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1
Kesel, Sara, Stefan Grumbein, Ina Gümperlein, Marwa Tallawi, Anna-Kristina Marel, Oliver Lieleg, and Madeleine Opitz. "Direct Comparison of Physical Properties of Bacillus subtilis NCIB 3610 and B-1 Biofilms." Applied and Environmental Microbiology 82, no. 8 (February 12, 2016): 2424–32. http://dx.doi.org/10.1128/aem.03957-15.
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ABSTRACTMany bacteria form surface-attached communities known as biofilms. Due to the extreme resistance of these bacterial biofilms to antibiotics and mechanical stresses, biofilms are of growing interest not only in microbiology but also in medicine and industry. Previous studies have determined the extracellular polymeric substances present in the matrix of biofilms formed byBacillus subtilisNCIB 3610. However, studies on the physical properties of biofilms formed by this strain are just emerging. In particular, quantitative data on the contributions of biofilm matrix biopolymers to these physical properties are lacking. Here, we quantitatively investigated three physical properties ofB. subtilisNCIB 3610 biofilms: the surface roughness and stiffness and the bulk viscoelasticity of these biofilms. We show how specific biomolecules constituting the biofilm matrix formed by this strain contribute to those biofilm properties. In particular, we demonstrate that the surface roughness and surface elasticity of 1-day-old NCIB 3610 biofilms are strongly affected by the surface layer protein BslA. For a second strain,B. subtilisB-1, which forms biofilms containing mainly γ-polyglutamate, we found significantly different physical biofilm properties that are also differently affected by the commonly used antibacterial agent ethanol. We show that B-1 biofilms are protected from ethanol-induced changes in the biofilm's stiffness and that this protective effect can be transferred to NCIB 3610 biofilms by the sole addition of γ-polyglutamate to growing NCIB 3610 biofilms. Together, our results demonstrate the importance of specific biofilm matrix components for the distinct physical properties ofB. subtilisbiofilms.
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Ferris, Ryan A., Patrick M. McCue, Grace I. Borlee, Kristen D. Loncar, Margo L. Hennet, and Bradley R. Borlee. "In VitroEfficacy of Nonantibiotic Treatments on Biofilm Disruption of Gram-Negative Pathogens and anIn VivoModel of Infectious Endometritis Utilizing Isolates from the Equine Uterus." Journal of Clinical Microbiology 54, no. 3 (December 30, 2015): 631–39. http://dx.doi.org/10.1128/jcm.02861-15.
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In this study, we evaluated the ability of the equine clinical treatmentsN-acetylcysteine, EDTA, and hydrogen peroxide to disruptin vitrobiofilms and kill equine reproductive pathogens (Escherichia coli,Pseudomonas aeruginosa, orKlebsiella pneumoniae) isolated from clinical cases.N-acetylcysteine (3.3%) decreased biofilm biomass and killed bacteria within the biofilms ofE. coliisolates. The CFU of recoverableP. aeruginosaandK. pneumoniaeisolates were decreased, but the biofilm biomass was unchanged. Exposure to hydrogen peroxide (1%) decreased the biofilm biomass and reduced the CFU ofE. coliisolates,K. pneumoniaeisolates were observed to have a reduction in CFU, and minimal effects were observed forP. aeruginosaisolates. Chelating agents (EDTA formulations) reducedE. coliCFU but were ineffective at disrupting preformed biofilms or decreasing the CFU ofP. aeruginosaandK. pneumoniaewithin a biofilm. No single nonantibiotic treatment commonly used in equine veterinary practice was able to reduce the CFU and biofilm biomass of all three Gram-negative species of bacteria evaluated. Anin vivoequine model of infectious endometritis was also developed to monitor biofilm formation, utilizing bioluminescence imaging with equineP. aeruginosaisolates from this study. Following infection, the endometrial surface contained focal areas of bacterial growth encased in a strongly adherent “biofilm-like” matrix, suggesting that biofilms are present during clinical cases of infectious equine endometritis. Our results indicate that Gram-negative bacteria isolated from the equine uterus are capable of producing a biofilmin vitro, andP. aeruginosais capable of producing biofilm-like materialin vivo.
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Bhatta, Mahesh Prakash, Asmita Sapkota, Pushpa Subedi, Sunita Baniya Chhetri, Dhaka Raj Pant, Mukund Joshi, Santosh Pandit, and Dipendra Raj Pandeya. "Biofilm Formation by Uropathogens and Their Susceptibility Towards Antimicrobial Therapy." Medical Journal of Shree Birendra Hospital 18, no. 1 (February 26, 2019): 13–22. http://dx.doi.org/10.3126/mjsbh.v18i1.20189.
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Introduction: Urinary tract infection (UTI) is the most common health care associated infection caused by various pathogenic bacteria. Biofilms are communities of bacteria that are held together by exopolymeric substances that protect against the antimicrobial therapy and other environmental assaults. The aim of this study was to estimate the prevalence of biofilm forming bacteria in Nepalese population and to study the emergence of antimicrobial resistance among biofilm producing bacteria in comparison to non-biofilm producing bacteria.
Methods: A total of 785 clean-caught-mid-stream urine samples were collected. After isolation and identification of uropathogens, they were further processed for detection of biofilm formation by two methods (Congo Red Agar method and Tissue Culture Plate method) as well as for antibiotic sensitivity test.
Results: Out of total collected samples, 12.74% were found to be associated with UTI, among them 67% were Escherichia coli, 10% were Klebsiella spp, 7% were Pseudomonas spp, 6% were Staphyloccous aureus, 4% were Enterobacter spp, 3% were Proteus spp, 2% were Citrobacter spp and remaining 1% was Staphylococcus saprophyticus. Among isolated organisms, the ratio of bioflim positive organism to bioflim negative organism was found to be 9:11. Nitrofurantoin, Tobramycin, Chloramphenicol, Amikacin and Imipenem were found to be significantly more sensitive in biofilm negative bacteria as compared to biofilm positive bacteria with p values of 0.000, 0.001, 0.000, 0.000 and 0.001.
Conclusions: The prevalence rate of multidrug resistance in bacterial uropathogens was higher in biofilm producers as compared to non-biofilm producers. Biofilm forming characteristic of bacteria make them more resistant to antibiotics.
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Conwell, Michael, James S. G. Dooley, and Patrick J. Naughton. "A Novel Biofilm Model System to Visualise Conjugal Transfer of Vancomycin Resistance by Environmental Enterococci." Microorganisms 9, no. 4 (April 9, 2021): 789. http://dx.doi.org/10.3390/microorganisms9040789.
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Enterococci and biofilm-associated infections are a growing problem worldwide, given the rise in antibiotic resistance in environmental and clinical settings. The increasing incidence of antibiotic resistance and its propagation potential within enterococcal biofilm is a concern. This requires a deeper understanding of how enterococcal biofilm develops, and how antibiotic resistance transfer takes place in these biofilms. Enterococcal biofilm assays, incorporating the study of antibiotic resistance transfer, require a system which can accommodate non-destructive, real-time experimentation. We adapted a Gene Frame® combined with fluorescence microscopy as a novel non-destructive platform to study the conjugal transfer of vancomycin resistance in an established enterococcal biofilm.A multi-purpose fluorescent in situ hybridisation (FISH) probe, in a novel application, allowed the identification of low copy number mobile elements in the biofilm. Furthermore, a Hoechst stain and ENU 1470 FISH probe identified Enterococcus faecium transconjugants by excluding Enterococcus faecalis MF06036 donors. Biofilm created with a rifampicin resistant E. faecalis (MW01105Rif) recipient had a transfer efficiency of 2.01 × 10−3; double that of the biofilm primarily created by the donor (E. faecalis MF06036). Conjugation in the mixed enterococcal biofilm was triple the efficiency of donor biofilm. Double antibiotic treatment plus lysozyme combined with live/dead imaging provided fluorescent micrographs identifying de novo enterococcal vancomycin resistant transconjugants inside the biofilm. This is a model system for the further study of antibiotic resistance transfer events in enterococci. Biofilms promote the survival of enterococci and reduce the effectiveness of drug treatment in clinical settings, hence giving enterococci an advantage. Enterococci growing in biofilms exchange traits by means of horizontal gene transfer, but currently available models make study difficult. This work goes some way to providing a non-destructive, molecular imaging-based model system for the detection of antibiotic resistance gene transfer in enterococci.
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Lesmana, Muhamad Arfan, Dahliatul Qosimah, and Sri Murwani. "Detection of Staphylococcus aureus Biofilm from Subclinical Mastitis Milk." Veterinary Biomedical and Clinical Journal 1, no. 1 (January 1, 2019): 19–25. http://dx.doi.org/10.21776/ub.vetbioclinj.2019.001.01.3.
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One of S.aureus's virulence factors is biofilm formation. When biofilms are formed, the bacteria will undergo phenotypic changes that require higher concentrations of antibiotics to inhibit proliferation. Phenotypic changes will lead to increase the production of extracellular matrix and multilayered colonies as well as decrease of metabolic rates, multiplication and polymicrobial colonization resulting in recurrent infection in the host and difficulty being treated with antibiotics due to resistance. The aim of this research was to know the formation of bacterial biofim by slime and quantitative by microplate titer method. The research method was qualitative descriptive using 27 samples of Staphylococcus aureus with characterized from mastitis infected milk. The bacteria were grown on CRA (Congo Red Agar) media to observe the slime biofilm through bacteria black colony followed by MicrotiterPlate method with 570nm wave lenght. The results showed that 27 samples of Staphylococcus aureus which positive to form slime biofilm were 10 samples and continued to microtiter plate showed 3 positive samples of biofilm. The conclusions of this study, Staphylococcus aureus in subclinical mastitis milk samples were positive to form biofilms.
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van Loosdrecht, M. C. M., D. Eikelboom, A. Gjaltema, A. Mulder, L. Tijhuis, and J. J. Heijnen. "Biofilm structures." Water Science and Technology 32, no. 8 (October 1, 1995): 35–43. http://dx.doi.org/10.2166/wst.1995.0258.
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The influences of reactor conditions (substrate loading rate and shear) and microbial characteristics (yield and growth rate) on the structure of biofilms is discussed. Based on research on the formation of biofilms in Biofilm Airlift Suspension (BAS) reactors a hypothesis is postulated that the ratio between biofilm surface loading and shear rate determines the biofilm structure. When shear forces are relatively high only a patchy biofilm will develop, whereas at low shear rates the biofilm becomes highly heterogeneous with many pores and protuberances. In case of a right balance smooth and stable biofilms can be obtained. A hypothesis for the evolution of biofilm structures as a function of process conditions is formulated.
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Wang, Xiaoling, Mudong Hao, and Guoqing Wang. "Numerical simulation of wrinkle morphology formation and the evolution of different Bacillus subtilis biofilms." Water Science and Technology 73, no. 3 (October 10, 2015): 527–34. http://dx.doi.org/10.2166/wst.2015.486.
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Wrinkle morphology is a distinctive phenomenon observed in mature biofilms that are produced by a great number of bacteria. The wrinkle pattern depends on the mechanical properties of the agar substrate and the biofilm itself, governed by the extracellular matrix (ECM). Here we study the macroscopic structures and the evolution of Bacillus subtilis biofilm wrinkles using the commercial finite element software ABAQUS. A mechanical model and simulation are set up to analyze and evaluate bacteria biofilm's wrinkle characteristics. We uncover the wrinkle formation mechanism and enumerate the quantitative relationship between wrinkle structure and mechanical properties of biofilm and its substrate. Our work can be used to modify the wrinkle pattern and control the biofilm size.
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Lewandowski, Z., H. Beyenal, and D. Stookey. "Reproducibility of biofilm processes and the meaning of steady state in biofilm reactors." Water Science and Technology 49, no. 11-12 (June 1, 2004): 359–64. http://dx.doi.org/10.2166/wst.2004.0880.
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The need for reproducing biofilm processes is undisputable - the quality of biofilm research depends on this reproducibility. However, as many biofilm researchers know, long-term biofilm processes are notoriously difficult to reproduce. To avoid problems related to biofilm reproducibility two strategies are used: (1) to study very young biofilms that have accumulated for a few hours to a few days only, and (2) to run biofilm experiments only once. The first approach trades reproducibility for relevance because natural biofilms are usually older, often much older than a few days. This approach can be applied to answer questions relevant to initial events of biofilm formation but not questions relevant to long-term biofilm accumulation. The second approach conceals the problem of biofilm reproducibility. To assure reproducibility of biofilm processes, we methodically followed a procedure for growing biofilms in terms of microbial makeup, media composition, temperature, surface preparation, etc. Despite all this effort the reproducibility of our results for long term growth is unimpressive. Consequently, the question had to be asked: Are biofilm processes reproducible? The experiments described in this paper address this question. Biofilms grown in two identical and identically operated biofilm reactors had comparable structure only until the first sloughing event. After that, biofilms had different patterns of accumulation.
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Hengzhuang, Wang, Hong Wu, Oana Ciofu, Zhijun Song, and Niels Høiby. "In VivoPharmacokinetics/Pharmacodynamics of Colistin and Imipenem in Pseudomonas aeruginosa Biofilm Infection." Antimicrobial Agents and Chemotherapy 56, no. 5 (February 21, 2012): 2683–90. http://dx.doi.org/10.1128/aac.06486-11.
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ABSTRACTManyPseudomonas aeruginosaisolates from the airways of patients with cystic fibrosis (CF) are sensitive to antibiotics in susceptibility testing, but eradication of the infection is difficult. The main reason is the biofilm formation in the airways of patients with CF. The pharmacokinetics (PKs) and pharmacodynamics (PDs) of antimicrobials can reliably be used to predict whether antimicrobial regimens will achieve the maximum bactericidal effect against infections. Unfortunately, however, most PK/PD studies of antimicrobials have been done on planktonic cells and very few PK/PD studies have been done on biofilms, partly due to the lack of suitable modelsin vivo. In the present study, a biofilm lung infection model was developed to provide an objective and quantitative evaluation of the PK/PD profile of antimicrobials. Killing curves were set up to detect the antimicrobial kinetics on planktonic and biofilmP. aeruginosacellsin vivo. Colistin showed concentration-dependent killing, while imipenem showed time-dependent killing on both planktonic and biofilmP. aeruginosacellsin vivo. The parameter best correlated to the elimination of bacteria in lung by colistin was the area under the curve (AUC) versus MIC (AUC/MIC) for planktonic cells or the AUC versus minimal biofilm inhibitory concentration (MBIC; AUC/MBIC) for biofilm cells. The best-correlated parameter for imipenem was the time that the drug concentration was above the MIC for planktonic cells (TMIC) or time that the drug concentration was above the MBIC (TMBIC) for biofilm cells. However, the AUC/MIC of imipenem showed a better correlation with the efficacy of imipenem for biofilm infections (R2= 0.89) than planktonic cell infections (R2= 0.38). The postantibiotic effect (PAE) of colistin and imipenem was shorter in biofilm infections than planktonic cell infections in this model.
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Silva, Vanessa, Luciana Almeida, Vânia Gaio, Nuno Cerca, Vera Manageiro, Manuela Caniça, José L. Capelo, Gilberto Igrejas, and Patrícia Poeta. "Biofilm Formation of Multidrug-Resistant MRSA Strains Isolated from Different Types of Human Infections." Pathogens 10, no. 8 (July 30, 2021): 970. http://dx.doi.org/10.3390/pathogens10080970.
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Methicillin-resistant Staphylococcus aureus (MRSA) is one of the main pathogens causing chronic infections, mainly due to its capacity to form biofilms. However, the mechanisms underlying the biofilm formation of MRSA strains from different types of human infections are not fully understood. MRSA strains isolated from distinct human infections were characterized aiming to determine their biofilm-forming capacity, the biofilm resistance to conventional antibiotics and the prevalence of biofilm-related genes, including, icaA, icaB, icaC, icaD, fnbA, fnbB, clfA, clfB, cna, eno, ebpS, fib and bbp. Eighty-three clinical MRSA strains recovered from bacteremia episodes, osteomyelitis and diabetic foot ulcers were used. The biofilm-forming capacity was evaluated by the microtiter biofilm assay and the biofilm structure was analyzed via confocal scanning laser microscopy. The antimicrobial susceptibility of 24-h-old biofilms was assessed against three antibiotics and the biomass reduction was measured. The metabolic activity of biofilms was evaluated by the XTT assay. The presence of biofilm-related genes was investigated by whole-genome sequencing and by PCR. Despite different intensities, all strains showed the capacity to form biofilms. Most strains had also a large number of biofilm-related genes. However, strains isolated from osteomyelitis showed a lower capacity to form biofilms and also a lower prevalence of biofilm-associated genes. There was a significant reduction in the biofilm biomass of some strains tested against antibiotics. Our results provide important information on the biofilm-forming capacity of clinical MRSA strains, which may be essential to understand the influence of different types of infections on biofilm production and chronic infections.
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Norsker, Niels H., Per H. Nielsen, and Thorkild Hvitved-Jacobsen. "Influence of oxygen on biofilm growth and potential sulfate reduction in gravity sewer biofilm." Water Science and Technology 31, no. 7 (April 1, 1995): 159–67. http://dx.doi.org/10.2166/wst.1995.0223.
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Under conditions of high organic surface load and high hydraulic shear the influence of bulk water dissolved oxygen (DO) concentration on biofilm oxygen consumption, biofilm growth and sulfate reduction in biofilms was investigated using both domestic wastewater and synthetic glucose - yeast extract medium. The biofilm thickness apparently did not approach a steady-state value; instead biofilm thickness increased linearly until the entire biofilm eventually sloughed. Potential activity of sulfate-reducing bacteria was highest when the biofilms were grown at low DO levels in bulk water. Potential sulfide production measured per biofilm volume remained fairly constant during the growth of the biofilms. Only at oxygen levels close to 0 ppm was sulfide production into bulk water under aerobic conditions evident; at higher oxygen levels, complete reoxidation of sulfide occurred within the biofilm. For biofilms growing at bulk oxygen conditions below 1 ppm, the sulfate reduction (and thus sulfide production) was of significance for the processes in the biofilm system in terms of oxygen consumption and COD removal.
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Pizarro, G. E., C. Garcia, R. Moreno, and M. E. Sepulveda. "Two-dimensional cellular automaton model for mixed-culture biofilm." Water Science and Technology 49, no. 11-12 (June 1, 2004): 193–98. http://dx.doi.org/10.2166/wst.2004.0839.
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Structural and microbial heterogeneity occurs in almost any type of biofilm system. General approaches for the design of biofilm systems consider biofilms as homogeneous and of constant thickness. In order to improve the design of biofilms systems, models need to incorporate structural heterogeneity and the effect of inert microbial mass. We have improved a 2D biofilm model based on cellular automata (CA) and used it to simulate multidimensional biofilms with active and inert biomass including a self-organizing development. Results indicate that the presence of inert biomass within biofilm structures does not change considerably the substrate flux into the biofilm because the active biomass is located at the surface of the biofilm. Long-term simulations revealed that although the biofilm system is highly heterogeneous and the microstructure is continuously changing, the biofilm reaches a dynamic steady-state with prediction of biofilm thickness and substrate flux stabilizing on a delimited range.
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Vyas, Heema K. N., Emma-Jayne Proctor, Jason McArthur, Jody Gorman, and Martina Sanderson-Smith. "Current Understanding of Group A Streptococcal Biofilms." Current Drug Targets 20, no. 9 (June 11, 2019): 982–93. http://dx.doi.org/10.2174/1389450120666190405095712.
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Background:It has been proposed that GAS may form biofilms. Biofilms are microbial communities that aggregate on a surface, and exist within a self-produced matrix of extracellular polymeric substances. Biofilms offer bacteria an increased survival advantage, in which bacteria persist, and resist host immunity and antimicrobial treatment. The biofilm phenotype has long been recognized as a virulence mechanism for many Gram-positive and Gram-negative bacteria, however very little is known about the role of biofilms in GAS pathogenesis.Objective:This review provides an overview of the current knowledge of biofilms in GAS pathogenesis. This review assesses the evidence of GAS biofilm formation, the role of GAS virulence factors in GAS biofilm formation, modelling GAS biofilms, and discusses the polymicrobial nature of biofilms in the oropharynx in relation to GAS.Conclusion:Further study is needed to improve the current understanding of GAS as both a monospecies biofilm, and as a member of a polymicrobial biofilm. Improved modelling of GAS biofilm formation in settings closely mimicking in vivo conditions will ensure that biofilms generated in the lab closely reflect those occurring during clinical infection.
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Ogawa, Akiko, Keito Takakura, Katsuhiko Sano, Hideyuki Kanematsu, Takehiko Yamano, Toshikazu Saishin, and Satoshi Terada. "Microbiome Analysis of Biofilms of Silver Nanoparticle-Dispersed Silane-Based Coated Carbon Steel Using a Next-Generation Sequencing Technique." Antibiotics 7, no. 4 (October 22, 2018): 91. http://dx.doi.org/10.3390/antibiotics7040091.
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Previously, we demonstrated that silver nanoparticle-dispersed silane-based coating could inhibit biofilm formation in conditions where seawater was used as a bacterial source and circulated in a closed laboratory biofilm reactor. However, it is still unclear whether the microbiome of a biofilm of silver nanoparticle-dispersed silane-based coating samples (Ag) differs from that of a biofilm of non-dispersed silane-based coating samples (Non-Ag). This study aimed to perform a microbiome analysis of the biofilms grown on the aforementioned coatings using a next-generation sequencing (NGS) technique. For this, a biofilm formation test was conducted by allowing seawater to flow through a closed laboratory biofilm reactor; subsequently, DNAs extracted from the biofilms of Ag and Non-Ag were used to prepare 16S rRNA amplicon libraries to analyze the microbiomes by NGS. Results of the operational taxonomy unit indicated that the biofilms of Non-Ag and Ag comprised one and no phyla of archaea, respectively, whereas Proteobacteria was the dominant phylum for both biofilms. Additionally, in both biofilms, Non-Ag and Ag, Marinomonas was the primary bacterial group involved in early stage biofilm formation, whereas Anaerospora was primarily involved in late-stage biofilm formation. These results indicate that silver nanoparticles will be unrelated to the bacterial composition of biofilms on the surface of silane-based coatings, while they control biofilm formation there.
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Bishop, Paul L., Tian C. Zhang, and Yun-Chang Fu. "Effects of biofilm structure, microbial distributions and mass transport on biodegradation processes." Water Science and Technology 31, no. 1 (January 1, 1995): 143–52. http://dx.doi.org/10.2166/wst.1995.0032.
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The influence of biofilm structure on transport and transformation processes in biofilms has been investigated microscopically using microelectrodes, a micro-slicing procedure and various chemical and microbiological tests. The study demonstrates that the biofilm structure is highly stratified, characterized by an increase of biofilm density, a decrease of metabolically active biomass, and a decrease of porosity with biofilm depth. Both the effective diffusivity for dissolved oxygen and the effectiveness factor decrease with biofilm depth. Competition for substrate and space in biofilms results in this stratified structure, which is also affected by biofilm thickness. The study reveals that there are different trends for the density increase and the decreases of porosity, microbial activity and DO effective diffusivity with biofilm depth for different biofilm thicknesses. The results of this study are helpful in obtaining a clearer physical description of biofilms, and help to bridge the gap between the mathematical modelling and external-phenomenon observation of biofilm systems.
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Lewandowski, Z., and H. Beyenal. "Biofilm monitoring: a perfect solution in search of a problem." Water Science and Technology 47, no. 5 (March 1, 2003): 9–18. http://dx.doi.org/10.2166/wst.2003.0267.
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The main problem with monitoring biofilms is data interpretation. Biofilm heterogeneity causes monitored parameters to vary from location to location in the same biofilm, and it is difficult to assess to what extent these variations are caused by biofilm heterogeneity and to what extent they reflect other properties of the biofilm. We have used the concept of discretized biofilms, which is an integrated system of biofilm monitoring and data interpretation, to assess the effect of biofilm heterogeneity on biofilm activity. Using this approach we have estimated that a heterogeneous biofilm can be ten times more active, in terms of glucose consumption rate, than a homogeneous biofilm of the same thickness but with uniformly distributed density.
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Ahimou, Francois, Michael J. Semmens, Greg Haugstad, and Paige J. Novak. "Effect of Protein, Polysaccharide, and Oxygen Concentration Profiles on Biofilm Cohesiveness." Applied and Environmental Microbiology 73, no. 9 (March 2, 2007): 2905–10. http://dx.doi.org/10.1128/aem.02420-06.
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ABSTRACT It is important to control biofilm cohesiveness to optimize process performance. In this study, a membrane-aerated biofilm reactor inoculated with activated sludge was used to grow mixed-culture biofilms of different ages and thicknesses. The cohesions, or cohesive energy levels per unit volume of biofilm, based on a reproducible method using atomic force microscopy (F. Ahimou, M. J. Semmens, P. J. Novak, and G. Haugstad, Appl. Environ. Microbiol. 73:2897-2904, 2007), were determined at different locations within the depths of the biofilms. In addition, the protein and polysaccharide concentrations within the biofilm depths, as well as the dissolved oxygen (DO) concentration profiles within the biofilms, were measured. It was found that biofilm cohesion increased with depth but not with age. Level of biofilm cohesive energy per unit volume was strongly correlated with biofilm polysaccharide concentration, which increased with depth in the membrane-aerated biofilm. In a 12-day-old biofilm, DO also increased with depth and may therefore be linked to polysaccharide production. In contrast, protein concentration was relatively constant within the biofilm and did not appear to influence cohesion.
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Klopper, Kyle B., Elanna Bester, and Gideon M. Wolfaardt. "Listeria monocytogenes Biofilms Are Planktonic Cell Factories despite Peracetic Acid Exposure under Continuous Flow Conditions." Antibiotics 12, no. 2 (January 19, 2023): 209. http://dx.doi.org/10.3390/antibiotics12020209.
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Listeria monocytogenes biofilms are ubiquitous in the food-processing environment, where they frequently show resistance against treatment with disinfectants such as peracetic acid (PAA) due to sub-lethal damage resulting in biofilm persistence or the formation of secondary biofilms. L. monocytogenes serovar ½a EGD-e biofilms were cultivated under continuous flow conditions at 10 °C, 22 °C, and 37 °C and exposed to industrially relevant PAA concentrations. The effect of PAA on biofilm metabolic activity and biomass was monitored in real-time using the CEMS-BioSpec system, in addition to daily measurement of biofilm-derived planktonic cell production. Biofilm-derived planktonic cell yields proved to be consistent with high yields during biofilm establishment (≥106 CFU.mL−1). The exposure of biofilms to the minimum inhibitory PAA concentration (0.16%) resulted in only a brief disruption in whole-biofilm metabolic activity and biofilm biomass accumulation. The recovered biofilm accumulated more biomass and greater activity, but cell yields remained similar. Increasing concentrations of PAA (0.50%, 1.5%, and 4.0%) had a longer-lasting inhibitory effect. Only the maximum dose resulted in a lasting inhibition of biofilm activity and biomass–a factor that needs due consideration in view of dilution in industrial settings. Better disinfection monitoring tools and protocols are required to adequately address the problem of Listeria biofilms in the food-processing environment, and more emphasis should be placed on biofilms serving as a “factory” for cell proliferation rather than only a survival mechanism.
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Yang, Shanshan, Xinfei Li, Weihe Cang, Delun Mu, Shuaiqi Ji, Yuejia An, Rina Wu, and Junrui Wu. "Biofilm tolerance, resistance and infections increasing threat of public health." Microbial Cell 10, no. 11 (November 6, 2023): 233–47. http://dx.doi.org/10.15698/mic2023.11.807.
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Microbial biofilms can cause chronic infection. In the clinical setting, the biofilm-related infections usually persist and reoccur; the main reason is the increased antibiotic resistance of biofilms. Traditional antibiotic therapy is not effective and might increase the threat of antibiotic resistance to public health. Therefore, it is urgent to study the tolerance and resistance mechanism of biofilms to antibiotics and find effective therapies for biofilm-related infections. The tolerance mechanism and host reaction of biofilm to antibiotics are reviewed, and bacterial biofilm related diseases formed by human pathogens are discussed thoroughly. The review also explored the role of biofilms in the development of bacterial resistance mechanisms and proposed therapeutic intervention strategies for biofilm related diseases.
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Peng, Qi, Xiaohua Tang, Wanyang Dong, Ning Sun, and Wenchang Yuan. "A Review of Biofilm Formation of Staphylococcus aureus and Its Regulation Mechanism." Antibiotics 12, no. 1 (December 22, 2022): 12. http://dx.doi.org/10.3390/antibiotics12010012.
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Bacteria can form biofilms in natural and clinical environments on both biotic and abiotic surfaces. The bacterial aggregates embedded in biofilms are formed by their own produced extracellular matrix. Staphylococcus aureus (S. aureus) is one of the most common pathogens of biofilm infections. The formation of biofilm can protect bacteria from being attacked by the host immune system and antibiotics and thus bacteria can be persistent against external challenges. Therefore, clinical treatments for biofilm infections are currently encountering difficulty. To address this critical challenge, a new and effective treatment method needs to be developed. A comprehensive understanding of bacterial biofilm formation and regulation mechanisms may provide meaningful insights against antibiotic resistance due to bacterial biofilms. In this review, we discuss an overview of S. aureus biofilms including the formation process, structural and functional properties of biofilm matrix, and the mechanism regulating biofilm formation.
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Kvist, Malin, Viktoria Hancock, and Per Klemm. "Inactivation of Efflux Pumps Abolishes Bacterial Biofilm Formation." Applied and Environmental Microbiology 74, no. 23 (October 3, 2008): 7376–82. http://dx.doi.org/10.1128/aem.01310-08.
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ABSTRACT Bacterial biofilms cause numerous problems in health care and industry; notably, biofilms are associated with a large number of infections. Biofilm-dwelling bacteria are particularly resistant to antibiotics, making it hard to eradicate biofilm-associated infections. Bacteria rely on efflux pumps to get rid of toxic substances. We discovered that efflux pumps are highly active in bacterial biofilms, thus making efflux pumps attractive targets for antibiofilm measures. A number of efflux pump inhibitors (EPIs) are known. EPIs were shown to reduce biofilm formation, and in combination they could abolish biofilm formation completely. Also, EPIs were able to block the antibiotic tolerance of biofilms. The results of this feasibility study might pave the way for new treatments for biofilm-related infections and may be exploited for prevention of biofilms in general.
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Ohashi, Akiyoshi, Takashi Koyama, Kazuaki Syutsubo, and Hideki Harada. "A novel method for evaluation of biofilm tensile strength resisting erosion." Water Science and Technology 39, no. 7 (April 1, 1999): 261–68. http://dx.doi.org/10.2166/wst.1999.0367.
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A novel methodology is proposed in this study to evaluate the tensile strength of biofilms by using a newly developed tensile test device. Three different types of biofilms were prepared for tensile test: Run 1 biofilm was aerobically cultivated on glucose, and Run 2 and Run 3 biofilms were denitrifying biofilms grown on glucose and on methanol, respectively, as a sole carbon source. Each of three biofilms was formed on the outer surfaces of tygon-made tubes (diameter 4.76 mm) submerged in a rectangular open-channel reactor. The results demonstrated that the tensile strengths of three different biofilms had a tendency to increase with the biofilm development over a period of 50 days of reactor operation and eventually reached a similar range, approximately 500 to 1000 Pa, independent of biofilm types or cultivation conditions. An elastic coefficient of the biofilm was determined by assuming that a biofilm behaves as an elastic material during the tensile test. A strong positive correlation was found between the elastic coefficient and the tensile strength. However, the behavior of extracellular biopolymer (ECP) content and the biofilm density were not dependent on the tensile strength. Scanning electron microscope (SEM) observations also suggested that the biofilm structural properties such as elastic coefficient are more determinative factors for the tensile strength than are the biofilm physiological properties such as ECP content.
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Tamayo, Rita, Bharathi Patimalla, and Andrew Camilli. "Growth in a Biofilm Induces a Hyperinfectious Phenotype in Vibrio cholerae." Infection and Immunity 78, no. 8 (June 1, 2010): 3560–69. http://dx.doi.org/10.1128/iai.00048-10.
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ABSTRACT Biofilm formation plays a multifaceted role in the life cycles of a wide variety of microorganisms. In the case of pathogenic Vibrio cholerae, biofilm formation in its native aquatic habitats is thought to aid in persistence during interepidemic seasons and to enhance infectivity upon oral ingestion. The structure of V. cholerae biofilms has been hypothesized to protect the bacteria during passage through the stomach. Here, we directly test the role of biofilm architecture in the infectivity of V. cholerae by comparing the abilities of intact biofilms, dispersed biofilms, and planktonic cells to colonize the mouse small intestine. Not only were V. cholerae biofilms better able to colonize than planktonic cells, but the structure of the biofilm was also found to be dispensable: intact and dispersed biofilms colonized equally, and both vastly out-colonized planktonic cells. The infectious dose for biofilm-derived V. cholerae was orders of magnitude lower than that of planktonic cells. This biofilm-induced hyperinfectivity may be due in part to a higher growth rate of biofilm-derived cells during infection. These results suggest that the infectious dose of naturally occurring biofilms of V. cholerae may be much lower than previously estimated using cells grown planktonically in vitro. Furthermore, this work implies the existence of factors specifically induced during growth in a biofilm that augment infection by V. cholerae.
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Wicks, Russell, Jegdish Babu, Franklin Garcia-Godoy, and Vinay Jain. "Comparison of Fungal Biofilm Formation on Three Contemporary Denture Base Materials." International Journal of Experimental Dental Science 4, no. 2 (2015): 104–8. http://dx.doi.org/10.5005/jp-journals-10029-1106.
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ABSTRACT Statement of problem: Modern polyamide ‘flexible’ denture base materials have increased in popularity for use in removable partial dentures in the last several years. The introduction of these newer products warrants investigation of their relative potential to develop fungal biofilms. Purpose The purpose of this study was to investigate the potential of three denture base materials to support fungal biofilm formation. Materials and methods Specimens of two ‘flexible’ nylon type materials and one traditional heat processed, methyl methacrylate resin material were studied (both polished and unpolished surfaces). The specimens were coated with saliva and evaluated for fungal (Candida albicans) biofilm formation. The fungal biofilm mass formed on denture substrates were evaluated by dry weight analysis and by determining the number of viable fungal cells in the biofilm by MTT viability assay. Alteration in fungal metabolic function following the treatment of the biofilm C. albicans with nystatin and fluconazole was determined by XTT assay. Results In general, the unpolished surfaces of the denture disks favored the fungal biofilm, the most being on polyamide specimen, Valplast. Significantly, less biofilm was formed on Duraflex and Lucitone surfaces. Biofim on C. albicans was also found to be resistant to antifungal agents. As compared to freshly incubated (grown) planktonic cells, biofilm fungal cells required significantly higher concentrations of nystatin and fluconazole in order to obtain 50% reduction in metabolic activity. Conclusion This study demonstrated the differences in denture materials to support fungal biofilm formation, and also difference between polished and unpolished denture material surfaces. The results demonstrated that one of the polyamide materials (duraflex) had lesser potential to biofilm formation than the others. Clinical significance Unfavorable tissue responses can ensue from the presence of fungal biofilms on dental prosthetics. Resistance to biofilm formation is a factor for dental materials in their selection and usage. This study helps to quantify, evaluate and compare biofilm formation on polished and unpolished surfaces of three commonly used denture base materials. The results of this study helped to identify materials, which may, therefore, be better indicated in clinical applications. Evaluations for the newer denture base materials, specific to these testing methods, appear to be novel in the scientific literature. How to cite this article Jain V, Babu J, Ahuja S, Wicks R, Garcia-Godoy F. Comparison of Fungal Biofilm Formation on Three Contemporary Denture Base Materials. Int J Experiment Dent Sci 2015;4(2):104-108.
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Chiou, Lan-Lin, Beatriz H. D. Panariello, Yusuke Hamada, Richard L. Gregory, Steven Blanchard, and Simone Duarte. "Comparison of In Vitro Biofilm Formation on Titanium and Zirconia Implants." BioMed Research International 2023 (April 15, 2023): 1–7. http://dx.doi.org/10.1155/2023/8728499.
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Background. Peri-implant diseases are emerging issues in contemporary implant dentistry. As biofilms play a critical role in peri-implant diseases, the characteristic of resisting bacterial adhesion would be ideal for dental implants. The aims of the study were to compare titanium (Ti) and zirconia (Zr) implants regarding the amount of biofilm formation at different time frames and assess the distribution of biofilm on different aspects of dental implants. Methods. Biofilm was developed on Ti and Zr dental implants with a peri-implant-related multispecies model with Streptococcus oralis, Actinomyces naeslundii, Veillonella dispar, and Porphyromonas gingivalis, for 3 and 14 days. Quantitative assessment was performed with the measurement of total bacterial viability (colony forming units, CFU/mg). Scanning electron microscopy (SEM) was used to evaluate biofilm formation on different aspects of the implants. Results. Three-day-old biofilm on Ti implants was significantly higher than that on Zr implants ( p < 0.001 ). The Ti and Zr groups were not significantly different for 14-day-old biofilm. SEM images demonstrated that 3-day-old biofilm on Zr implants was sparse while biofilm growth was more pronounced for 3-day-old biofilm on Ti implants and 14-day-old biofilm groups. It appeared that less biofilm formed on the valley compared to the thread top for 3-day-old biofilm on Zr implants. Differences between the valley and the thread top became indistinguishable with the development of mature biofilm. Conclusion. While early formed biofilms show greater accumulation on Ti implants compared to Zr implants, older biofilms between the two groups are comparable. The distribution of biofilms was not uniform on different areas of implant threads during early biofilm development.
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Samrot, Antony V., Amira Abubakar Mohamed, Etel Faradjeva, Lee Si Jie, Chin Hooi Sze, Akasha Arif, Tan Chuan Sean, et al. "Mechanisms and Impact of Biofilms and Targeting of Biofilms Using Bioactive Compounds—A Review." Medicina 57, no. 8 (August 18, 2021): 839. http://dx.doi.org/10.3390/medicina57080839.
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Biofilms comprising aggregates of microorganisms or multicellular communities have been a major issue as they cause resistance against antimicrobial agents and biofouling. To date, numerous biofilm-forming microorganisms have been identified, which have been shown to result in major effects including biofouling and biofilm-related infections. Quorum sensing (which describes the cell communication within biofilms) plays a vital role in the regulation of biofilm formation and its virulence. As such, elucidating the various mechanisms responsible for biofilm resistance (including quorum sensing) will assist in developing strategies to inhibit and control the formation of biofilms in nature. Employing biological control measures (such as the use of bioactive compounds) in targeting biofilms is of great interest since they naturally possess antimicrobial activity among other favorable attributes and can also possibly act as potent antibiofilm agents. As an effort to re-establish the current notion and understanding of biofilms, the present review discuss the stages involved in biofilm formation, the factors contributing to its development, the effects of biofilms in various industries, and the use of various bioactive compounds and their strategies in biofilm inhibition.
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Mokrzan, Elaine M., Michael O. Ward, and Lauren O. Bakaletz. "Type IV Pilus Expression Is Upregulated in Nontypeable Haemophilus influenzae Biofilms Formed at the Temperature of the Human Nasopharynx." Journal of Bacteriology 198, no. 19 (April 4, 2016): 2619–30. http://dx.doi.org/10.1128/jb.01022-15.
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ABSTRACTNontypeableHaemophilus influenzae(NTHI), a commensal of the human nasopharynx (hNP), is a common cause of biofilm-associated diseases of the respiratory tract. However, NTHI biofilm biology at the average hNP temperature, i.e., 34°C, has not been well studied. Here we grew NTHI biofilms at 34°C and 37°C, to evaluate relative biofilm growth, expression, and function of the type IV pilus (Tfp), a critical adhesin important for NTHI biofilm formation. The kinetics and regulation of Tfp expression in NTHI biofilms are unclear, especially at 34°C. Tfp expression, as estimated bypilApromoter activity, was distributed throughout the biofilms, with a unique pattern that was dependent on temperature, time in culture, and position within the maturing biofilm. Tfp expression was required for the formation of the characteristic tower structures of NTHI biofilms and was significantly upregulated in NTHI biofilms formed at 34°C versus 37°C. This increase correlated with significantly greater twitching motility at 34°C than at 37°C. Treatment with antisera targeting the major subunit of Tfp (PilA) significantly inhibited NTHI biofilm formation at both temperatures, confirming the importance of this critical adhesin in biofilm formation. Additionally, treatment of preestablished biofilms with antisera against PilA significantly decreased biofilm biomass and mean thickness at both temperatures. These results demonstrated a pivotal role for Tfp in NTHI biofilm formation and stability at the temperature of the hNP, and they underscore the utility of PilA as a vaccine candidate for treatment and/or prevention of NTHI biofilm-associated diseases.IMPORTANCENTHI is an important cause of chronic respiratory tract infections, including otitis media, chronic rhinosinusitis, and exacerbations of chronic obstructive pulmonary disease and cystic fibrosis. The chronic and recurrent nature of these diseases is attributed to the presence of bacterial biofilms, which are highly resistant to antimicrobials. We characterized NTHI biofilm growth and expression of PilA, the major subunit of the Tfp, at the temperature of the hNP, which is the commensal habitat of NTHI. Our results expand the current understanding of the role of Tfp during biofilm formation and maturation at the temperature of both the hNP and the middle ear, and they strengthen support for PilA as a vaccine candidate for the prevention and treatment of NTHI biofilm-associated diseases.
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Ito, Akinobu, Asami Taniuchi, Thithiwat May, Koji Kawata, and Satoshi Okabe. "Increased Antibiotic Resistance of Escherichia coli in Mature Biofilms." Applied and Environmental Microbiology 75, no. 12 (April 17, 2009): 4093–100. http://dx.doi.org/10.1128/aem.02949-08.
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ABSTRACT Biofilms are considered to be highly resistant to antimicrobial agents. Several mechanisms have been proposed to explain this high resistance of biofilms, including restricted penetration of antimicrobial agents into biofilms, slow growth owing to nutrient limitation, expression of genes involved in the general stress response, and emergence of a biofilm-specific phenotype. However, since combinations of these factors are involved in most biofilm studies, it is still difficult to fully understand the mechanisms of biofilm resistance to antibiotics. In this study, the antibiotic susceptibility of Escherichia coli cells in biofilms was investigated with exclusion of the effects of the restricted penetration of antimicrobial agents into biofilms and the slow growth owing to nutrient limitation. Three different antibiotics, ampicillin (100 μg/ml), kanamycin (25 μg/ml), and ofloxacin (10 μg/ml), were applied directly to cells in the deeper layers of mature biofilms that developed in flow cells after removal of the surface layers of the biofilms. The results of the antibiotic treatment analyses revealed that ofloxacin and kanamycin were effective against biofilm cells, whereas ampicillin did not kill the cells, resulting in regrowth of the biofilm after the ampicillin treatment was discontinued. LIVE/DEAD staining revealed that a small fraction of resistant cells emerged in the deeper layers of the mature biofilms and that these cells were still alive even after 24 h of ampicillin treatment. Furthermore, to determine which genes in the biofilm cells are induced, allowing increased resistance to ampicillin, global gene expression was analyzed at different stages of biofilm formation, the attachment, colony formation, and maturation stages. The results showed that significant changes in gene expression occurred during biofilm formation, which were partly induced by rpoS expression. Based on the experimental data, it is likely that the observed resistance of biofilms can be attributed to formation of ampicillin-resistant subpopulations in the deeper layers of mature biofilms but not in young colony biofilms and that the production and resistance of the subpopulations were aided by biofilm-specific phenotypes, like slow growth and induction of rpoS-mediated stress responses.
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Govaert, Marlies, Cindy Smet, Maria Baka, Branimir Ećimović, James L. Walsh, and Jan Van Impe. "Resistance of L. monocytogenes and S. Typhimurium towards Cold Atmospheric Plasma as Function of Biofilm Age." Applied Sciences 8, no. 12 (December 19, 2018): 2702. http://dx.doi.org/10.3390/app8122702.
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The biofilm mode of growth protects bacterial cells against currently applied disinfection methods for abiotic (food) contact surfaces. Therefore, innovative methods, such as Cold Atmospheric Plasma (CAP), should be investigated for biofilm inactivation. However, more knowledge is required concerning the influence of the biofilm age on the inactivation efficacy in order to comment on a possible application of CAP in the (food) processing industry. L. monocytogenes and S. Typhimurium biofilms with five different ages (i.e., 1, 2, 3, 7, and 10 days) were developed. For the untreated biofilms, the total biofilm mass and the cell density were determined. To investigate the biofilm resistance towards CAP treatment, biofilms with different ages were treated for 10 min and the remaining cell density was determined. Finally, for the one-day old reference biofilms and the most resistant biofilm age, complete inactivation curves were developed to examine the influence of the biofilm age on the inactivation kinetics. For L. monocytogenes, an increased biofilm age resulted in (i) an increased biomass, (ii) a decreased cell density prior to CAP treatment, and (iii) an increased resistance towards CAP treatment. For S. Typhimurium, similar results were obtained, except for the biomass, which was here independent of the biofilm age.
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Lazarova, V. Z., B. Capdeville, and L. Nikolov. "Biofilm Performance of a Fluidized Bed Biofilm Reactor for Drinking Water Denitrification." Water Science and Technology 26, no. 3-4 (August 1, 1992): 555–66. http://dx.doi.org/10.2166/wst.1992.0435.
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The properties of two biofilms generated with different predominant organisms were studied in a laboratory-scale fluidized bed bioreactor. Bed expansion, biofilm thickness, biofilm density, protein and polysaccharide concentrations were measured and compared. A high polysaccharide concentration was observed in the less dense and more fragile biofilm of Ps. aeruginosa. The more active biofilm of Ps. stutzeri was characterized by higher protein concentration and density. The results demonstrated that the biofilm performance mostly depended on the physiological characteristics of the preponderant organism. Complete nitrate reduction was reached in both biofilms at very low biofilm thickness. Elevated residual nitrite was observed only in the biofilm of Ps. aeruginosa.
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Pavissich, J. P., M. Aybar, K. J. Martin, and R. Nerenberg. "A methodology to assess the effects of biofilm roughness on substrate fluxes using image analysis, substrate profiling, and mathematical modelling." Water Science and Technology 69, no. 9 (March 3, 2014): 1932–41. http://dx.doi.org/10.2166/wst.2014.103.
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We present a novel approach, based on image analysis and modelling, to study the impact of morphological variability (roughness) and fluid dynamics on substrate mass fluxes in biofilms. Specifically, we used this method to assess substrate fluxes in counter-diffusional autotrophic biofilms in a hydrogen-based membrane biofilm reactor. The physical structure of the biofilm was determined in situ at the meso-scale using stereomicroscopy. Image analysis was used to characterize the biofilm structure, and substrate profiles were obtained using microsensors. A two-dimensional, continuum biofilm model including microbial reactions, mass transport, and fluid dynamics was developed to compute substrate conversion in irregularly shaped counter-diffusional biofilms. Experimental biofilm structures were reproduced in the model and simulated under the prevailing substrate and hydrodynamic conditions for flow velocities varied over three orders of magnitude. Model calculations were consistent with experimental results and showed enhanced conversion rates with increased roughness at higher flow velocities. Also, modelling showed that conversion rates in counter-diffusional biofilms were typically higher than in co-diffusional biofilms. This study highlights the potential to use a simple image acquisition approach coupled to a theoretical model, to evaluate biofilm overall substrate utilization related to biofilm morphological heterogeneity.
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Dakheel, Khulood Hamid, Raha Abdul Rahim, Vasantha Kumari Neela, Jameel R. Al-Obaidi, Tan Geok Hun, and Khatijah Yusoff. "Methicillin-ResistantStaphylococcus aureusBiofilms and Their Influence on Bacterial Adhesion and Cohesion." BioMed Research International 2016 (2016): 1–14. http://dx.doi.org/10.1155/2016/4708425.
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Twenty-five methicillin-resistantStaphylococcus aureus(MRSA) isolates were characterized by staphylococcal protein A gene typing and the ability to form biofilms. The presence of exopolysaccharides, proteins, and extracellular DNA and RNA in biofilms was assessed by a dispersal assay. In addition, cell adhesion to surfaces and cell cohesion were evaluated using the packed-bead method and mechanical disruption, respectively. The predominant genotype wasspatype t127 (22 out of 25 isolates); the majority of isolates were categorized as moderate biofilm producers. Twelve isolates displayed PIA-independent biofilm formation, while the remaining 13 isolates were PIA-dependent. Both groups showed strong dispersal in response to RNase and DNase digestion followed by proteinase K treatment. PIA-dependent biofilms showed variable dispersal after sodium metaperiodate treatment, whereas PIA-independent biofilms showed enhanced biofilm formation. There was no correlation between the extent of biofilm formation or biofilm components and the adhesion or cohesion abilities of the bacteria, but the efficiency of adherence to glass beads increased after biofilm depletion. In conclusion, nucleic acids and proteins formed the main components of the MRSA clone t127 biofilm matrix, and there seems to be an association between adhesion and cohesion in the biofilms tested.
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Mukherjee, Pranab K., Sotohy Mohamed, Jyotsna Chandra, Duncan Kuhn, Shuqing Liu, Omar S. Antar, Ryan Munyon, et al. "Alcohol Dehydrogenase Restricts the Ability of the Pathogen Candida albicans To Form a Biofilm on Catheter Surfaces through an Ethanol-Based Mechanism." Infection and Immunity 74, no. 7 (July 2006): 3804–16. http://dx.doi.org/10.1128/iai.00161-06.
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ABSTRACT Candida biofilms formed on indwelling medical devices are increasingly associated with severe infections. In this study, we used proteomics and Western and Northern blotting analyses to demonstrate that alcohol dehydrogenase (ADH) is downregulated in Candida biofilms. Disruption of ADH1 significantly (P = 0.0046) enhanced the ability of Candida albicans to form biofilm. Confocal scanning laser microscopy showed that the adh1 mutant formed thicker biofilm than the parent strain (210 μm and 140 μm, respectively). These observations were extended to an engineered human oral mucosa and an in vivo rat model of catheter-associated biofilm. Inhibition of Candida ADH enzyme using disulfiram and 4-methylpyrazole resulted in thicker biofilm (P < 0.05). Moreover, biofilms formed by the adh1 mutant strain produced significantly smaller amounts of ethanol, but larger amounts of acetaldehyde, than biofilms formed by the parent and revertant strains (P < 0.0001), demonstrating that the effect of Adh1p on biofilm formation is mediated by its enzymatic activity. Furthermore, we found that 10% ethanol significantly inhibited biofilm formation in vitro, with complete inhibition of biofilm formation at ethanol concentrations of ≥20%. Similarly, using a clinically relevant rabbit model of catheter-associated biofilm, we found that ethanol treatment inhibited biofilm formation by C. albicans in vivo (P < 0.05) but not by Staphylococcus spp. (P > 0.05), indicating that ethanol specifically inhibits Candida biofilm formation. Taken together, our studies revealed that Adh1p contributes to the ability of C. albicans to form biofilms in vitro and in vivo and that the protein restricts biofilm formation through an ethanol-dependent mechanism. These results are clinically relevant and may suggest novel antibiofilm treatment strategies.
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Purevdorj, B., J. W. Costerton, and P. Stoodley. "Influence of Hydrodynamics and Cell Signaling on the Structure and Behavior of Pseudomonas aeruginosa Biofilms." Applied and Environmental Microbiology 68, no. 9 (September 2002): 4457–64. http://dx.doi.org/10.1128/aem.68.9.4457-4464.2002.
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ABSTRACT Biofilms were grown from wild-type (WT) Pseudomonas aeruginosa PAO1 and the cell signaling lasI mutant PAO1-JP1 under laminar and turbulent flows to investigate the relative contributions of hydrodynamics and cell signaling for biofilm formation. Various biofilm morphological parameters were quantified using Image Structure Analyzer software. Multivariate analysis demonstrated that both cell signaling and hydrodynamics significantly (P < 0.000) influenced biofilm structure. In turbulent flow, both biofilms formed streamlined patches, which in some cases developed ripple-like wave structures which flowed downstream along the surface of the flow cell. In laminar flow, both biofilms formed monolayers interspersed with small circular microcolonies. Ripple-like structures also formed in four out of six WT biofilms, although their velocity was approximately 10 times less than that of those that formed in the turbulent flow cells. The movement of biofilm cell clusters over solid surfaces may have important clinical implications for the dissemination of biofilm subject to fluid shear, such as that found in catheters. The ability of the cell signaling mutant to form biofilms in high shear flow demonstrates that signaling mechanisms are not required for the formation of strongly adhered biofilms. Similarity between biofilm morphologies in WT and mutant biofilms suggests that the dilution of signal molecules by mass transfer effects in faster flowing systems mollifies the dramatic influence of signal molecules on biofilm structure reported in previous studies.
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Hamzah, Hasyrul, Triana Hertiani, Sylvia Utami Tunjung Pratiwi, Titik Nuryastuti, and Yosi Bayu Murti. "The biofilm inhibition and eradication activity of curcumin againts polymicrobial biofilm." BIO Web of Conferences 28 (2020): 04001. http://dx.doi.org/10.1051/bioconf/20202804001.
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Curcumin is a polyphenol compound that is a member of the ginger family (Zingiberaceae), which has potential as an antibacterial, antifungal, and polymicrobial antibiofilm on the catheter. Still, its inhibitory activity and eradication of non-catheter polymicrobial antibiotics against S. aureus, P. aeruginosa, E. coli, and C. albicans have never been reported. The discovery of a candidate polymicrobial anti-biofilm drug is indispensable for overcoming infections associated with biofilms. This study aims to determine the inhibitory activity and eradication of curcumin on polymicrobial biofilms. Inhibition testing and eradication activity of polymicrobial biofilms were performed using the microtiter broth method. The effectiveness of curcumin on polymicrobial biofilms was analyzed using minimum biofilm inhibition concentration (MBIC50) and minimum biofilm eradication concentration (MBEC50). The mechanism of action of curcumin against polymicrobial biofilms is tested using scanning electron microscopy (SEM). Curcumin 1 % b/v gives biofilm inhibition activity in the mid-phase and maturation of 62.23 % ± 0.01, 59.43 % ± 0.01, and can eradicate polymicrobial biofilms by 55.79 % ± 0.01 and not much different with nystatin drug control activity. The results also provide evidence that curcumin can damage the extracellular polymeric matrix (EPS) polymicrobial biofilms of S. aureus, P. aeruginosa, E. coli, and C. albicans and damage the morphology of polymicrobial biofilms. Therefore, curcumin can be developed as a candidate for new antibiofilm drugs against polymicrobial biofilms S. aureus, P. aeruginosa, E. coli dan C albicabs.
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Dranguet, Perrine, Vera I. Slaveykova, and Séverine Le Faucheur. "Kinetics of mercury accumulation by freshwater biofilms." Environmental Chemistry 14, no. 7 (2017): 458. http://dx.doi.org/10.1071/en17073.
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Environmental contextMercury (Hg) is a major environmental contaminant due to its toxicity, accumulation and biomagnification along the food chain. We demonstrate that Hg accumulation by biofilms, one possible entry point for Hg into food webs, is rapid and depends on biofilm structure and composition. These findings have important implications for the understanding of Hg bioavailability and effects towards aquatic microorganisms. AbstractMercury contamination is of high concern due to its bioaccumulation, toxicity and biomagnification along the food chain. Biofilms can accumulate Hg and contribute to its incorporation in freshwater food webs. Nevertheless, the accumulation kinetics of Hg by biofilms is not well described and understood. The aim of the present study was thus to gain mechanistic understanding of Hg accumulation by biofilms. Kinetics of Hg uptake by biofilms of different ages (e.g. different compositions) was characterised by determining Hg contents in biofilms with and without a cysteine-washing step. Hg accumulation was rapid in both biofilms, with the uptake rate constant of the younger biofilm 10 times higher than that of the older biofilm. Moreover, accumulated Hg reached a plateau at 24h exposure in the younger biofilm, whereas it increased linearly in the older biofilm. The observed difference in Hg uptake by the studied biofilms is likely a result of the difference in biofilm thickness (and thus Hg diffusion inside the biofilm matrix) and microbial composition. These findings have important implications for the understanding of Hg bioavailability and effects towards aquatic microorganisms.
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Uzuegbunam, Ngozi V., Faruk A. Umar, and Bassey Enya Bassey. "Biofilm Detection on Catheter Associated Uropathogenic Bacteriuria among Fistula Patients Attending National Obstetric Fistula Centre Ningi, Bauchi State, Nigeria." European Journal of Medical and Health Sciences 3, no. 2 (April 26, 2021): 180–84. http://dx.doi.org/10.24018/ejmed.2021.3.2.803.
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Background: Biofilm production caused by bacteria plays a vital role in catheter associated urinary tract infection (UTI) or bacteriuria being responsible for persistence and recurrent infection. Biofilms forming bacteria are difficult to eradicate due to antimicrobial resistance to the commonly used antibiotic. Biofilms are currently estimated to be responsible for over 65% of nosocomial infections and 80% of microbial infections. This study aimed to perform biofilm detection on uropathogenic bacterial isolates among fistula patients attending National Obstetric Fistula centre Ningi and investigate the antimicrobial susceptibility pattern.
Methods: A total of 217 strains of significant bacteriuria were isolated from vesico vaginal fistula (VVF) patients. A cross sectional study was conducted at the hospital. The urine samples were collected and cultured on CLED and blood agar media while confirmation was done using their biochemical reaction. The detection of biofilms formation on the isolates was performed using tube adherence and Congo red agar method. Antimicrobial susceptibility testing was carried out by disc diffusion method on Muller Hinton agar.
Results: Out of 217 significant bacteriuria isolated, 38 strains produced biofilms;28 strains tested positive on tube adherence method while 15 strains were positive on Congo red agar method. Bacteria that produced biofim showed multiple drug resistance compared to the platonic bacterial cells. All the biofilm producers showed 100% resistant to septrin, ampiclox, gentamycin and amoxicillin. There was no significant value between tube adherence and Congo red agar method with P value > 0.05.
Conclusion: Biofilm detection should form part of routine testing while antimicrobial susceptibility testing is paramount on better choice of antibiotic therapy for proper management to reduce economic lost, treatment failure and drug resistance.
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Donlan, Rodney M., and J. William Costerton. "Biofilms: Survival Mechanisms of Clinically Relevant Microorganisms." Clinical Microbiology Reviews 15, no. 2 (April 2002): 167–93. http://dx.doi.org/10.1128/cmr.15.2.167-193.2002.
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SUMMARY Though biofilms were first described by Antonie van Leeuwenhoek, the theory describing the biofilm process was not developed until 1978. We now understand that biofilms are universal, occurring in aquatic and industrial water systems as well as a large number of environments and medical devices relevant for public health. Using tools such as the scanning electron microscope and, more recently, the confocal laser scanning microscope, biofilm researchers now understand that biofilms are not unstructured, homogeneous deposits of cells and accumulated slime, but complex communities of surface-associated cells enclosed in a polymer matrix containing open water channels. Further studies have shown that the biofilm phenotype can be described in terms of the genes expressed by biofilm-associated cells. Microorganisms growing in a biofilm are highly resistant to antimicrobial agents by one or more mechanisms. Biofilm-associated microorganisms have been shown to be associated with several human diseases, such as native valve endocarditis and cystic fibrosis, and to colonize a wide variety of medical devices. Though epidemiologic evidence points to biofilms as a source of several infectious diseases, the exact mechanisms by which biofilm-associated microorganisms elicit disease are poorly understood. Detachment of cells or cell aggregates, production of endotoxin, increased resistance to the host immune system, and provision of a niche for the generation of resistant organisms are all biofilm processes which could initiate the disease process. Effective strategies to prevent or control biofilms on medical devices must take into consideration the unique and tenacious nature of biofilms. Current intervention strategies are designed to prevent initial device colonization, minimize microbial cell attachment to the device, penetrate the biofilm matrix and kill the associated cells, or remove the device from the patient. In the future, treatments may be based on inhibition of genes involved in cell attachment and biofilm formation.
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Zhang, Yunhui, Gilles Brackman, and Tom Coenye. "Pitfalls associated with evaluating enzymatic quorum quenching activity: the case of MomL and its effect onPseudomonas aeruginosaandAcinetobacter baumanniibiofilms." PeerJ 5 (April 27, 2017): e3251. http://dx.doi.org/10.7717/peerj.3251.
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BackgroundThe enzymatic degradation of quorums sensing (QS) molecules (called quorum quenching, QQ) has been considered as a promising anti-virulence therapy to treat biofilm-related infections and combat antibiotic resistance. The recently-discovered QQ enzyme MomL has been reported to efficiently degrade differentN-acyl homoserine lactones (AHLs) of various Gram-negative pathogens. Here we investigated the effect of MomL on biofilms formed by two important nosocomial pathogens,Pseudomonas aeruginosaandAcinetobacter baumannii.MethodsMomL was expressed inE.coliBL21 and purified. The activity of MomL on AHLs with hydroxyl substituent was tested. Biofilms ofP. aeruginosaPAO1 andAcinetobacterstrains were formed in 96-well microtiter plates. Biofilm formation was evaluated by crystal violet staining, plating and fluorescence microscopy. The effect of MomL on biofilm susceptibility to antibiotics was also tested. We further evaluated MomL in dual-species biofilms formed byP. aeruginosaandA. baumannii, and in biofilms formed in a wound model. The effect of MomL on virulence ofA. baumanniiwas also tested in theCaenorhabditis elegansmodel.ResultsMomL reduced biofilm formation and increased biofilm susceptibility to different antibiotics in biofilms ofP. aeruginosaPAO1 andA. baumanniiLMG 10531 formed in microtiter platesin vitro. However, no significant differences were detected in the dual-species biofilm and in wound model biofilms. In addition, MomL did not affect virulence ofA. baumanniiin theC. elegansmodel. Finally, the effect of MomL on biofilm ofAcinetobacterstrains seems to be strain-dependent.DiscussionOur results indicate that although MomL showed a promising anti-biofilm effect againstP. aeruginosaandA. baumaniibiofilms formed in microtiter plates, the effect on biofilm formation under conditions more likely to mimic the real-life situation was much less pronounced or even absent. Our data indicate that in order to obtain a better picture of potential applicability of QQ enzymes for the treatment of biofilm-related infections, more elaborate model systems need to be used.
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Biočanin, Marjan, Haowa Madi, Zorica Vasiljević, Milan Kojić, Branko Jovčić, and Jelena Lozo. "Temperature, pH and Trimethoprim-Sulfamethoxazole Are Potent Inhibitors of Biofilm Formation by Stenotrophomonas maltophilia Clinical Isolates." Polish Journal of Microbiology 66, no. 4 (December 4, 2017): 433–38. http://dx.doi.org/10.5604/01.3001.0010.6996.
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Stenotrophomonas maltophilia, an opportunistic pathogen usually connected with healthcare-associated infections, is an environmental bacterium. Intrinsic resistance to multiple antibiotics, with different virulence determinants in the last decade classified this bacterium in the group of global multiple drug resistant (MDR) organism. S. maltophilia clinical isolates, were collected from tertiary care pediatric hospital in Belgrade, Serbia to investigate influence of different factors on biofilm formation, kinetics of biofilm formation for strong biofilm producers and effect of trimethoprim-sulfamethoxazole (TMP/SMX) on formed biofilm. Most of the isolates (89.8%) were able to form a biofilm. Analysis of biofilm formation in different growth conditions showed that changing of temeperature and pH had the stronggest effect on biofilm formation almost equally in group of cystic fibrosis (CF) and non-CF strains. TMP/SMX in concentration of 50 μg/ml reduced completely 24 h old biofilms while concentration of 25 μg/ml effects formed biofilms in a strain dependent manner. Among strains able to form strong biofilm CF isolates formed biofilm slower than non-CF isolates, while shaking conditions did not affect biofilm formation. Swimming motility was detected in both CF and non-CF isolates, however more motile strain formed stronger biofilms. This study suggests that temperature, pH and TMP/SMX had the strongest influence on biofilm formation in analyzed collection of S. maltophilia. A positive correlation between motility and strength of formed biofilm was demonstrated.
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Yasir, Muhammad, Mark Willcox, and Debarun Dutta. "Action of Antimicrobial Peptides against Bacterial Biofilms." Materials 11, no. 12 (December 5, 2018): 2468. http://dx.doi.org/10.3390/ma11122468.
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Microbes are known to colonize surfaces and form biofilms. These biofilms are communities of microbes encased in a self-produced matrix that often contains polysaccharides, DNA and proteins. Antimicrobial peptides (AMPs) have been used to control the formation and to eradicate mature biofilms. Naturally occurring or synthetic antimicrobial peptides have been shown to prevent microbial colonization of surfaces, to kill bacteria in biofilms and to disrupt the biofilm structure. This review systemically analyzed published data since 1970 to summarize the possible anti-biofilm mechanisms of AMPs. One hundred and sixty-two published reports were initially selected for this review following searches using the criteria ‘antimicrobial peptide’ OR ‘peptide’ AND ‘mechanism of action’ AND ‘biofilm’ OR ‘antibiofilm’ in the databases PubMed; Scopus; Web of Science; MEDLINE; and Cochrane Library. Studies that investigated anti-biofilm activities without describing the possible mechanisms were removed from the analysis. A total of 17 original reports were included which have articulated the mechanism of antimicrobial action of AMPs against biofilms. The major anti-biofilm mechanisms of antimicrobial peptides are: (1) disruption or degradation of the membrane potential of biofilm embedded cells; (2) interruption of bacterial cell signaling systems; (3) degradation of the polysaccharide and biofilm matrix; (4) inhibition of the alarmone system to avoid the bacterial stringent response; (5) downregulation of genes responsible for biofilm formation and transportation of binding proteins.
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Rahmani-Badi, Azadeh, Shayesteh Sepehr, Parisa Mohammadi, Mohammad Reza Soudi, Hamta Babaie-Naiej, and Hossein Fallahi. "A combination of cis-2-decenoic acid and antibiotics eradicates pre-established catheter-associated biofilms." Journal of Medical Microbiology 63, no. 11 (November 1, 2014): 1509–16. http://dx.doi.org/10.1099/jmm.0.075374-0.
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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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Naclerio, George A., Kenneth I. Onyedibe, and Herman O. Sintim. "Lipoteichoic Acid Biosynthesis Inhibitors as Potent Inhibitors of S. aureus and E. faecalis Growth and Biofilm Formation." Molecules 25, no. 10 (May 12, 2020): 2277. http://dx.doi.org/10.3390/molecules25102277.
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Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecalis (VRE) have been deemed as serious threats by the CDC. Many chronic MRSA and VRE infections are due to biofilm formation. Biofilm are considered to be between 10–10,000 times more resistant to antibiotics, and therefore new chemical entities that inhibit and/or eradicate biofilm formation are needed. Teichoic acids, such as lipoteichoic acids (LTAs) and wall teichoic acids (WTAs), play pivotal roles in Gram-positive bacteria’s ability to grow, replicate, and form biofilms, making the inhibition of these teichoic acids a promising approach to fight infections by biofilm forming bacteria. Here, we describe the potent biofilm inhibition activity against MRSA and VRE biofilms by two LTA biosynthesis inhibitors HSGN-94 and HSGN-189 with MBICs as low as 0.0625 µg/mL against MRSA biofilms and 0.5 µg/mL against VRE biofilms. Additionally, both HSGN-94 and HSGN-189 were shown to potently synergize with the WTA inhibitor Tunicamycin in inhibiting MRSA and VRE biofilm formation.
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Drescher, Knut, Jörn Dunkel, Carey D. Nadell, Sven van Teeffelen, Ivan Grnja, Ned S. Wingreen, Howard A. Stone, and Bonnie L. Bassler. "Architectural transitions in Vibrio cholerae biofilms at single-cell resolution." Proceedings of the National Academy of Sciences 113, no. 14 (March 1, 2016): E2066—E2072. http://dx.doi.org/10.1073/pnas.1601702113.
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Many bacterial species colonize surfaces and form dense 3D structures, known as biofilms, which are highly tolerant to antibiotics and constitute one of the major forms of bacterial biomass on Earth. Bacterial biofilms display remarkable changes during their development from initial attachment to maturity, yet the cellular architecture that gives rise to collective biofilm morphology during growth is largely unknown. Here, we use high-resolution optical microscopy to image all individual cells in Vibrio cholerae biofilms at different stages of development, including colonies that range in size from 2 to 4,500 cells. From these data, we extracted the precise 3D cellular arrangements, cell shapes, sizes, and global morphological features during biofilm growth on submerged glass substrates under flow. We discovered several critical transitions of the internal and external biofilm architectures that separate the major phases of V. cholerae biofilm growth. Optical imaging of biofilms with single-cell resolution provides a new window into biofilm formation that will prove invaluable to understanding the mechanics underlying biofilm development.
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Yin, Wen, Yiting Wang, Lu Liu, and Jin He. "Biofilms: The Microbial “Protective Clothing” in Extreme Environments." International Journal of Molecular Sciences 20, no. 14 (July 12, 2019): 3423. http://dx.doi.org/10.3390/ijms20143423.
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Microbial biofilms are communities of aggregated microbial cells embedded in a self-produced matrix of extracellular polymeric substances (EPS). Biofilms are recalcitrant to extreme environments, and can protect microorganisms from ultraviolet (UV) radiation, extreme temperature, extreme pH, high salinity, high pressure, poor nutrients, antibiotics, etc., by acting as “protective clothing”. In recent years, research works on biofilms have been mainly focused on biofilm-associated infections and strategies for combating microbial biofilms. In this review, we focus instead on the contemporary perspectives of biofilm formation in extreme environments, and describe the fundamental roles of biofilm in protecting microbial exposure to extreme environmental stresses and the regulatory factors involved in biofilm formation. Understanding the mechanisms of biofilm formation in extreme environments is essential for the employment of beneficial microorganisms and prevention of harmful microorganisms.
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Hill, Walter R., Angela T. Bednarek, and I. Lauren Larsen. "Cadmium sorption and toxicity in autotrophic biofilms." Canadian Journal of Fisheries and Aquatic Sciences 57, no. 3 (March 1, 2000): 530–37. http://dx.doi.org/10.1139/f99-286.
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Autotrophic biofilms (periphyton) accumulate substantial quantities of metals from contaminated water. In this study, we measured the time course of biofilm cadmium sorption, examined the effects of current, biomass, and light on short-term cadmium sorption by biofilms, and tested the toxicity of cadmium to biofilm photosynthesis. The time course of cadmium sorption appeared to be a linear function of time over the 48-h measurement period. Biofilms in current [Formula: see text]2 cm·s-1 sorbed three to five times more cadmium than biofilms in still water. Cadmium sorbed after 4 h was 75% greater in high-biomass biofilm (2.5 mg dry mass·cm-2) than in low-biomass biofilm (0.5 mg dry mass·cm-2), but only in moving water. Light enhanced the sorption of cadmium 40% in one biofilm type. Cadmium toxicity to photo synthesis was evident after 24 h in thin biofilms exposed to initial cadmium concentrations [Formula: see text]10 μg·L-1; photosynthesis by thicker biofilms was not significantly impaired even at the highest concentration (100 μg·L-1). Variations in current, biofilm biomass, and light are likely to influence the movement of metals in flowing systems.
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Hong, Wenzhou, Bing Pang, Shayla West-Barnette, and W. Edward Swords. "Phosphorylcholine Expression by Nontypeable Haemophilus influenzae Correlates with Maturation of Biofilm Communities In Vitro and In Vivo." Journal of Bacteriology 189, no. 22 (June 15, 2007): 8300–8307. http://dx.doi.org/10.1128/jb.00532-07.
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ABSTRACT Nontypeable Haemophilus influenzae (NTHI) causes chronic infections that feature the formation of biofilm communities. NTHI variants within biofilms have on their surfaces lipooligosaccharides containing sialic acid (NeuAc) and phosphorylcholine (PCho). Our work showed that NeuAc promotes biofilm formation, but we observed no defect in the initial stages of biofilm formation for mutants lacking PCho. In this study, we asked if alterations in NTHI PCho content affect later stages of biofilm maturation. Biofilm communities were compared for NTHI 2019 and isogenic mutants that either lacked PCho (NTHI 2019 licD) or were constitutively locked in the PCho-positive phase (NTHI 2019 lic ON ). Transformants expressing green fluorescent protein were cultured in continuous-flow biofilms and analyzed by confocal laser scanning microscopy. COMSTAT was used to quantify different biofilm parameters. PCho expression correlated significantly with increased biofilm thickness, surface coverage, and total biomass, as well as with a decrease in biofilm roughness. Comparable results were obtained by scanning electron microscopy. Analysis of thin sections of biofilms by transmission electron microscopy revealed shedding of outer membrane vesicles by NTHI bacteria within biofilms and staining of matrix material with ruthenium red in biofilms formed by NTHI 2019 lic ON . The biofilms of all three strains were comparable in viability, the presence of extracellular DNA, and the presence of sialylated moieties on or between bacteria. In vivo infection studies using the chinchilla model of otitis media showed a direct correlation between PCho expression and biofilm formation within the middle-ear chamber and an inverse relationship between PCho and persistence in the planktonic phase in middle-ear effusions. Collectively, these data show that PCho correlates with, and may promote, the maturation of NTHI biofilms. Further, this structure may be disadvantageous in the planktonic phase.
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Hu, Zhiqiang, Gabriela Hidalgo, Paul L. Houston, Anthony G. Hay, Michael L. Shuler, Héctor D. Abruña, William C. Ghiorse, and Leonard W. Lion. "Determination of Spatial Distributions of Zinc and Active Biomass in Microbial Biofilms by Two-Photon Laser Scanning Microscopy." Applied and Environmental Microbiology 71, no. 7 (July 2005): 4014–21. http://dx.doi.org/10.1128/aem.71.7.4014-4021.2005.
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ABSTRACT The spatial distributions of zinc, a representative transition metal, and active biomass in bacterial biofilms were determined using two-photon laser scanning microscopy (2P-LSM). Application of 2P-LSM permits analysis of thicker biofilms than are amenable to observation with confocal laser scanning microscopy and also provides selective excitation of a smaller focal volume with greater depth localization. Thin Escherichia coli PHL628 biofilms were grown in a minimal mineral salts medium using pyruvate as the carbon and energy source under batch conditions, and thick biofilms were grown in Luria-Bertani medium using a continuous-flow drip system. The biofilms were visualized by 2P-LSM and shown to have heterogeneous structures with dispersed dense cell clusters, rough surfaces, and void spaces. Contrary to homogeneous biofilm model predictions that active biomass would be located predominantly in the outer regions of the biofilm and inactive or dead biomass (biomass debris) in the inner regions, significant active biomass fractions were observed at all depths in biofilms (up to 350 μm) using live/dead fluorescent stains. The active fractions were dependent on biofilm thickness and are attributed to the heterogeneous characteristics of biofilm structures. A zinc-binding fluorochrome (8-hydroxy-5-dimethylsulfoamidoquinoline) was synthesized and used to visualize the spatial location of added Zn within biofilms. Zn was distributed evenly in a thin (12 μm) biofilm but was located only at the surface of thick biofilms, penetrating less than 20 μm after 1 h of exposure. The relatively slow movement of Zn into deeper biofilm layers provides direct evidence in support of the concept that thick biofilms may confer resistance to toxic metal species by binding metals at the biofilm-bulk liquid interface, thereby retarding metal diffusion into the biofilm (G. M. Teitzel and M. R. Park, Appl. Environ. Microbiol. 69:2313-2320, 2003).
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Kristich, Christopher J., Yung-Hua Li, Dennis G. Cvitkovitch, and Gary M. Dunny. "Esp-Independent Biofilm Formation by Enterococcus faecalis." Journal of Bacteriology 186, no. 1 (January 1, 2004): 154–63. http://dx.doi.org/10.1128/jb.186.1.154-163.2004.
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ABSTRACT Enterococcus faecalis is a gram-positive opportunistic pathogen known to form biofilms in vitro. In addition, this organism is often isolated from biofilms on the surfaces of various indwelling medical devices. However, the molecular mechanisms regulating biofilm formation in these clinical isolates are largely unknown. Recent work has suggested that a specific cell surface protein (Esp) of E. faecalis is critical for biofilm formation by this organism. However, in the same study, esp-deficient strains of E. faecalis were found to be capable of biofilm formation. To test the hypothesis that Esp is dispensable for biofilm formation by E. faecalis, we used microtiter plate assays and a chemostat-based biofilm fermentor assay to examine biofilm formation by genetically well-defined, non-Esp-expressing strains. Our results demonstrate that in vitro biofilm formation occurs, not only in the absence of esp, but also in the absence of the entire pathogenicity island that harbors the esp coding sequence. Using scanning electron microscopy to evaluate biofilms of E. faecalis OG1RF grown in the fermentor system, biofilm development was observed to progress through multiple stages, including attachment of individual cells to the substratum, microcolony formation, and maturation into complex multilayered structures apparently containing water channels. Microtiter plate biofilm analyses indicated that biofilm formation or maintenance was modulated by environmental conditions. Furthermore, our results demonstrate that expression of a secreted metalloprotease, GelE, enhances biofilm formation by E. faecalis. In summary, E. faecalis forms complex biofilms by a process that is sensitive to environmental conditions and does not require the Esp surface protein.
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Cerca, Nuno, Kimberly K. Jefferson, Rosario Oliveira, Gerald B. Pier, and Joana Azeredo. "Comparative Antibody-Mediated Phagocytosis of Staphylococcus epidermidis Cells Grown in a Biofilm or in the Planktonic State." Infection and Immunity 74, no. 8 (August 2006): 4849–55. http://dx.doi.org/10.1128/iai.00230-06.
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ABSTRACT Staphylococcus epidermidis is an important cause of nosocomial infections. Virulence is attributable to elaboration of biofilms on medical surfaces that protect the organisms from immune system clearance. Even though leukocytes can penetrate biofilms, they fail to phagocytose and kill bacteria. The properties that make biofilm bacteria resistant to the immune system are not well characterized. In order to better understand the mechanisms of resistance of bacteria in biofilms to the immune system, we evaluated antibody penetration throughout the biofilm and antibody-mediated phagocytic killing of planktonic versus biofilm cells of S. epidermidis by using a rabbit antibody to poly-N-acetylglucosamine (PNAG). These antibodies are opsonic and protect against infection with planktonic cells of PNAG-positive Staphylococcus aureus and S. epidermidis. Antibody to PNAG readily penetrated the biofilm and bound to the same areas in the biofilm as did wheat germ agglutinin, a lectin known to bind to components of staphylococcal biofilms. However, biofilm cells were more resistant to opsonic killing than their planktonic counterparts in spite of producing more PNAG per cell than planktonic cells. Biofilm extracts inhibited opsonic killing mediated by antibody to PNAG, suggesting that the PNAG antigen within the biofilm matrix prevents antibody binding close to the bacterial cell surface, which is needed for efficient opsonic killing. Increased resistance of biofilm cells to opsonic killing mediated by an otherwise protective antibody was due not to a biofilm-specific phenotype but rather to high levels of antigen within the biofilm that prevented bacterial opsonization by the antibody.