0.5 % solution of acid detergent «Milkodez» the optical density of the solutions was respectively 0.64, 0.72, 0.45 units. The results obtained indicate that the melkodez caused a decrease in the biofilm–forming ability of S. aureus ATCC 25923 3.2 times, in E. coli 055K59 No. 3912/41 – 1,7 times and in P. aeruginosa 27/99 – 2.8 times, compared to control. However, the density of one – day microbial biofilms formed by S. aureus ATCC 25923 and E. coli 055K59 No. 3912/41 was medium, and P. aeruginosa 27/99 was low. It has been proven that the «Milkodez» acid detergent developed is more effective than the prototype «Hypracid», since it caused the death of 100 % of planktonic test cultures and the number of S. aureus ATCC 25923, E. coli 055K59 No. 3912/41 and P. aeruginosa 27/99 formed in the biofilm that survived after its application was 2.7, 3.2 and 1.4 times lower, respectively. Conclusions. It was found that the test cultures were able to form high – density biofilms, since the optical density of the extract in the control was in the range from 1.28 to 2.05 units, which is greater than 1.0 units. Acid wash detergent «Milkodez» for 15 minutes of exposure causes the formation of S. aureus ATCC 25923, E. coli 055K59 No. 3912/41 and P. aeruginosa 27/99 biofilms of low and medium density and reduces their biofilm capacity by 3.2, 1.7 and 2.8 times, respectively. Its use provides the death of 100 % of the planktonic forms of the test cultures under study and reduces their number in the biofilm by 2.7, 3.2 and 1,4 times more, respectively, compared to «Hypracid» detergent.
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Webb, Jeremy S., Mathew Lau e Staffan Kjelleberg. "Bacteriophage and Phenotypic Variation in Pseudomonas aeruginosa Biofilm Development". Journal of Bacteriology 186, n. 23 (1 dicembre 2004): 8066–73. http://dx.doi.org/10.1128/jb.186.23.8066-8073.2004.
Testo completoAbstract (sommario):
ABSTRACT A current question in biofilm research is whether biofilm-specific genetic processes can lead to differentiation in physiology and function among biofilm cells. In Pseudomonas aeruginosa, phenotypic variants which exhibit a small-colony phenotype on agar media and a markedly accelerated pattern of biofilm development compared to that of the parental strain are often isolated from biofilms. We grew P. aeruginosa biofilms in glass flow cell reactors and observed that the emergence of small-colony variants (SCVs) in the effluent runoff from the biofilms correlated with the emergence of plaque-forming Pf1-like filamentous phage (designated Pf4) from the biofilm. Because several recent studies have shown that bacteriophage genes are among the most highly upregulated groups of genes during biofilm development, we investigated whether Pf4 plays a role in SCV formation during P. aeruginosa biofilm development. We carried out immunoelectron microscopy using anti-Pf4 antibodies and observed that SCV cells, but not parental-type cells, exhibited high densities of Pf4 filaments on the cell surface and that these filaments were often tightly interwoven into complex latticeworks surrounding the cells. Moreover, infection of P. aeruginosa planktonic cultures with Pf4 caused the emergence of SCVs within the culture. These SCVs exhibited enhanced attachment, accelerated biofilm development, and large regions of dead and lysed cells inside microcolonies in a manner identical to that of SCVs obtained from biofilms. We concluded that Pf4 can mediate phenotypic variation in P. aeruginosa biofilms. We also performed partial sequencing and analysis of the Pf4 replicative form and identified a number of open reading frames not previously recognized in the genome of P. aeruginosa, including a putative postsegregational killing operon.
24
West-Barnette, Shayla, Andrea Rockel e W. Edward Swords. "Biofilm Growth Increases Phosphorylcholine Content and Decreases Potency of Nontypeable Haemophilus influenzae Endotoxins". Infection and Immunity 74, n. 3 (marzo 2006): 1828–36. http://dx.doi.org/10.1128/iai.74.3.1828-1836.2006.
Testo completoAbstract (sommario):
ABSTRACT Nontypeable Haemophilus influenzae (NTHI) is a common respiratory commensal and opportunistic pathogen. NTHI is normally contained within the airways by host innate defenses that include recognition of bacterial endotoxins by Toll-like receptor 4 (TLR4). NTHI produces lipooligosaccharide (LOS) endotoxins which lack polymeric O side chains and which may contain host glycolipids. We recently showed that NTHI biofilms contain variants with sialylated LOS glycoforms that are essential to biofilm formation. In this study, we show that NTHI forms biofilms on epithelial cell layers. Confocal analysis revealed that sialylated variants were distributed throughout the biofilm, while variants expressing phosphorylcholine (PCho) were found within the biofilm. Consistent with this observation, PCho content of LOS purified from NTHI biofilms was increased compared to LOS from planktonic cultures. Hypothesizing that the observed changes in endotoxin composition could affect bioactivity, we compared inflammatory responses to NTHI LOS purified from biofilm and planktonic cultures. Our results show that endotoxins from biofilms induced weaker host innate responses. While we observed a minimal effect of sialylation on LOS bioactivity, there was a significant decrease in bioactivity associated with PCho substitutions. We thus conclude that biofilm growth increases the proportion of PCho+ variants in an NTHI population, resulting in a net decrease in LOS bioactivity. Thus, in addition to their well-documented resistance phenotypes, our data show that biofilm communities of NTHI bacteria contain variants that evoke less potent host responses.
25
Dohare, Suhaga, Devendra Singh, Deepmala Sharma e Vishnu Agarwal. "EFFECT OF Staphylococcus epidermidis ON Pseudomonas aeruginosa BIOFILM IN MIXED-SPECIES CULTURE". Journal of Experimental Biology and Agricultural Sciences 9, n. 3 (25 giugno 2021): 325–34. http://dx.doi.org/10.18006/2021.9(3).325.334.
Testo completoAbstract (sommario):
Staphylococcus epidermidis and Pseudomonas aeruginosa, are clinically relevant pathogens that often produce biofilms. To investigate the co-survivability of S. epidermidis and P. aeruginosa in mixed cultures biofilm and planktonic form, it is important to understand more about the interspecies interaction of both species. The interspecies interaction was analyzed using streak and drop agar plate assay, cell viability assay (CFU), spectrophotometry-based method, and microscopic analysis. The findings suggest that both cells and supernatant of P. aeruginosa inhibit the planktonic growth of S. epidermidis. The cell viability result shows that PAO1 biofilm cells were decreased by 88%, and SE biofilm cells were increased by 75% concerning their control. Opposite to the P. aeruginosa, the S. epidermidis biofilm and EPS matrix were found to increase in mixed culture biofilm, which was further confirmed by microscopic analysis. In contrast, differential agar media result shows that the reduction in the biofilm (CFU/ml) of P. aeruginosa is independent of S. epidermidis cells concentration. Finally, the effect of the supernatant on biofilm was investigated, and it found that S. epidermidis biofilm was enhanced while P. aeruginosa biofilm was reduced in the presence of partner bacterial supernatant, which indicated that S. epidermidis in biofilm mode could hinder the biofilm formation of P. aeruginosa. The outcomes show that the culture supernatant of S. epidermidis can be used to prevent P. aeruginosa associated biofilm infections.
26
Henry-Stanley, Michelle J., Donavon J. Hess e Carol L. Wells. "Aminoglycoside inhibition of Staphylococcus aureus biofilm formation is nutrient dependent". Journal of Medical Microbiology 63, n. 6 (1 giugno 2014): 861–69. http://dx.doi.org/10.1099/jmm.0.068130-0.
Testo completoAbstract (sommario):
Biofilms represent microbial communities, encased in a self-produced matrix or extracellular polymeric substance. Microbial biofilms are likely responsible for a large proportion of clinically significant infections and the multicellular nature of biofilm existence has been repeatedly associated with antibiotic resistance. Classical in vitro antibiotic-susceptibility testing utilizes artificial growth media and planktonic microbes, but this method may not account for the variability inherent in environments subject to biofilm growth in vivo. Experiments were designed to test the hypothesis that nutrient concentration can modulate the antibiotic susceptibility of Staphylococcus aureus biofilms. Developing S. aureus biofilms initiated on surgical sutures, and in selected experiments planktonic cultures, were incubated for 16 h in 66 % tryptic soy broth, 0.2 % glucose (1× TSBg), supplemented with bactericidal concentrations of gentamicin, streptomycin, ampicillin or vancomycin. In parallel experiments, antibiotics were added to growth medium diluted one-third (1/3× TSBg) or concentrated threefold (3× TSBg). Following incubation, viable bacteria were enumerated from planktonic cultures or suture sonicates, and biofilm biomass was assayed using spectrophotometry. Interestingly, bactericidal concentrations of gentamicin (5 µg gentamicin ml−1) and streptomycin (32 µg streptomycin ml−1) inhibited biofilm formation in samples incubated in 1/3× or 1× TSBg, but not in samples incubated in 3× TSBg. The nutrient dependence of aminoglycoside susceptibility is not only associated with biofilm formation, as planktonic cultures incubated in 3× TSBg in the presence of gentamicin also showed antibiotic resistance. These findings appeared specific for aminoglycosides because biofilm formation was inhibited in all three growth media supplemented with bactericidal concentrations of the cell wall-active antibiotics, ampicillin and vancomycin. Additional experiments showed that the ability of 3× TSBg to overcome the antibacterial effects of gentamicin was associated with decreased uptake of gentamicin by S. aureus. Uptake is known to be decreased at low pH, and the kinetic change in pH of growth medium from biofilms incubated in 5 µg gentamicin ml−1 in the presence of 3× TSBg was decreased when compared with pH determinations from biofilms formed in 1/3× or 1× TSBg. These studies underscore the importance of environmental factors, including nutrient concentration and pH, on the antibiotic susceptibility of S. aureus planktonic and biofilm bacteria.
27
Koch, John A., Taylor M. Pust, Alex J. Cappellini, Jonathan B. Mandell, Dongzhu Ma, Neel B. Shah, Kimberly M. Brothers e Kenneth L. Urish. "Staphylococcus epidermidis Biofilms Have a High Tolerance to Antibiotics in Periprosthetic Joint Infection". Life 10, n. 11 (24 ottobre 2020): 253. http://dx.doi.org/10.3390/life10110253.
Testo completoAbstract (sommario):
Both Staphylococcus aureus and Staphylococcus epidermidis are commonly associated with periprosthetic joint infections (PJIs). The treatment of PJI can be challenging because biofilms are assumed to have an increased intolerance to antibiotics. This makes the treatment of PJI challenging from a clinical perspective. Although S. aureus has been previously demonstrated to have increased biofilm antibiotic tolerance, this has not been well established with Staphylococcus epidermidis. A prospective registry of PJI S. epidermidis isolates was developed. The efficacy of clinically relevant antibiotics was quantified against these isolates. S. epidermidis planktonic minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were collected using clinical laboratory standard index (CLSI) assays for eight antibiotics (doxycycline, vancomycin, daptomycin, clindamycin, rifampin, nafcillin, and trimethoprim/sulfamethoxazole). Mature biofilms were grown in vitro, after which minimum biofilm inhibitory concentration (MBIC) and minimum biofilm bactericidal concentration (MBBC) were quantified. Only rifampin and doxycycline had a measurable MBIC across all tested isolates. Based on MBBC, 64% of S. epidermidis biofilms could be eliminated by rifampin, whereas only 18% by doxycycline. S. epidermidis biofilm was observed to have a high tolerance to antibiotics as compared to planktonic culture. Isolate biofilm antibiotic tolerance varied to a larger degree than was seen in planktonic cultures.
28
Liu, Zhi, Fiona R. Stirling e Jun Zhu. "Temporal Quorum-Sensing Induction Regulates Vibrio cholerae Biofilm Architecture". Infection and Immunity 75, n. 1 (30 ottobre 2006): 122–26. http://dx.doi.org/10.1128/iai.01190-06.
Testo completoAbstract (sommario):
ABSTRACT Vibrio cholerae, the pathogen that causes cholera, also survives in aqueous reservoirs, probably in the form of biofilms. Quorum sensing negatively regulates V. cholerae biofilm formation through HapR, whose expression is induced at a high cell density. In this study, we show that the concentration of the quorum-sensing signal molecule CAI-1 is higher in biofilms than in planktonic cultures. By measuring hapR expression and activity, we found that the induction of quorum sensing in biofilm-associated cells occurs earlier. We further demonstrate that the timing of hapR expression is crucial for biofilm thickness, biofilm detachment rates, and intestinal colonization efficiency. These results suggest that V. cholerae is able to regulate its biofilm architecture by temporal induction of quorum-sensing systems.
29
Cholo, Moloko C., Sipho S. M. Rasehlo, Eudri Venter, Chantelle Venter e Ronald Anderson. "Effects of Cigarette Smoke Condensate on Growth and Biofilm Formation by Mycobacterium tuberculosis". BioMed Research International 2020 (19 agosto 2020): 1–7. http://dx.doi.org/10.1155/2020/8237402.
Testo completoAbstract (sommario):
Background and Objectives. Cigarette smoke (CS) is a major risk factor contributing to the burden of tuberculosis. Little is known, however, about the effects of CS exposure on growth and persistence of Mycobacterium tuberculosis (Mtb) organisms. This issue has been addressed in the current study, which is focused on the effects of cigarette smoke condensate (CSC) on the growth and viability of Mtb planktonic and biofilm-forming cultures. Materials and Methods. The planktonic and biofilm-forming cultures were prepared in Middlebrook 7H9 and Sauton broth media, respectively, using Mtb strain, H37Rv. The effects of CSC at concentrations of 0.05-3.12 mg/L on growth, biofilm formation and structure were evaluated using microplate Alamar Blue assay, spectrophotometric procedure and scanning electron microscopy (SEM), respectively. Involvement of reactive oxygen species in CSC-mediated biofilm formation was investigated by including catalase in biofilm-forming cultures. Results. CSC did not affect the growth of planktonic bacteria, but rather led to a statistically significant increase in biofilm formation at concentrations of 0.4-3.12 mg/L, as well as in the viability of biofilm-forming bacteria at CSC concentrations of 0.2-1.56 mg/L. SEM confirmed an agglomerated biofilm matrix and irregular bacterial morphology in CSC-treated biofilms. Inclusion of catalase caused significant attenuation of CSC-mediated augmentation of biofilm formation by Mtb, implying involvement of oxidative stress. These findings demonstrate that exposure of Mtb to CSC resulted in increased biofilm formation that appeared to be mediated, at least in part, by oxidative stress, while no effect on planktonic cultures was observed. Conclusion. Smoking-related augmentation of biofilm formation by Mtb may contribute to persistence of the pathogen, predisposing to disease reactivation and counteracting the efficacy of antimicrobial chemotherapy.
30
Maggio, Francesca, Chiara Rossi, Clemencia Chaves-López, Annalisa Serio, Luca Valbonetti, Francesco Pomilio, Alessio Pio Chiavaroli e Antonello Paparella. "Interactions between L. monocytogenes and P. fluorescens in Dual-Species Biofilms under Simulated Dairy Processing Conditions". Proceedings 70, n. 1 (9 novembre 2020): 80. http://dx.doi.org/10.3390/foods_2020-07625.
Testo completoAbstract (sommario):
In dairy processing environments, many bacterial species form biofilms on surfaces and equipment. Among them, Listeria monocytogenes and Pseudomonas spp. could be present in mixed-species biofilms with increased resistance to disinfectants. This study aimed to evaluate the interactions between L. monocytogenes and P. fluorescens in dual-species biofilms simulating dairy processing conditions as well as the capability of P. fluorescens to produce the blue pigment. The biofilm-forming capability of single- and mixed-cultures was evaluated on polystyrene (PS) and stainless steel (SS) surfaces at 12 °C for 168 h. Biofilm biomass was assessed by crystal violet staining, the planktonic and sessile cells were quantified in terms of Colony Forming Unit (CFU), and the carbohydrates were quantified by the anthrone method. The biofilms were also observed through Confocal Laser Scanning Microscopy (CLSM) analysis. Results showed that only P. fluorescens was able to form biofilms on PS. In dual-species biofilms at the end of the incubation time, a lower biomass compared to P. fluorescens mono-species was observed. On the SS, the biofilm cell population of L. monocytogenes was higher in the dual-species than in the mono-species, particularly after 48 h. Carbohydrates in the dual-species system were higher than those of the mono-species and were also revealed at 168 h. The production of blue pigment by P. fluorescens in the Ricotta-based model system was revealed in both single cultures and co-cultures and was confirmed by the CLSM results, showing agglomeration, probably linked to the blue pigment. Our study suggests that the interactions between the two species can influence biofilm formation, but not the capability of P. fluorescens to produce blue pigment.
31
Ramalingam, B., R. Sekar, J. B. Boxall e C. A. Biggs. "Aggregation and biofilm formation of bacteria isolated from domestic drinking water". Water Supply 13, n. 4 (1 agosto 2013): 1016–23. http://dx.doi.org/10.2166/ws.2013.115.
Testo completoAbstract (sommario):
The objective of this study was to investigate the autoaggregation, coaggregation and biofilm formation of four bacteria namely Sphingobium, Xenophilus, Methylobacterium and Rhodococcus isolated from drinking water. Auto and coaggregation studies were performed by both qualitative (DAPI staining) and semi-quantitative (visual coaggregation) methods and biofilms produced by either pure or dual-cultures were quantified by crystal violet method. Results from the semi-quantitative visual aggregation method did not show any immediate auto or coaggregation, which was confirmed by the 4′,6 diamidino-2-phenylindole (DAPI) staining method. However, after 2 hours, Methylobacterium showed the highest autoaggregation of all four isolates. The Methylobacterium combinations showed highest coaggregation between dual species at extended period of times (72 hours). Biofilm formation by pure cultures was negligible in comparison to the quantity of biofilm produced by dual-species biofilms. The overall results show that coaggregation of bacteria isolated from drinking water was mediated by species-specific and time-dependent interactions with a synergistic type of biofilm formation. The results of this study are therefore a useful step in assisting the development of potential control strategies by identifying specific bacteria that promote aggregation or biofilm formation in drinking water distribution systems.
32
Schafer, Mark E., e Tessie McNeely. "Combining Visible Light and Non-Focused Ultrasound Significantly Reduces Propionibacterium acnes Biofilm While Having Limited Effect on Host Cells". Microorganisms 9, n. 5 (26 aprile 2021): 929. http://dx.doi.org/10.3390/microorganisms9050929.
Testo completoAbstract (sommario):
Bacterial biofilms are highly resistant to antibiotics and have been implicated in the etiology of 60%–80% of chronic microbial infections. We tested a novel combination of low intensity ultrasound and blue light against biofilm and planktonic bacteria. A laboratory prototype was built which produced both energies uniformly and coincidently from a single treatment head, impinging upon a 4.45 cm2 target. To demonstrate proof of concept, Propionibacterium acnes biofilms were cultured on Millicell hanging inserts in 6-well plates. Hanging inserts with biofilms were treated in a custom exposure chamber designed to minimize unwanted ultrasound reflections. Coincident delivery of both energies demonstrated synergy over either alone, killing both stationary planktonic and biofilm cultures of P. acnes. Reduction in biofilm bacteria was dose dependent on exposure time (i.e., energy delivered). P. acnes biofilms were significantly reduced by dual energy treatment (p < 0.0001), with a >1 log10 reduction after a 5 min (9 J/cm2) and >3 log10 reduction after a 30 min (54 J/cm2) treatment (p < 0.05). Mammalian cells were found to be unaffected by the treatment. Both the light and the ultrasound energies are at levels previously cleared by the FDA. Therefore, this combination treatment could be used as a safe, efficacious method to treat biofilm related syndromes.
33
Kuznetsova, Marina V., Irina L. Maslennikova, Tamara I. Karpunina, Larisa Yu Nesterova e Vitaly A. Demakov. "Interactions of Pseudomonas aeruginosa in predominant biofilm or planktonic forms of existence in mixed culture with Escherichia coli in vitro". Canadian Journal of Microbiology 59, n. 9 (settembre 2013): 604–10. http://dx.doi.org/10.1139/cjm-2013-0168.
Testo completoAbstract (sommario):
Pseudomonas aeruginosa and Escherichia coli are known to be involved in mixed communities in diverse niches. In this study we examined the influence of the predominant form of cell existence of and the exometabolite production by P. aeruginosa strains on interspecies interactions, in vitro. Bacterial numbers of P. aeruginosa and E. coli in mixed plankton cultures and biofilms compared with their numbers in single plankton cultures and biofilms changed in a different way, but were in accordance with the form of P. aeruginosa cell existence. The mass of a mixed-species biofilm was greater than the mass of a single-species biofilm. Among the mixed biofilms, the one with the “planktonic” P. aeruginosa strain had the least biomass. The total pyocyanin and pyoverdin levels were found to be lower in all mixed plankton cultures. Despite this, clinical P. aeruginosa strains irrespective of the predominant form of existence (“biofilm” or “planktonic”) had a higher total concentration of exometabolites than did the reference strain in 12–24 h mixed cultures. The metabolism of E. coli, according to its bioluminescence, was reduced in mixed cultures, and the decrease was by 20- to 100-fold greater with the clinical Pseudomonas strains than the reference Pseudomonas strain. Thus, both the predominant form of existence of and the exometabolite production by distinct P. aeruginosa strains should be considered to fully understand the interspecies relationship and bacteria survival in natural communities.
34
Payette, Geneviève, Valérie Geoffroy, Christine Martineau e Richard Villemur. "Dynamics of a methanol-fed marine denitrifying biofilm: 1-Impact of environmental changes on the denitrification and the co-occurrence of Methylophaga nitratireducenticrescens and Hyphomicrobium nitrativorans". PeerJ 7 (13 agosto 2019): e7497. http://dx.doi.org/10.7717/peerj.7497.
Testo completoAbstract (sommario):
Background The biofilm of a methanol-fed denitrification system that treated a marine effluent is composed of multi-species microorganisms, among which Hyphomicrobium nitrativorans strain NL23 and Methylophaga nitratireducenticrescens strain JAM1 are the principal bacteria involved in the denitrifying activities. Here, we report the capacity of the denitrifying biofilm to sustain environmental changes, and the impact of these changes on the co-occurrence of H. nitrativorans and M. nitratireducenticrescens. Methods In a first set of assays, the original biofilm (OB) was cultivated in an artificial seawater (ASW) medium under anoxic conditions to colonize new carriers. The new formed biofilm was then subjected to short exposures (1–5 days) of a range of NaCl, methanol, nitrate (NO3−) and nitrite (NO2−) concentrations, and to different pHs and temperatures. In a second set of assays, the OB was cultivated in ASW medium for five weeks with (i) a range of NaCl concentrations, (ii) four combinations of NO3−/methanol concentrations and temperatures, (iii) NO2−, and (iv) under oxic conditions. Finally, the OB was cultivated for five weeks in the commercial Instant Ocean (IO) seawater. The growth of the biofilm and the dynamics of NO3− and NO2− were determined. The levels of M. nitratireducenticrescens and H. nitrativorans were measured by qPCR. Results In the first set of assays, the biofilm cultures had the capacity to sustain denitrifying activities in most of the tested conditions. Inhibition occurred when they were exposed to high pH (10) or to high methanol concentration (1.5%). In the second set of assays, the highest specific denitrification rates occurred with the biofilm cultures cultivated at 64.3 mM NO3− and 0.45% methanol, and at 30 °C. Poor biofilm development occurred with the biofilm cultures cultivated at 5% and 8% NaCl. In all biofilm cultures cultivated in ASW at 2.75% NaCl, H. nitrativorans strain NL23 decreased by three orders of magnitude in concentrations compared to that found in OB. This decrease coincided with the increase of the same magnitude of a subpopulation of M. nitratireducenticrescens (strain GP59 as representative). In the biofilm cultures cultivated at low NaCl concentrations (0% to 1.0%), persistence of H. nitrativorans strain NL23 was observed, with the gradual increase in concentrations of M. nitratireducenticrescens strain GP59. High levels of H. nitrativorans strain NL23 were found in the IO biofilm cultures. The concentrations of M. nitratireducenticrescens strain JAM1 were lower in most of the biofilms cultures than in OB. Conclusions These results demonstrate the plasticity of the marine methylotrophic denitrifying biofilm in adapting to different environmental changes. The NaCl concentration is a crucial factor in the dynamics of H. nitrativorans strain NL23, for which growth was impaired above 1% NaCl in the ASW-based biofilm cultures in favor of M. nitratireducenticrescens strain GP59.
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Spoering, Amy L., e Kim Lewis. "Biofilms and Planktonic Cells of Pseudomonas aeruginosa Have Similar Resistance to Killing by Antimicrobials". Journal of Bacteriology 183, n. 23 (1 dicembre 2001): 6746–51. http://dx.doi.org/10.1128/jb.183.23.6746-6751.2001.
Testo completoAbstract (sommario):
ABSTRACT Biofilms are considered to be highly resistant to antimicrobial agents. Strictly speaking, this is not the case—biofilms do not grow in the presence of antimicrobials any better than do planktonic cells. Biofilms are indeed highly resistant to killing by bactericidal antimicrobials, compared to logarithmic-phase planktonic cells, and therefore exhibit tolerance. It is assumed that biofilms are also significantly more tolerant than stationary-phase planktonic cells. A detailed comparative examination of tolerance of biofilms versus stationary- and logarithmic-phase planktonic cells with four different antimicrobial agents was performed in this study. Carbenicillin appeared to be completely ineffective against both stationary-phase cells and biofilms. Killing by this β-lactam antibiotic depends on rapid growth, and this result confirms the notion of slow-growing biofilms resembling the stationary state. Ofloxacin is a fluoroquinolone antibiotic that kills nongrowing cells, and biofilms and stationary-phase cells were comparably tolerant to this antibiotic. The majority of cells in both populations were eradicated at low levels of ofloxacin, leaving a fraction of essentially invulnerable persisters. The bulk of the population in both biofilm and stationary-phase cultures was tolerant to tobramycin. At very high tobramycin concentrations, a fraction of persister cells became apparent in stationary-phase culture. Stationary-phase cells were more tolerant to the biocide peracetic acid than were biofilms. In general, stationary-phase cells were somewhat more tolerant than biofilms in all of the cases examined. We concluded that, at least forPseudomonas aeruginosa, one of the model organisms for biofilm studies, the notion that biofilms have greater resistance than do planktonic cells is unwarranted. We further suggest that tolerance to antibiotics in stationary-phase or biofilm cultures is largely dependent on the presence of persister cells.
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HARGREAVES, D. G., A. PAJKOS, A. K. DEVA, K. VICKERY, S. L. FILAN e M. A. TONKIN. "The Role of Biofilm Formation in Percutaneous Kirschner-Wire Fixation of Radial Fractures". Journal of Hand Surgery 27, n. 4 (agosto 2002): 365–68. http://dx.doi.org/10.1054/jhsb.2002.0756.
Testo completoAbstract (sommario):
This study examines the formation of bacterial biofilms on percutaneous wires used for fracture fixation. Twelve control (clinically uninfected) wires and ten infected wires were collected and examined using broth culture and scanning electron microscopy. Three of the 12 control wires grew Staphylococcus spp. with very low bacterial counts in their percutaneous portions. In the clinically infected wires, six wires in four subjects had positive cultures in their percutaneous portions and four of these also had positive cultures in their deep portions with much higher bacterial counts than the controls. In two patients (four wires) treated with antibiotics, cultures were negative except for the percutaneous portion of one wire. Scanning electron microscopy did not reveal bacterial biofilm formation, but biological deposit without bacteria was noted on most wires. During the 6 weeks of fracture fixation, some bacterial colonization of wires occurred, but bacteria did not form biofilms which may increase bacterial resistance to systemic antibiotics, cause implant loosening and act as a source of late infection.
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Elkins, James G., Daniel J. Hassett, Philip S. Stewart, Herbert P. Schweizer e Timothy R. McDermott. "Protective Role of Catalase in Pseudomonas aeruginosa Biofilm Resistance to Hydrogen Peroxide". Applied and Environmental Microbiology 65, n. 10 (1 ottobre 1999): 4594–600. http://dx.doi.org/10.1128/aem.65.10.4594-4600.1999.
Testo completoAbstract (sommario):
ABSTRACT The role of the two known catalases in Pseudomonas aeruginosa in protecting planktonic and biofilm cells against hydrogen peroxide (H2O2) was investigated. Planktonic cultures and biofilms formed by the wild-type strain PAO1 and the katA and katB catalase mutants were compared for their susceptibility to H2O2. Over the course of 1 h, wild-type cell viability decreased steadily in planktonic cells exposed to a single dose of 50 mM H2O2, whereas biofilm cell viability remained at approximately 90% when cells were exposed to a flowing stream of 50 mM H2O2. The katB mutant, lacking the H2O2-inducible catalase KatB, was similar to the wild-type strain with respect to H2O2 resistance. The katA mutant possessed undetectable catalase activity. PlanktonickatA mutant cultures were hypersusceptible to a single dose of 50 mM H2O2, while biofilms displayed a 10-fold reduction in the number of culturable cells after a 1-h exposure to 50 mM H2O2. Catalase activity assays, activity stains in nondenaturing polyacrylamide gels, andlacZ reporter genes were used to characterize the oxidative stress responses of planktonic cultures and biofilms. Enzyme assays and catalase activity bands in nondenaturing polyacrylamide gels showed significant KatB catalase induction occurred in biofilms after a 20-min exposure to H2O2, suggesting that biofilms were capable of a rapid adaptive response to the oxidant. Reporter gene data obtained with a katB::lacZtranscriptional reporter strain confirmed katB induction and that the increase in total cellular catalase activity was attributable to KatB. Biofilms upregulated the reporter in the constant presence of 50 mM H2O2, while planktonic cells were overwhelmed by a single 50 mM dose and were unable to make detectable levels of β-galactosidase. The results of this study demonstrated the following: the constitutively expressed KatA catalase is important for resistance of planktonic and biofilm P. aeruginosa to H2O2, particularly at high H2O2 concentrations; KatB is induced in both planktonic and biofilm cells in response to H2O2 insult, but plays a relatively small role in biofilm resistance; and KatB is important to either planktonic cells or biofilm cells for acquired antioxidant resistance when initial levels of H2O2 are sublethal.
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Saginur, Raphael, Melissa StDenis, Wendy Ferris, Shawn D. Aaron, Francis Chan, Craig Lee e Karam Ramotar. "Multiple Combination Bactericidal Testing of Staphylococcal Biofilms from Implant-Associated Infections". Antimicrobial Agents and Chemotherapy 50, n. 1 (gennaio 2006): 55–61. http://dx.doi.org/10.1128/aac.50.1.55-61.2006.
Testo completoAbstract (sommario):
ABSTRACT Standardized susceptibility testing fails to predict in vivo resistance of device-related infections to antimicrobials. We assessed agents and combinations of antimicrobials against clinical isolates of Staphylococcus epidermidis and S. aureus (methicillin-resistant S. aureus and methicillin-sensitive S. aureus) retrieved from device-associated infections. Isolates were grown planktonically and as biofilms. Biofilm cultures of the organisms were found to be much more resistant to inhibitory and bactericidal effects of single and combination antibiotics than planktonic cultures (P < 0.001). Rifampin was the most common constituent of antibiotic combinations active against staphylococcal biofilms. Other frequently effective antimicrobials were vancomycin and fusidic acid. Susceptibility testing involving biofilm-associated bacteria suggests new options for combination antibiotic therapy.
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Zannier, Federico, Luciano Raúl Portero, Omar Federico Ordoñez, Luciano José Martinez, María Eugenia Farías e Virginia Helena Albarracin. "Polyextremophilic Bacteria from High Altitude Andean Lakes: Arsenic Resistance Profiles and Biofilm Production". BioMed Research International 2019 (21 febbraio 2019): 1–11. http://dx.doi.org/10.1155/2019/1231975.
Testo completoAbstract (sommario):
High levels of arsenic present in the High Altitude Andean Lakes (HAALs) ecosystems selected arsenic-resistant microbial communities which are of novel interest to study adaptations mechanisms potentially useful in bioremediation processes. We herein performed a detailed characterization of the arsenic tolerance profiles and the biofilm production of two HAAL polyextremophiles, Acinetobacter sp. Ver3 (Ver3) and Exiguobacterium sp. S17 (S17). Cellular adherence over glass and polypropylene surfaces were evaluated together with the effect of increasing doses and oxidative states of arsenic over the quality and quantity of their biofilm production. The arsenic tolerance outcomes showed that HAAL strains could tolerate higher arsenic concentrations than phylogenetic related strains belonging to the German collection of microorganisms and cell cultures (Deutsche Sammlung von Mikroorganismen und Zellkulturen, DSMZ), which suggest adaptations of HAAL strains to their original environment. On the other hand, the crystal violet method (CV) and SEM analysis showed that Ver3 and S17 were able to attach to solid surfaces and to form the biofilm. The quantification of biofilms production in 48 hours’ cultures through CV shows that Ver3 yielded higher production in the treatment without arsenic cultured on a glass support, while S17 yield higher biofilm production under intermediate arsenic concentration on glass supports. Polypropylene supports had negative effects on the biofilm production of Ver3 and S17. SEM analysis shows that the highest biofilm yields could be associated with a larger number of attached cells as well as the development of more complex 3D multicellular structures.
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Niemira, Brendan A., e Ethan B. Solomon. "Sensitivity of Planktonic and Biofilm-Associated Salmonella spp. to Ionizing Radiation". Applied and Environmental Microbiology 71, n. 5 (maggio 2005): 2732–36. http://dx.doi.org/10.1128/aem.71.5.2732-2736.2005.
Testo completoAbstract (sommario):
ABSTRACT Salmonella enterica forms biofilms that are relatively resistant to chemical sanitizing treatments. Ionizing radiation has been used to inactivate Salmonella on a variety of foods and contact surfaces, but the relative efficacy of the process against biofilm-associated cells versus free-living planktonic cells is not well documented. The radiation sensitivity of planktonic or biofilm-associated cells was determined for three food-borne-illness-associated isolates of Salmonella. Biofilms were formed on sterile glass slides in a coincubation apparatus, using inoculated tryptic soy broth, incubated at 37°C for 48 h. Resulting biofilms were 18 to 24 μm in height as determined by confocal scanning laser microscopy. The planktonic and biofilm cultures were gamma irradiated to doses of 0.0 (control), 0.5, 1.0, 1.5, 2.0 and 2.5 kGy. The D 10 value (the dose of radiation required to reduce a population by 1 log10, or 90%) was calculated for each isolate-culture based on surviving populations at each radiation dose. The D 10 values of S. enterica serovar Anatum were not significantly (P < 0.05) different for biofilm-associated (0.645 kGy) and planktonic (0.677 kGy) cells. In contrast, the biofilm-associated cells of S. enterica serovar Stanley were significantly more sensitive to ionizing radiation than the respective planktonic cells, with D 10 values of 0.531 and 0.591 kGy, respectively. D 10 values of S. enterica serovar Enteritidis were similarly reduced for biofilm-associated (0.436 kGy) versus planktonic (0.535 kGy) cells. The antimicrobial efficacy of ionizing radiation is therefore preserved or enhanced in treatment of biofilm-associated bacteria.
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Maggio, Francesca, Chiara Rossi, Clemencia Chaves-López, Annalisa Serio, Luca Valbonetti, Francesco Pomilio, Alessio Pio Chiavaroli e Antonello Paparella. "Interactions between L. monocytogenes and P. fluorescens in Dual-Species Biofilms under Simulated Dairy Processing Conditions". Foods 10, n. 1 (16 gennaio 2021): 176. http://dx.doi.org/10.3390/foods10010176.
Testo completoAbstract (sommario):
In dairy processing environments, many bacterial species adhere and form biofilms on surfaces and equipment, leading to foodborne illness and food spoilage. Among them, Listeria monocytogenes and Pseudomonas spp. could be present in mixed-species biofilms. This study aimed to evaluate the interactions between L. monocytogenes and P. fluorescens in biofilms simulating dairy processing conditions, as well as the capability of P. fluorescens in co-culture to produce the blue pigment in a Ricotta-based model system. The biofilm-forming capability of single- and mixed-cultures was evaluated on polystyrene (PS) and stainless steel (SS) surfaces at 12 °C for 168 h. The biofilm biomass was measured, the planktonic and sessile cells and the carbohydrates in biofilms were quantified. The biofilms were also observed through Confocal Laser Scanning Microscopy analysis. Results showed that only P. fluorescens was able to form biofilms on PS. Moreover, in dual-species biofilms at the end of the incubation time (168 h at 12 °C), a lower biomass compared to P. fluorescens mono-species was observed on PS. On SS, the biofilm cell population of L. monocytogenes was higher in the dual-species than in mono-species, particularly after 48 h. Carbohydrates quantity in the dual-species system was higher than in mono-species and was revealed also at 168 h. The production of blue pigment by P. fluorescens was revealed both in single- and co-culture after 72 h of incubation (12 °C). This work highlights the interactions between the two species, under the experimental conditions studied in the present research, which can influence biofilm formation (biomass and sessile cells) but not the capability of P. fluorescens to produce blue pigment.
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Valieva, R. I., S. A. Lisovskaya, K. A. Mayanskaya, D. V. Samigullin e G. Sh Isaeva. "Features of antifungal therapy during long-lasting infectious process: a clinical case of fungal keratitis and profile of antifungal sensitivity based on assessing biofilm formation". Russian Journal of Infection and Immunity 11, n. 4 (20 settembre 2021): 789–97. http://dx.doi.org/10.15789/2220-7619-foa-1495.
Testo completoAbstract (sommario):
Among infectious diseases, opportunistic mycoses hold a special place. There has been accumulating a lot of evidence regarding the clinical and epidemiological aspects of infection caused by Fusarium spp., which global incidence rate among microbial keratitis ranges from 2 to 40% depending on the geographical location of the country. Colonizing mucous membranes, fungi can exist not only in the form of plankton, but form biofilms after surface attachment, which leads to elevated resistance to multiple antifungal agents. Here we describe a clinical case of fungal keratitis due to Fusarium solani by determining profile of the antifungal sensitivity for isolated fungal strains, by taking into account their potential for biofilm formation. We used an F. solani culture isolated from the patient as well as F. solani test culture obtained from the Russian National Collection of Microorganisms. While determining the sensitivity of fungal planktonic cultures to antifungal agents from the azole group (fluconazole, voriconazole), amphotericin B and terbinafine, it was revealed that antimycotics amphotericin B and voriconazole exerted a marked antifungal activity against clinical isolate, whereas the plankton F. solani test culture was more sensitive to all groups of antifungal agents. Due to a long-lasting progressive course of the infectious process and the high biofilm-forming ability of the clinical strain F. solani, the activity of antifungal agents on biofilm cells was modeled and examined in vitro. It was shown that regarding to the fungal biofilms, value of the minimally inhibitory concentration exceeded those for planktonic cultures by 100-fold. The mechanisms of action for antifungal agents on vital parameters of fungal cell structures were analyzed by using confocal laser scanning microscopy after staining samples with propidium iodide and acridine orange for 15 min to detect changes between intact and damaged cell surface. It was found that within the biofilm fungal cells preserved viability even after exposure to high concentrations of antifungals. In addition, despite the fungicidal drug activity at substantial concentrations acting on the biofilm cell membrane, the cell nuclei remained viable. Owing to the presence ot the mechanism of resistance in mycelial fungi shown in the study, it is necessary to take into account and investigate characteristics of biofilms in terms of drug sensitivity that will allow to optimize a choice of antimicrobial therapy.
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Hunt, Stephen M., Erin M. Werner, Baochuan Huang, Martin A. Hamilton e Philip S. Stewart. "Hypothesis for the Role of Nutrient Starvation in Biofilm Detachment". Applied and Environmental Microbiology 70, n. 12 (dicembre 2004): 7418–25. http://dx.doi.org/10.1128/aem.70.12.7418-7425.2004.
Testo completoAbstract (sommario):
ABSTRACT A combination of experimental and theoretical approaches was used to investigate the role of nutrient starvation as a potential trigger for biofilm detachment. Experimental observations of detachment in a variety of biofilm systems were made with pure cultures of Pseudomonas aeruginosa. These observations indicated that biofilms grown under continuous-flow conditions detached after flow was stopped, that hollow cell clusters were sometimes observed in biofilms grown in flow cells, and that lysed cells were apparent in the internal strata of colony biofilms. When biofilms were nutrient starved under continuous-flow conditions, detachment still occurred, suggesting that starvation and not the accumulation of a metabolic product was responsible for triggering detachment in this particular system. A cellular automata computer model of biofilm dynamics was used to explore the starvation-dependent detachment mechanism. The model predicted biofilm structures and dynamics that were qualitatively similar to those observed experimentally. The predicted features included centrally located voids appearing in sufficiently large cell clusters, gradients in growth rate within these clusters, and the release of most of the biofilm with simulated stopped-flow conditions. The model was also able to predict biofilm sloughing resulting solely from this detachment mechanism. These results support the conjecture that nutrient starvation is an environmental cue for the release of microbes from a biofilm.
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Gerner, Erik, Sofia Almqvist, Peter Thomsen, Maria Werthén e Margarita Trobos. "Sodium Salicylate Influences the Pseudomonas aeruginosa Biofilm Structure and Susceptibility Towards Silver". International Journal of Molecular Sciences 22, n. 3 (21 gennaio 2021): 1060. http://dx.doi.org/10.3390/ijms22031060.
Testo completoAbstract (sommario):
Hard-to-heal wounds are typically infected with biofilm-producing microorganisms, such as Pseudomonas aeruginosa, which strongly contribute to delayed healing. Due to the global challenge of antimicrobial resistance, alternative treatment strategies are needed. Here, we investigated whether inhibition of quorum sensing (QS) by sodium salicylate in different P. aeruginosa strains (QS-competent, QS-mutant, and chronic wound strains) influences biofilm formation and tolerance to silver. Biofilm formation was evaluated in simulated serum-containing wound fluid in the presence or absence of sodium salicylate (NaSa). Biofilms were established using a 3D collagen-based biofilm model, collagen coated glass, and the Calgary biofilm device. Furthermore, the susceptibility of 48-h-old biofilms formed by laboratory and clinical strains in the presence or absence of NaSa towards silver was evaluated by assessing cell viability. Biofilms formed in the presence of NaSa were more susceptible to silver and contained reduced levels of virulence factors associated with biofilm development than those formed in the absence of NaSa. Biofilm aggregates formed by the wild-type but not the QS mutant strain, were smaller and less heterogenous in size when grown in cultures with NaSa compared to control. These data suggest that NaSa, via a reduction of cell aggregation in biofilms, allows the antiseptic to become more readily available to cells.
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Cushion, Melanie T., e Margaret S. Collins. "Susceptibility of Pneumocystis to Echinocandins in Suspension and Biofilm Cultures". Antimicrobial Agents and Chemotherapy 55, n. 10 (25 luglio 2011): 4513–18. http://dx.doi.org/10.1128/aac.00017-11.
Testo completoAbstract (sommario):
ABSTRACTThe targeted inhibition of cyst but not trophic development by anidulafungin, caspofungin, and micafungin onPneumocystis murinaandPneumocystis cariniiin rodent models ofPneumocystis cariniipneumonia (PCP) was recently reported by us (M. T. Cushion et al., PLoS One 5:e8524, 2010). To better understand the effects of echinocandins onP. carinii, the same three compounds were evaluated in standard suspension and biofilm cultures supplemented with various concentrations of sera using the measurement of ATP as the indicator. In suspension cultures with 1 and 5% serum, anidulafungin was the most active compound but 10 and 20% serum abrogated the efficacy of all three echinocandins. Established biofilm cultures that included both the nonadherent and adherent phases were more resistant to micafungin than caspofungin regardless of serum concentration, while anidulafungin had significant activity at 1 and 5% serum concentrations. Nascent biofilms were mostly affected by anidulafungin in 1 and 5% serum, but none of the compounds showed significant activity in 20% serum. We show for the first time that (i) echinocandins differ in their abilities to deplete the ATP ofPneumocystisin biofilms and in suspension cultures, (ii) this variability mostly reflected the reported efficacies in animal models of infection, and (iii) high serum levels decreased the anti-Pneumocystisactivities of the echinocandins in bothin vitrosystems.
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Hathroubi, Skander, Francis Beaudry, Chantale Provost, Léa Martelet, Mariela Segura, Carl A. Gagnon e Mario Jacques. "Impact ofActinobacillus pleuropneumoniaebiofilm mode of growth on the lipid A structures and stimulation of immune cells". Innate Immunity 22, n. 5 (25 maggio 2016): 353–62. http://dx.doi.org/10.1177/1753425916649676.
Testo completoAbstract (sommario):
Actinobacillus pleuropneumoniae (APP), the etiologic agent of porcine pleuropneumonia, forms biofilms on biotic and abiotic surfaces. APP biofilms confers resistance to antibiotics. To our knowledge, no studies have examined the role of APP biofilm in immune evasion and infection persistence. This study was undertaken to (i) investigate biofilm-associated LPS modifications occurring during the switch to biofilm mode of growth; and (ii) characterize pro-inflammatory cytokines expression in porcine pulmonary alveolar macrophages (PAMs) and proliferation in porcine PBMCs challenged with planktonic or biofilm APP cells. Extracted lipid A samples from biofilm and planktonic cultures were analyzed by HPLC high-resolution, accurate mass spectrometry. Biofilm cells displayed significant changes in lipid A profiles when compared with their planktonic counterparts. Furthermore, in vitro experiments were conducted to examine the inflammatory response of PAMs exposed to UV-inactivated APP grown in biofilm or in suspension. Relative mRNA expression of pro-inflammatory genes IL1, IL6, IL8 and MCP1 decreased in PAMs when exposed to biofilm cells compared to planktonic cells. Additionally, the biofilm state reduced PBMCs proliferation. Taken together, APP biofilm cells show a weaker ability to stimulate innate immune cells, which could be due, in part, to lipid A structure modifications.
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Wijesinghe, Gayan, Ayomi Dilhari, Buddhika Gayani, Nilwala Kottegoda, Lakshman Samaranayake e Manjula Weerasekera. "Influence of Laboratory Culture Media on in vitro Growth, Adhesion, and Biofilm Formation of Pseudomonas aeruginosa and Staphylococcus aureus". Medical Principles and Practice 28, n. 1 (23 ottobre 2018): 28–35. http://dx.doi.org/10.1159/000494757.
Testo completoAbstract (sommario):
Objective: Pseudomonas aeruginosa and Staphylococcus aureus dual-species biofilm infections are notoriously difficult to manage. This study aimed at investigating the influence of four different culture media on the planktonic growth, adhesion, and biofilm formation of P. aeruginosa and S. aureus. Materials and Methods: We monitored four different culture media including Nutrient Broth, Brain Heart Infusion (BHI) broth, Luria-Bertani broth, and RPMI 1640 medium on the planktonic growth, adhesion, and biofilm formation of P. aeruginosa (ATCC 27853) and S. aureus (ATCC 25923) using MTT assay and scanning electron microscopy (SEM). Results: The most robust growth of the mono- and dual-species cultures was noted in BHI broth. On the contrary, RPMI 1640 medium promoted maximal initial adhesion of both the mono- and dual-species, but BHI broth fostered the maximal biofilm growth. SEM images showed profuse extracellular polysaccharide production in biofilms, particularly in coculture, in BHI medium. Conclusion: Our data demonstrate that BHI broth, relative to the other tested media, is the most conducive for in vitro evaluation of biofilm and planktonic growth kinetics of these two pathogens, both in mono- and coculture.
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Ghani, M., e J. S. Soothill. "Ceftazidime, gentamicin, and rifampicin, in combination, kill biofilms of mucoidPseudomonas aeruginosa". Canadian Journal of Microbiology 43, n. 11 (1 novembre 1997): 999–1004. http://dx.doi.org/10.1139/m97-144.
Testo completoAbstract (sommario):
In continuous flow biofilm cultures in medium resembling cystic fibrosis bronchial secretions, Pseudomonas aeruginosa was not eradicated from biofilms by 1 week of treatment with high concentrations of ceftazidime and gentamicin, to which the strains were sensitive on conventional testing. The addition of rifampicin, which has little activity against the strains as measured by the minimum inhibitory concentration, led to the apparent elimination of the bacteria from the biofilms. The effect was not strain specific.Key words: Pseudomonas aeruginosa, biofilm, rifampicin.
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Kononenko, A. B., D. A. Bannikova, I. B. Pavlova, S. V. Britova e E. P. Savinova. "FORMATION OF BIOLOGICAL FILMS OF MICROORGANISMS ON VARIOUS SURFACES OF THE ENVIRONMENT". Problems of Veterinary Sanitation, Hygiene and Ecology 1, n. 3 (2020): 333–40. http://dx.doi.org/10.36871/vet.san.hyg.ecol.202003008.
Testo completoAbstract (sommario):
The article presents material on the results of experimental studies on the formation of biofilms by microorganisms of individual taxonomic groups on various surfaces of objects of the environment. The time and degree of biofilm formation, as well as the dependence on the type of surface and bacteria, were established. The cultures of the genera Salmonella, E. coli, Yersinia, Proteus, Pseudomonas and Staphylococcus were used in the work. To study the formation of biofilms, 24-hour cultures of S-form microorganisms grown on solid or in liquid nutrient media were used. Test objects were stained with 0,1% crystalline violet solution for 15 minutes, unbound dye was washed off with physiological saline or distilled water. Test objects were placed on filter paper and dried. Then 200 microliters of 96% ethanol were added to extract the paint from the film and the optical density was measured on a KFK-3KM spectrophotometer at wavelength of 590 nm. It was found that conditionally pathogenic and pathogenic microorganisms form a biofilm on both smooth and rough abiotic surfaces within 48 hours. Moreover, the intensity of biofilm formation on rough surfaces is higher than on smooth ones by 15...30%. Among the studied microorganisms, the most intensive development of biofilm was observed in Ps. cultures. aeruginosa and Pr. vulgaris. Biofilms pose a potential danger of contamination of feed, food raw materials and, most importantly, food products, since they can exist for a long time on a wide variety of surfaces of production facilities of the respective enterprises.
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Geoffroy, Valérie, Geneviève Payette, Florian Mauffrey, Livie Lestin, Philippe Constant e Richard Villemur. "Strain-level genetic diversity ofMethylophaga nitratireducenticrescensconfers plasticity to denitrification capacity in a methylotrophic marine denitrifying biofilm". PeerJ 6 (23 aprile 2018): e4679. http://dx.doi.org/10.7717/peerj.4679.
Testo completoAbstract (sommario):
BackgroundThe biofilm of a methanol-fed, fluidized denitrification system treating a marine effluent is composed of multi-species microorganisms, among whichHyphomicrobium nitrativoransNL23 andMethylophaga nitratireducenticrescensJAM1 are the principal bacteria involved in the denitrifying activities. Strain NL23 can carry complete nitrate (NO${}_{3}^{-}$) reduction to N2, whereas strain JAM1 can perform 3 out of the 4 reduction steps. A small proportion of other denitrifiers exists in the biofilm, suggesting the potential plasticity of the biofilm in adapting to environmental changes. Here, we report the acclimation of the denitrifying biofilm from continuous operating mode to batch operating mode, and the isolation and characterization from the acclimated biofilm of a new denitrifying bacterial strain, named GP59.MethodsThe denitrifying biofilm was batch-cultured under anoxic conditions. The acclimated biofilm was plated onMethylophagaspecific medium to isolate denitrifyingMethylophagaisolates. Planktonic cultures of strains GP59 and JAM1 were performed, and the growth and the dynamics of NO${}_{3}^{-}$, nitrite (NO${}_{2}^{-}$) and N2O were determined. The genomes of strains GP59 and JAM1 were sequenced and compared. The transcriptomes of strains GP59 and JAM1 were derived from anoxic cultures.ResultsDuring batch cultures of the biofilm, we observed the disappearance ofH. nitrativoransNL23 without affecting the denitrification performance. From the acclimated biofilm, we isolated strain GP59 that can perform, likeH. nitrativoransNL23, the complete denitrification pathway. The GP59 cell concentration in the acclimated biofilm was 2–3 orders of magnitude higher thanM. nitratireducenticrescensJAM1 andH. nitrativoransNL23. Genome analyses revealed that strain GP59 belongs to the speciesM. nitratireducenticrescens. The GP59 genome shares more than 85% of its coding sequences with those of strain JAM1. Based on transcriptomic analyses of anoxic cultures, most of these common genes in strain GP59 were expressed at similar level than their counterparts in strain JAM1. In contrast to strain JAM1, strain GP59 cannot reduce NO${}_{3}^{-}$ under oxic culture conditions, and has a 24-h lag time before growth and NO${}_{3}^{-}$ reduction start to occur in anoxic cultures, suggesting that both strains regulate differently the expression of their denitrification genes. Strain GP59 has the ability to reduce NO${}_{2}^{-}$ as it carries a gene encoding a NirK-type NO${}_{2}^{-}$ reductase. Based on the CRISPR sequences, strain GP59 did not emerge from strain JAM1 during the biofilm batch cultures but rather was present in the original biofilm and was enriched during this process.DiscussionThese results reinforce the unique trait of the speciesM. nitratireducenticrescensamong theMethylophagagenus as facultative anaerobic bacterium. These findings also showed the plasticity of denitrifying population of the biofilm in adapting to anoxic marine environments of the bioreactor.