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Rodríguez-López, María Isabel, Vicente M. Gómez-López, Viktorija Lukseviciute y Zivile Luksiene. "Modeling the Inactivation and Possible Regrowth of Salmonella enterica Treated with Chlorophyllin-Chitosan and Visible Light". Food Technology and Biotechnology 58, n.º 1 (22 de abril de 2020): 64–70. http://dx.doi.org/10.17113/ftb.58.01.20.6374.
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The study focuses on predictive modelling of inactivation of Salmonella enterica after treatment with chlorophyllin-chitosan complex and visible light. Salmonella cells were incubated with chlorophyllin-chitosan complex (0.001 % chlorophyllin and 0.1 % chitosan) for different times (5-60 min) and then illuminated with visible light (λ=405 nm, He=38 J/cm2). Inactivation curves and post-treatment regrowth curves were built based on microbiological viability tests and data were fitted to ten inactivation and two regrowth models. The photoactivated complex reduced Salmonella population, which were unable to regrow. Weibull and Baranyi models were the best to describe the inactivation and regrowth kinetics respectively. In conclusion, data from the kinetic analysis and predictive modelling confirmed that photoactivated chlorophyllin-chitosan complex is a promising non-thermal approach for inactivation of Gram-negative pathogens, since no bacterial regrowth after treatment has been predicted.
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Burge, Wylie D., Nancy K. Enkiri y David Hussong. "Salmonella regrowth in compost as influenced by substrate (salmonella regrowth in compost)". Microbial Ecology 14, n.º 3 (noviembre de 1987): 243–53. http://dx.doi.org/10.1007/bf02012944.
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Gözen, İrep y Banu Örmeci. "Effect of daylight on regrowth of bacteria in anaerobically digested sludge". Water Science and Technology 62, n.º 2 (1 de julio de 2010): 364–69. http://dx.doi.org/10.2166/wst.2010.268.
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This study investigated the regrowth of total coliform, Salmonella, and Clostridium perfringens in anaerobically digested sludge after centrifuge dewatering in the presence and absence of daylight. Sludge cake and centrate samples were collected from a treatment plant, and half of the samples was stored in daylight and the other half was stored in dark for three weeks. The bacteria levels in the cake and centrate samples were measured periodically throughout the storage period, and all three bacteria showed substantial regrowth. Presence of daylight increased the regrowth of Salmonella both in sludge cake and centrate, and increased the regrowth of total coliform in centrate. Salmonella exhibited the highest regrowth rate in cake among the three bacteria tested both in the presence and absence of light. Daylight did not appear to have a significant impact on the regrowth of Clostridium perfringens in cake and centrate, and on the regrowth of total coliform in cake. This might, however, be caused by the masking effect of the higher initial numbers of these bacteria in the samples. There is need for more research to thoroughly understand the effect of daylight on the regrowth of sludge bacteria.
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Gerba, Charles P., Nohelia Castro-del Campo, John P. Brooks y Ian L. Pepper. "Exposure and risk assessment of Salmonella in recycled residuals". Water Science and Technology 57, n.º 7 (1 de abril de 2008): 1061–65. http://dx.doi.org/10.2166/wst.2008.235.
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The potential health effects of Salmonella found in wastewater residuals is dependent on the exposure of individuals to the organism. This paper provides a risk assessment for human infection from Salmonella due to direct contact with Class B biosolids, and from contact with Class A biosolids following regrowth of Salmonella. In addition, a risk assessment is provided for infection via airborne transport of bioaerosols from Class B biosolids and biosolids in which regrowth had occurred, to off-site communities. Results of the risk characterization imply that the risk of human infection from direct contact with Class B land applied residuals and subsequent ingestion is low. In contrast, the risk from direct contact with Class A residuals following regrowth is greater. Risks from airborne transport of Salmonella via bioaerosols away from a Class B land application site are also low. However, once again the risk from aerosols resulting from biosolids in which regrowth had occurred was greater. Based on these analyses, we conclude that it is highly unlikely that Salmonella infections will occur from land applied Class A or B residuals. However, risks become significant if Class A biosolids are stored anaerobically i.e. saturated, prior to land application.
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Eamens, G. J., A. M. Waldron y P. J. Nicholls. "Survival of pathogenic and indicator bacteria in biosolids applied to agricultural land". Soil Research 44, n.º 7 (2006): 647. http://dx.doi.org/10.1071/sr06015.
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Concentrations of surviving Escherichia coli, Clostridium perfringens, and Salmonella spp. were determined temporally in mechanically dewatered biosolids derived from anaerobic–mesophilic digestion and applied to agricultural land. Following applications in different seasons, repeated assessments of bacterial concentrations in biosolid clumps, using most-probable-number (MPN) techniques, found sustained high levels of these bacteria. Bacterial concentrations were often well above soil background levels at 6 months, and in some cases 11–12 months, after land application. Survival in surface-applied biosolids was similar to that for biosolids incorporated into the soil, and between application rates of 10 or 30 dry t/ha. Salmonella concentrations in applied biosolids were not predicted from, and could exceed those of, the indicator organism E. coli. Multiple plot analyses indicated regrowth of E. coli and Salmonella can occur within biosolids, up to several months after application. However, Salmonella serovars likely to pose a significant risk to animal health were not detected among isolates from the dewatered biosolids. Reduced accessibility for grazing livestock by soil incorporation, together with the time taken for normal pasture establishment practices, and the limited pathogenicity of the vast majority of salmonellae present in biosolids may significantly reduce the risk of spread of these organisms to the human food chain.
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AL-Gheethi, Adel A. S., I. Norli y Mohd Omar Ab Kadir. "Elimination of enteric indicators and pathogenic bacteria in secondary effluents and lake water by solar disinfection (SODIS)". Journal of Water Reuse and Desalination 3, n.º 1 (1 de marzo de 2013): 39–46. http://dx.doi.org/10.2166/wrd.2013.060.
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The reduction of enteric indicators (fecal coliforms (FC) and Enterococcus faecalis) and elimination of pathogenic bacteria (Salmonella spp. and Staphylococcus aureus) in the secondary effluents and lake water by solar disinfection (SODIS) was studied in this article. FC, E. faecalis, Salmonella spp. and S. aureus were isolated and enumerated using membrane filtration techniques after SODIS of samples inside transparent polyethylene terephthalate (PET) bottles for 1, 2, 3, 4, 5, 6, 7 and 8 h. The results show that SODIS can reduce numbers of FC, Salmonella spp. and S. aureus by more than 4 log10 colony forming units (CFU)/100 mL after 6 h. However, regrowth of these bacteria was observed after the incubation of the treated samples at 37 °C for 24 h, whereas SODIS for 8 h would eliminate pathogenic bacteria and no regrowth would be observed in these samples as determined by an absence and presence technique using enrichment medium. E. faecalis was not eliminated in the secondary effluents and lake water by SODIS, but this bacterium was reduced to less than detection limits (1 CFU/100 mL) when the treated secondary effluent samples were stored for 16 days at room temperature. The elimination of pathogenic bacteria and reduction of enteric indicators resulted in undetectable levels using SODIS for secondary effluents and lake water.
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Sidhu, J. "The role of indigenous microorganisms in suppression of salmonella regrowth in composted biosolids". Water Research 35, n.º 4 (marzo de 2001): 913–20. http://dx.doi.org/10.1016/s0043-1354(00)00352-3.
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Sidhu, J., R. A. Gibbs, G. E. Ho y I. Unkovich. "Selection of Salmonella Typhimurium as an indicator for pathogen regrowth potential in composted biosolids". Letters in Applied Microbiology 29, n.º 5 (noviembre de 1999): 303–7. http://dx.doi.org/10.1046/j.1365-2672.1999.00626.x.
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Peng, Linda X., Morgan Wallace, Bridget Andaloro, Dawn Fallon, Lois Fleck, Dan Delduco y George Tice. "Modification of the BAX® System PCR Assay for Detecting Salmonella in Beef, Produce, and Soy Protein Isolate". Journal of AOAC INTERNATIONAL 94, n.º 1 (1 de enero de 2011): 172–78. http://dx.doi.org/10.1093/jaoac/94.1.172.
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Abstract The BAX® System PCR assay for Salmonella detection in foods was previously validated as AOAC Research Institute (RI) Performance Tested MethodSM (PTM) 100201. New studies were conducted on beef and produce using the same media and protocol currently approved for the BAX System PCR assay for E. coli O157:H7 multiplex (MP). Additionally, soy protein isolate was tested for matrix extension using the U.S. Food and Drug Administration-Bacteriological Analytical Manual (FDA-BAM) enrichment protocols. The studies compared the BAX System method to the U.S. Department of Agriculture culture method for detecting Salmonella in beef and the FDA-BAM culture method for detecting Salmonella in produce and soy protein isolate. Method comparison studies on low-level inoculates showed that the BAX System assay for Salmonella performed as well as or better than the reference method for detecting Salmonella in beef and produce in 8–24 h enrichment when the BAX System E. coli O157:H7 MP media was used, and soy protein isolate in 20 h enrichment with lactose broth followed by 3 h regrowth in brain heart infusion broth. An inclusivity panel of 104 Salmonella strains with diverse serotypes was tested by the BAX System using the proprietary BAX System media and returned all positive results. Ruggedness factors involved in the enrichment phase were also evaluated by testing outside the specified parameters, and none of the factors examined affected the performance of the assay.
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Morishige, Yuta, Atsushi Koike, Ai Tamura-Ueyama y Fumio Amano. "Induction of Viable but Nonculturable Salmonella in Exponentially Grown Cells by Exposure to a Low-Humidity Environment and Their Resuscitation by Catalase". Journal of Food Protection 80, n.º 2 (24 de enero de 2017): 288–94. http://dx.doi.org/10.4315/0362-028x.jfp-16-183.
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ABSTRACTSalmonella is a major cause of foodborne disease that sometimes occurs in massive outbreaks around the world. This pathogen is tolerant of low-humidity conditions. We previously described a method for induction of viable but nonculturable (VBNC) Salmonella enterica serovar Enteritidis by treatment with hydrogen peroxide (H2O2) and subsequent resuscitation with 0.3 mM sodium pyruvate. Here, we report a new method for the induction of the VBNC state in Salmonella Enteritidis cells, one involving dehydration. Exposure of Salmonella Enteritidis cells to dehydration stress under poor nutritional conditions (0.9% [wt/vol] NaCl) and 10 to 20% relative humidity at room temperature decreased the presence of culturable population to 0.0067%, but respiratory and glucose uptake active populations were maintained at 0.46 and 1.12%, respectively, meaning that approximately 1% may have entered the VBNC state. Furthermore, these VBNC cells could be resuscitated to acquire culturability by incubation with catalase in M9 minimal medium without glucose in a manner dependent on the dose of catalase but not sodium pyruvate. These results suggest that a low-humidity environment could cause Salmonella Enteritidis cells to enter the VBNC state and the cells could then be resuscitated for growth by treatment with catalase, suggesting a potential risk of Salmonella Enteritidis to survive in low water activity foods in the VBNC state and to start regrowth for foodborne illness.
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ANDERSON, ROBIN C., YONG S. JUNG, CHRISTY E. OLIVER, SHANE M. HORROCKS, KENNETH J. GENOVESE, ROGER B. HARVEY, TODD R. CALLAWAY, THOMAS S. EDRINGTON y DAVID J. NISBET. "Effects of Nitrate or Nitro Supplementation, with or without Added Chlorate, on Salmonella enterica Serovar Typhimurium and Escherichia coli in Swine Feces†". Journal of Food Protection 70, n.º 2 (1 de febrero de 2007): 308–15. http://dx.doi.org/10.4315/0362-028x-70.2.308.
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The effects of coincubating the active agent of an experimental chlorate product with nitrate or select nitro compounds, possible inducers and competing substrates for the targeted respiratory nitrate reductase, on concentrations of experimentally inoculated Salmonella enterica serovar Typhimurium and indigenous Escherichia coli were determined. Studies were completed in swine fecal suspensions as a prelude to the administration of these inhibitors to pigs. Results confirmed the bactericidal effect of chlorate (5 to 10 mM) against these fecal enterobacteria, reducing (P < 0.05) concentrations by >2 log CFU ml−1after 3 to 6 h of incubation. An effect (P < 0.05) of pH was observed, with considerable regrowth of Salmonella and E. coli occurring after 24 h of incubation in suspensions buffered to pH 7.1 but not in suspensions buffered to pH 6.5 or 5.6. A 24-h coincubation of fecal suspensions with 5 to 10 mM chlorate and as little as 2.5 mM nitrate or 10 to 20 mM 2-nitro-1-propanol, 2-nitroethanol, and, sometimes, nitroethane decreased (P < 0.05) Salmonella but not necessarily E. coli concentrations. 2-Nitro-1-propanol and 2-nitroethanol exhibited inhibitory activity against Salmonella and E. coli by an undetermined mechanism, even in the absence of added chlorate.
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Rosu, Valentina y Kelly T. Hughes. "σ28-Dependent Transcription in Salmonella enterica Is Independent of Flagellar Shearing". Journal of Bacteriology 188, n.º 14 (15 de julio de 2006): 5196–203. http://dx.doi.org/10.1128/jb.00299-06.
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ABSTRACT The FlgM anti-σ28 factor is secreted in response to flagellar hook-basal body completion to allow σ28-dependent transcription of genes needed late in flagellar assembly, such as the flagellin structural gene, fliC. A long-standing hypothesis was that one role of FlgM secretion was to allow rapid expression of flagellin in response to shearing. We tested this hypothesis by following FlgM secretion and fliC transcription in response to flagellar shearing. Experiments showed that the level of FlgM inside the cell was unchanged after shearing whereas the extracellular FlgM levels increased in the growth medium as time passed. Identical results were obtained with cells that were not exposed to shear forces: internal FlgM levels remained constant while external FlgM levels rose with time at rates similar to those for the sheared culture. Consistent with this find, FlgM/σ28-dependent class 3 gene expression was unaffected by flagellar shearing but was affected by the growth phase of the cell. Regardless of exposure to shear forces, flagellar class 3 transcription rose sharply and then declined. These results demonstrate that flagellar regrowth following shearing is independent of FlgM secretion.
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Metaane, Selma, Véronique Monteil, Sophie Ayrault, Louise Bordier, Corinne Levi-Meyreuis y Françoise Norel. "The stress sigma factor σS/RpoS counteracts Fur repression of genes involved in iron and manganese metabolism and modulates the ionome of Salmonella enterica serovar Typhimurium". PLOS ONE 17, n.º 3 (31 de marzo de 2022): e0265511. http://dx.doi.org/10.1371/journal.pone.0265511.
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In many Gram-negative bacteria, the stress sigma factor of RNA polymerase, σS/RpoS, remodels global gene expression to reshape the physiology of quiescent cells and ensure their survival under non-optimal growth conditions. In the foodborne pathogen Salmonella enterica serovar Typhimurium, σS is also required for biofilm formation and virulence. We have previously identified sRNAs genes positively controlled by σS in Salmonella, including the two paralogous sRNA genes, ryhB1 and ryhB2/isrE. Expression of ryhB1 and ryhB2 is repressed by the ferric uptake regulator Fur when iron is available. In this study, we show that σS alleviates Fur-mediated repression of the ryhB genes and of additional Fur target genes. Moreover, σS induces transcription of the manganese transporter genes mntH and sitABCD and prevents their repression, not only by Fur, but also by the manganese-responsive regulator MntR. These findings prompted us to evaluate the impact of a ΔrpoS mutation on the Salmonella ionome. Inductively coupled plasma mass spectrometry analyses revealed a significant effect of the ΔrpoS mutation on the cellular concentration of manganese, magnesium, cobalt and potassium. In addition, transcriptional fusions in several genes involved in the transport of these ions were regulated by σS. This study suggests that σS controls fluxes of ions that might be important for the fitness of quiescent cells. Consistent with this hypothesis, the ΔrpoS mutation extended the lag phase of Salmonella grown in rich medium supplemented with the metal ion chelator EDTA, and this effect was abolished when magnesium, but not manganese or iron, was added back. These findings unravel the importance of σS and magnesium in the regrowth potential of quiescent cells.
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Mecha, Achisa C., Maurice S. Onyango, Aoyi Ochieng y Maggy NB Momba. "Modelling inactivation kinetics of waterborne pathogens in municipal wastewater using ozone". Environmental Engineering Research 25, n.º 6 (6 de diciembre de 2019): 890–97. http://dx.doi.org/10.4491/eer.2019.432.
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Microbial water pollution is a key concern leading to waterborne diseases. This study evaluated the disinfection of wastewater using ozonation. The following aspects were investigated: inactivation efficiency against <i>Escherichia coli, Salmonella</i> species, <i>Shigella</i> species, and <i>Vibrio cholerae</i>; modelling of inactivation kinetics using disinfection models; and evaluation of microbial regrowth studies. 99% bacterial inactivation was obtained within 15 min, irrespective of the water matrix, showing the strong oxidizing potential of ozone. The disinfection data were fitted into the log-linear and Weibull models. The survival curves were non-linear and fitted the Weibull model (fractional bias and normalized mean square error equal to 0.0), especially at high bacterial concentrations (10<sup>6</sup> CFU/mL). The inactivation occurred in two stages: an initial rapid stage (15 min) and a final slow stage exhibiting a tailing mechanism (15-45 min) probably as a result of the self-defence mechanisms adopted by the bacteria to limit oxidative stress. Considering the pattern of survival curves, no significant differences (<i>p</i> > 0.05) were observed among the four tested bacterial species; thus showing that ozone was effective against all the bacteria tested. There was minimal bacterial regrowth in the treated samples 24 h after ozone disinfection with reactivation values of 0-5% obtained.
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Liang, L., S. G. Goh, G. G. R. V. Vergara, H. M. Fang, S. Rezaeinejad, S. Y. Chang, S. Bayen et al. "Alternative Fecal Indicators and Their Empirical Relationships with Enteric Viruses, Salmonella enterica, and Pseudomonas aeruginosa in Surface Waters of a Tropical Urban Catchment". Applied and Environmental Microbiology 81, n.º 3 (21 de noviembre de 2014): 850–60. http://dx.doi.org/10.1128/aem.02670-14.
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ABSTRACTThe suitability of traditional microbial indicators (i.e.,Escherichia coliand enterococci) has been challenged due to the lack of correlation with pathogens and evidence of possible regrowth in the natural environment. In this study, the relationships between alternative microbial indicators of potential human fecal contamination (Bacteroides thetaiotaomicron,Methanobrevibacter smithii, human polyomaviruses [HPyVs], and F+ and somatic coliphages) and pathogens (Salmonellaspp.,Pseudomonas aeruginosa, rotavirus, astrovirus, norovirus GI, norovirus GII, and adenovirus) were compared with those of traditional microbial indicators, as well as environmental parameters (temperature, conductivity, salinity, pH, dissolved oxygen, total organic carbon, total suspended solids, turbidity, total nitrogen, and total phosphorus). Water samples were collected from surface waters of urban catchments in Singapore.SalmonellaandP. aeruginosahad significant positive correlations with most of the microbial indicators, especiallyE. coliand enterococci. Norovirus GII showed moderately strong positive correlations with most of the microbial indicators, except for HPyVs and coliphages. In general, high geometric means and significant correlations between human-specific markers and pathogens suggest the possibility of sewage contamination in some areas. The simultaneous detection of human-specific markers (i.e.,B. thetaiotaomicron,M. smithii, and HPyVs) withE. coliand enterococcus supports the likelihood of recent fecal contamination, since the human-specific markers are unable to regrow in natural surface waters. Multiple-linear-regression results further confirm that the inclusion ofM. smithiiand HPyVs, together with traditional indicators, would better predict the occurrence of pathogens. Further study is needed to determine the applicability of such models to different geographical locations and environmental conditions.
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Vogler, A. P., M. Homma, V. M. Irikura y R. M. Macnab. "Salmonella typhimurium mutants defective in flagellar filament regrowth and sequence similarity of FliI to F0F1, vacuolar, and archaebacterial ATPase subunits." Journal of Bacteriology 173, n.º 11 (1991): 3564–72. http://dx.doi.org/10.1128/jb.173.11.3564-3572.1991.
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BELETE, TAMRAT, ERIN CROWLEY, PATRICK BIRD, JOSEPH GENSIC y F. MORGAN WALLACE. "A Comparison of the BAX System Method to the U.S. Food and Drug Administration's Bacteriological Analytical Manual and International Organization for Standardization Reference Methods for the Detection of Salmonella in a Variety of Soy Ingredients". Journal of Food Protection 77, n.º 10 (1 de octubre de 2014): 1778–83. http://dx.doi.org/10.4315/0362-028x.jfp-14-063.
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The performances of two DuPont BAX System PCR assays for detecting Salmonella on a variety of low-moisture soy ingredients were evaluated against the U.S. Food and Drug Administration's Bacteriological Analytical Manual (FDA BAM) method or the International Organization for Standardization (ISO) 6579 reference method. These evaluations were conducted as a single laboratory validation at an ISO 17025 accredited third-party laboratory. Validations were conducted on five soy ingredients: isolated soy protein (ISP), soy fiber, fluid soy lecithin, deoiled soy lecithin, and soy nuggets, using a paired-study design. The ISP was analyzed as both 25- and 375-g composite test portions, whereas all other sample matrices were analyzed as 375-g composite test portions. To evaluate 25-g test portions of ISP, the test material was inoculated using Salmonella enterica subsp. enterica serovar Mbandaka (Q Laboratories isolate 11031.1). Salmonella enterica subsp. enterica serovar Tennessee (Q Laboratories isolate 11031.3) was used for all other trials. For each trial of the method comparison, 25 samples were analyzed for each matrix: 5 uninoculated controls and 20 samples inoculated at low levels (0.2 to 2 CFU per test portion) that were targeted to achieve fractionally positive results (25 to 75%). Using McNemar's chi-square analysis, no significant difference at P ≥ 0.05 (χ2 ≤ 3.84) was observed between the number of positives obtained by the BAX System and the reference methods for all five test matrices evaluated. These studies indicate that the BAX System PCR assays, in combination with the single buffered peptone water primary enrichment and subsequent brain heart infusion regrowth step, demonstrate equivalent sensitivity and robustness compared with the FDA BAM and ISO reference methods for both 25- and 375-g composite samples. Moreover, there was no observed reduction of sensitivity in the larger 375-g composite samples for all five matrices.
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Lefevre, F., J. M. Audic y F. Ferrand. "Peracetic Acid Disinfection of Secondary Effluents Discharged off Coastal Seawater". Water Science and Technology 25, n.º 12 (1 de junio de 1992): 155–64. http://dx.doi.org/10.2166/wst.1992.0347.
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Peracetic acid (PAA), a well known powerful antimicrobial agent in hospitals and in agribusiness (Fraser, 1986), has recently been used to disinfect urban effluents. It appears to be highly competitive against chlorine (Audic, 1990; Baldry, French, Slater and Desprez, 1990; Giodani, Iacoponi, Polidori, 1989), the most widely used disinfectant for sewage disposal. As PAA is a new biocide, not much quantitative data is available on its action against the faecal indicator bacteria and viruses. An on-site experimental study investigated the disinfectant action of PAA against these indicator bacteria and viruses as well as against Salmonella and enterovirus. To complete this study we will test its action on suspended solids to find out whether there is regrowth of the microorganisms after treatment. Multi-factor analysis in terms of criteria like inactivation efficiency, safety environmental impact, and cost will be used to compare PAA to chlorination and ozonation, the most commonly used techniques.
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Aguilar, P., B. Jiménez, C. Maya, T. Orta de Velasquez y V. Luna. "Disinfection of sludge with high pathogenic content using silver and other compounds". Water Science and Technology 54, n.º 5 (1 de septiembre de 2006): 179–87. http://dx.doi.org/10.2166/wst.2006.561.
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A physicochemical sludge with high microbial content (102–104 FPU/g TS bacteriophages, 106–107 MPN/g TS faecal coliforms, 104 MPN/g TS Salmonella spp., 104 MPN/g TS Shigella spp., 103 MPN/g TS Pseudomonas aeruginosa,102 MPN/g TS Vibrio cholerae, 102–103 cysts/g TS Giardia sp., 102–104 oocyts/g TS Cryptosporidium sp., 168–215 viable helminth ova/g TS) was disinfected using silver, silver-copper, and silver-copper plus a synergistic agent (SA). Twenty milligrams Ag/g TS inactivated 4.8 log of faecal coliforms in 1 h; however, 40 mg Ag/g TS are needed to reduce helminth ova viability from 84 to 38.4% in the same period of time. Combinations of Ag-Cu (60:600 mg Ag-Cu/g TS) and Ag-SA (60:24 mg Ag-SA/g TS) inactivated 7.8 log of faecal coliforms and around 90% of helminth ova in 60 min. To produce USEPA class A biosolids, 10:100:8 and 5:50:13.3 mg Ag-Cu-SA/gTS are needed. Bacterial regrowth was not observed for all conditions producing <1,000 MPN/gTS faecal coliforms, suggesting a residual disinfection effect. Recommended doses to produce class A biosolids inactivated 2–4 log of bacteriophages, 4 log of Salmonella spp., 4 log of Shigella spp., 3 log of Pseudomonas aeruginosa, 2 log of Vibrio cholerae, 87–99.9% of Giardia sp., and 75–99.9% of Cryptosporidium sp.
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Bosshard, Franziska, Michael Berney, Michael Scheifele, Hans-Ulrich Weilenmann y Thomas Egli. "Solar disinfection (SODIS) and subsequent dark storage of Salmonella typhimurium and Shigella flexneri monitored by flow cytometry". Microbiology 155, n.º 4 (1 de abril de 2009): 1310–17. http://dx.doi.org/10.1099/mic.0.024794-0.
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Pathogenic enteric bacteria are a major cause of drinking water related morbidity and mortality in developing countries. Solar disinfection (SODIS) is an effective means to fight this problem. In the present study, SODIS of two important enteric pathogens, Shigella flexneri and Salmonella typhimurium, was investigated with a variety of viability indicators including cellular ATP levels, efflux pump activity, glucose uptake ability, and polarization and integrity of the cytoplasmic membrane. The respiratory chain of enteric bacteria was identified to be a likely target of sunlight and UVA irradiation. Furthermore, during dark storage after irradiation, the physiological state of the bacterial cells continued to deteriorate even in the absence of irradiation: apparently the cells were unable to repair damage. This strongly suggests that for S. typhimurium and Sh. flexneri, a relatively small light dose is enough to irreversibly damage the cells and that storage of bottles after irradiation does not allow regrowth of inactivated bacterial cells. In addition, we show that light dose reciprocity is an important issue when using simulated sunlight. At high irradiation intensities (>700 W m−2) light dose reciprocity failed and resulted in an overestimation of the effect, whereas reciprocity applied well around natural sunlight intensity (<400 W m−2).
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Jiménez, B., A. Chávez, C. Maya y L. Jardines. "Removal of microorganisms in different stages of wastewater treatment for Mexico City". Water Science and Technology 43, n.º 10 (1 de mayo de 2001): 155–62. http://dx.doi.org/10.2166/wst.2001.0607.
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In this study the removal of a diversity of microorganisms during different stages of treatment was evaluated. The process scheme consisted of Advanced Primary Treatment (APT), sand filtration, and chlorine disinfection. During the first 2 stages, fecal coliforms were reduced from 1.24×109 to 1.2×108 MPN/100 mL and helminth ova were reduced to less than 1 ova/L. Nevertheless, to obtain an effluent water quality that meets the microbiological standards recommended by the World Health Organization (1989) and the Mexican norm for water destined for agricultural reuse it was necessary to disinfect the effluent with a chlorine dose of 12 mg/L for a 3 hour contact time. Under these conditions, fecal coliforms were reduced from 1.2×109 to 5.8×101 MPN/100 mL, Salmonella spp. from 5.0×108 MPN/100 mL to below the detection limit, Pseudomonas aeruginosa from 2.0×105 MPN/100 mL to below the detection limit, and protozoan cysts from 1052 to 31 cysts/L. Regrowth of bacteria was never observed during the 48 hours period following disinfection. The active chlorine was primarily in the form of chloramines thus reducing the formation of other potentially carcinogenic disinfection byproducts.
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Rouch, Duncan A., Tania Mondal, Sneha Pai, Florian Glauche, Vennessa A. Fleming, Nerida Thurbon, Judy Blackbeard, Stephen R. Smith y Margaret Deighton. "Microbial safety of air-dried and rewetted biosolids". Journal of Water and Health 9, n.º 2 (18 de abril de 2011): 403–14. http://dx.doi.org/10.2166/wh.2011.134.
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To assess microbial safety of treated sewage sludge (biosolids), we examined the inactivation of microbial indicators for potential bacterial, viral and protozoan pathogens. The levels of indicators were determined throughout the air-drying and storage phases of anaerobically digested sewage sludge. Samples were collected from two wastewater treatment plants (WWTPs) in Victoria, Australia. Established methods were applied for analysis of bacteria and coliphages, based on membrane filtration and layered plates, respectively. In the pan drying phase, the prevalence of Escherichia coli was reduced by >5 log10 compared with sludge entering the pan. Thus, after pan drying of 8-11 months at WWTP A and 15 months at WWTP B, the numbers of E. coli were reduced to below 102 cfu/g dry solids (DS). This level is acceptable for unrestricted use in agriculture in Australia (P1 treatment grade), the UK (enhanced treatment status) and the USA (Class A pathogen reduction). Coliphage numbers also decreased substantially during the air-drying phase, indicating that enteric viruses are also likely to be destroyed during this phase. Clostridium perfringens appeared to be an overly conservative indicator. Survival, but not regrowth, of E. coli or Salmonella was observed in rewetted biosolids (15–20% moisture content), after being seeded with these species, indicating a degree of safety of stored biosolids upon rewetting by rain.
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Sinton, Lester W., Robin R. Braithwaite, Carollyn H. Hall y Margaret L. Mackenzie. "Survival of Indicator and Pathogenic Bacteria in Bovine Feces on Pasture". Applied and Environmental Microbiology 73, n.º 24 (19 de octubre de 2007): 7917–25. http://dx.doi.org/10.1128/aem.01620-07.
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ABSTRACT The survival of enteric bacteria was measured in bovine feces on pasture. In each season, 11 cow pats were prepared from a mixture of fresh dairy cattle feces and sampled for up to 150 days. Four pats were analyzed for Escherichia coli, fecal streptococci, and enterococci, and four inoculated pats were analyzed for Campylobacter jejuni and Salmonella enterica. Two pats were placed on drainage collectors, and another pat was fitted with a temperature probe. In the first 1 to 3 weeks, there were increases (up to 1.5 orders of magnitude) in the counts of enterococci (in four seasons), E. coli (three seasons), fecal streptococci (three seasons), and S. enterica (two seasons), but there was no increase in the counts of C. jejuni. Thereafter, the counts decreased, giving an average ranking of the times necessary for 90% inactivation of C. jejuni (6.2 days from deposition) < fecal streptococci (35 days) < S. enterica (38 days) < E. coli (48 days) < enterococci (56 days). The pat temperature probably influenced bacterial growth, but the pattern of increases and decreases was primarily determined by desiccation; growth occurred when the water content was greater than 80%, but at a water content of 70 to 75% counts decreased. E. coli and enterococcus regrowth appeared to result from pat rehydration. Of 20 monthly leaching losses of E. coli, 16 were <10% of the total counts in the pat, and 12 were <1%. Drainage losses of C. jejuni (generally <1%) were detected for only 1 to 2 months. Although enterococci exhibited the best survival rate, higher final counts suggested that E. coli is the more practical indicator of bovine fecal pollution.
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Zaleski, Kathleen J., Karen L. Josephson, Charles P. Gerba y Ian L. Pepper. "Potential Regrowth and Recolonization of Salmonellae and Indicators in Biosolids and Biosolid-Amended Soil". Applied and Environmental Microbiology 71, n.º 7 (julio de 2005): 3701–8. http://dx.doi.org/10.1128/aem.71.7.3701-3708.2005.
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ABSTRACT This study evaluated the potential for conversion of Class B to Class A biosolids with respect to salmonellae and fecal coliforms during solar drying in concrete lined drying beds. Anaerobically (8% solids) and aerobically (2% solids) digested Class B biosolids were pumped into field-scale drying beds, and microbial populations and environmental conditions were monitored. Numbers of fecal coliforms and salmonellae decreased as temperature and rate of desiccation increased. After 3 to 4 weeks, Class A requirements were achieved in both biosolids for the pathogens and the indicators. However, following rainfall events, significant increase in numbers was observed for both fecal coliforms and salmonellae. In laboratory studies, regrowth of fecal coliforms was observed in both biosolids and biosolid-amended soil, but the regrowth of salmonellae observed in the concrete-lined drying beds did not occur. These laboratory studies demonstrated that pathogens decreased in numbers when soil was amended with biosolids. Based on serotyping, the increased numbers of salmonellae seen in the concrete lined drying beds following rainfall events was most likely due to recolonization due to contamination from fecal matter introduced by animals and not from regrowth of salmonellae indigenous to biosolids. Overall, we conclude that the use of concrete-lined beds created a situation in which moisture added as rainfall accumulated in the beds, promoting the growth of fecal coliforms and salmonellae added from external sources.
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Gibbs, R. A., C. J. Hu, G. E. Ho y I. Unkovich. "Regrowth of faecal coliforms and salmonellae in stored biosolids and soil amended with biosolids". Water Science and Technology 35, n.º 11-12 (1 de junio de 1997): 269–75. http://dx.doi.org/10.2166/wst.1997.0745.
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Stabilised wastewater sludge (biosolids) has beneficial re-use properties but these are limited by the presence of human pathogens. In this study soil amendment with biosolids and storage of biosolids prior to re-use were examined as disposal and treatment options. In a soil amendment trial biosolids were mixed with sandy soil and monitored for 37 weeks. In two storage trials biosolids were stored in piles 1m high and monitored for <60 weeks. Included in the monitoring programme were tests to determine the concentrations of faecal coliforms, faecal streptococci and salmonellae. In both the soil amendment trials and biosolids storage trials, concentrations of indicator organisms and salmonellae decreased through an extended hot, dry summer period. Although these organisms were not detected in the majority of samples taken during the summer, repopulation of faecal coliforms and salmonellae occurred in the trials following rainfall at the beginning of the winter. In the case of one of the storage trials repopulation occurred following a period of 50 weeks when salmonellae and faecal coliforms were not detected. When repopulation occurred, faecal coliform concentrations increased to higher than those at the beginning of the trials. These results suggest that faecal coliforms and salmonellae were at undetectable concentrations through the summer period but were able to grow when provided with favourable conditions. From this limited trial it was concluded that soil amended with biosolids could not be considered free from pathogens for at least one year following amendment.
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Grayer, Dannielle C. y Latania K. Logan. "1004. Cladophora in Lake Michigan May Serve as Important Reservoirs for Antibiotic-Resistant Bacteria". Open Forum Infectious Diseases 8, Supplement_1 (1 de noviembre de 2021): S592—S593. http://dx.doi.org/10.1093/ofid/ofab466.1198.
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Abstract Background Cladophora is a green algae, native to the Great Lakes, and found in large quantities along Lake Michigan shorelines. Previous studies have shown that Cladophora provide protection and nutrients for the Enterobacteriaceae (Ent) family, allowing persistence and regrowth. Chicago waterways harbor concerning antibiotic-resistant (AR) Ent, however the community reservoirs are unknown. Our primary objective was to assess whether Cladophora harbor AR Ent and to secondarily assess AR Ent in local beach waters where Cladophora are present. Figure 1. Map of Lake Michigan showing sites (S1-S3) where Cladophora samples were collected. NB, North Beach, Racine, Wisconsin; Michigan City, Indiana; PL, Portage Lakefront, Indiana Dunes National Park, Indiana. Figure 2. Map of Lake Michigan showing sites (S4-S7) where beach surface water samples were obtained. Montrose, Foster, 63rd St, & Calumet beaches in Chicago, Illinois. Methods Cladophora were processed from three Indiana Lake Michigan sites (S1 and S2; Fig 1) in 2002 and 2012 (S3; Fig 1) at the USGS Lake Michigan Ecological Research Station (Chesterton, IN). In 2015, surface water samples were obtained by the USGS at four Chicago beaches (S4-S7; Fig 2), which also amass Cladophora. Bacteria were isolated shortly after collection. In 2019-2020, Ent were cultivated and susceptibilities were performed at Rush. Results In 2002-2003 (S1 and S2), 160 E. coli were cultured from Cladophora. There was AR to multiple classes, highest overall in tetracyclines (7.5%, range 6.2%-18.7%), cefoxitin (8%), and cefazolin (5.6%). Resistance to cefuroxime was 0.6%. Four Salmonella isolates from 2012 (S3) were pan-susceptible, while two Citrobacter isolates were resistant to penicillins, 1st and 2nd generation cephalosporins, and cephamycins. Beach surface water samples from 2015 revealed more pronounced AR in E. coli (n=185) involving multiple classes, including highest in ampicillin (12.4%), tetracyclines (8.1%); piperacillin (7%); cefazolin (3.8%), cephamycins (3.2%) and amoxicillin-clavulanate (2.7%). Resistance to 3rd-generation cephalosporins, fluoroquinolones, trimethoprim/sulfamethoxazole ranged from 0.5-2%. AR Ent varied by beach site with highest percentages at S4, the only site with an associated dog beach. Conclusion These findings suggest that Cladophora in recreational waterways may serve as reservoirs for AR Ent. Differences in AR Ent at beach sites may reflect varying degrees of fecal contamination. Identifying community reservoirs is key to better understanding the acquisition of antibiotic resistant Ent among healthy populations and has long-term ecological and public health implications. Disclosures All Authors: No reported disclosures
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LAPIDOT, ANAT y SIMA YARON. "Transfer of Salmonella enterica Serovar Typhimurium from Contaminated Irrigation Water to Parsley Is Dependent on Curli and Cellulose, the Biofilm Matrix Components". Journal of Food Protection 72, n.º 3 (1 de marzo de 2009): 618–23. http://dx.doi.org/10.4315/0362-028x-72.3.618.
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Enteric pathogens can contaminate fresh produce, and this contaminated produce can be a significant potential source of human illness. The objective of this study was to determine a possible mode of transfer of Salmonella Typhimurium from contaminated irrigation water to mature parsley plants and to investigate the role of bacterial cellulose and curli. Parsley plants were drip irrigated with water containing green fluorescent protein–labeled Salmonella Typhimurium. Stems and leaves were harvested 1 day after the third irrigation and examined for the presence of Salmonella Typhimurium. Three weeks after harvesting, the presence of Salmonella was again confirmed in the regrown plants. During this period, bacterial numbers on leaves declined from 4.1 (±0.3) to 2.3 (±0.1) log CFU g−1 (P < 0.05). Numbers in the soil were constant (5 log CFU g−1). Results demonstrated the ability of Salmonella Typhimurium to transfer from irrigation water to the edible parts of the plants. Confocal laser scanning microscopic images revealed that Salmonella Typhimurium formed aggregates at a depth of 8 to 32 μm beneath the leaf surface. Penetration might be achieved through the roots or the phyllosphere. The importance of the bacterial cellulose and curli was determined by comparing the wild-type strain with its mutants, which lack the ability to synthesize cellulose and curli. Counts of the double mutant were 2-log higher in the soil but 1-log lower in the leaves (P < 0.05). Deletion of the agfBA gene (for curli) was more effective than deletion of bcsA (for cellulose). Thus, curli and cellulose play a role in the transfer or survival of Salmonella Typhimurium in the plant, as they do for plant pathogens.
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Mangalappalli-Illathu, Anil K. y Darren R. Korber. "Adaptive Resistance and Differential Protein Expression of Salmonella enterica Serovar Enteritidis Biofilms Exposed to Benzalkonium Chloride". Antimicrobial Agents and Chemotherapy 50, n.º 11 (28 de agosto de 2006): 3588–96. http://dx.doi.org/10.1128/aac.00573-06.
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ABSTRACT The development of adaptive resistance of Salmonella enterica serovar Enteritidis ATCC 4931 biofilms following exposure to benzalkonium chloride (BC) either continuously (1 μg ml−1) or intermittently (10 μg ml−1 for 10 min daily) was examined. Biofilms adapted to BC over a 144-h period could survive a normally lethal BC challenge (500 μg ml−1 for 10 min) and then regrow, as determined by increases in biofilm thickness, total biomass, and the ratio of the viable biomass to the nonviable biomass. Exposure of untreated control biofilms to the lethal BC challenge resulted in biofilm erosion and cell death. Proteins found to be up-regulated following BC adaptation were those involved in energy metabolism (TpiA and Eno), amino acid and protein biosynthesis (WrbA, TrxA, RplL, Tsf, Tuf, DsbA, and RpoZ), nutrient binding (FruB), adaptation (CspA), detoxification (Tpx, SodB, and a probable peroxidase), and degradation of 1,2-propanediol (PduJ and PduA). A putative universal stress protein (YnaF) was also found to be up-regulated. Proteins involved in proteolysis (DegQ), cell envelope formation (RfbH), adaptation (UspA), heat shock response (DnaK), and broad regulatory functions (Hns) were found to be down-regulated following adaptation. An overall increase in cellular protein biosynthesis was deduced from the significant up-regulation of ribosomal subunit proteins, translation elongation factors, and amino acid biosynthesis protein and down-regulation of serine endoprotease. The cold shock response, stress response, and detoxification are suggested to play roles in the adaptive resistance of Salmonella serovar Enteritidis biofilms to BC.
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Tannouri, Abdo, Ziad Rizk, Marina Al Daccache, Chantal Ghanem, Valérie Azzi, Rami Haddad, Richard G. Maroun, Zeina Hobaika, Rebecca Badra y Dominique Salameh. "Characterization of Antagonist Potential of Selected Compost Bacterial Isolates (CBI) against Plant and Human Pathogens". Agronomy 12, n.º 12 (27 de noviembre de 2022): 2977. http://dx.doi.org/10.3390/agronomy12122977.
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Several fecal and enteric pathogens are present within the primary organic raw materials that are introduced to compost piles. These pathogens may compete with the existing microbiota and limit their efficiency, yielding only partial decomposition of the final compost. These pathogens also affect the process kinetics and persist in the final compost or may even regrow as a result of the declining effect of indigenous antagonistic micro-organisms. In this work, 11 indigenous bacterial isolates were selected from compost piles that were constructed from different percentages of comingled primary organic raw materials. Enzymatic, biochemical, and genetic characterization profiling of these strains was fulfilled. The top hits supplied by GenBank proved the genetic diversity of these strains, which belonged to 6 different families. This diversity, applied also at enzymatic and biochemical levels, showed the different degradation patterns of amino acids, carbohydrates, hormones, and proteins. CBI2 has been shown to be the most active isolate in the degradation of the different types of hormones and proteins from dairy products but lacks the enzymes needed for the degradation of ammonia into nitrogen. The antagonistic potential of recuperated secondary metabolites proved the total inhibition of all strains against Fusarium oxysporum and no growth limitation against Botrytis cinerea. Only the secondary metabolites of CBI1, CBI5, and CBI9 isolates showed inhibitory activity against Salmonella Typhimurium and Escherichia coli, whereas only those of CBI6 and CBI8 inhibited the growth of Salmonella Typhimurium and Listeria monocytogenes accordingly. From that finding, these strains are considered pioneering, with high potential to ensure both the efficient degradation of organic matter and the elimination of existing pathogens when applied to compost piles.
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Verhougstraete, M. P., M. N. Byappanahalli, J. B. Rose y R. L. Whitman. "Cladophora in the Great Lakes: impacts on beach water quality and human health". Water Science and Technology 62, n.º 1 (1 de julio de 2010): 68–76. http://dx.doi.org/10.2166/wst.2010.230.
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Cladophora in the Great Lakes grows rapidly during the warm summer months, detaches, and becomes free-floating mats as a result of environmental conditions, eventually becoming stranded on recreational beaches. Cladophora provides protection and nutrients, which allow enteric bacteria such as Escherichia coli, enterococci, Shigella, Campylobacter, and Salmonella to persist and potentially regrow in the presence of the algae. As a result of wind and wave action, these microorganisms can detach and be released to surrounding waters and can influence water quality. Enteric bacterial pathogens have been detected in Cladophora mats; E. coli and enterococci may populate to become part of the naturalized microbiota in Cladophora; the high densities of these bacteria may affect water quality, resulting in unnecessary beach closures. The continued use of traditional fecal indicators at beaches with Cladophora presence is inadequate at accurately predicting the presence of fecal contamination. This paper offers a substantial review of available literature to improve the knowledge of Cladophora impacts on water quality, recreational water monitoring, fecal indicator bacteria and microorganisms, and public health and policy.
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Nale, Janet Y., Gurinder K. Vinner, Viviana C. Lopez, Anisha M. Thanki, Preeda Phothaworn, Parameth Thiennimitr, Angela Garcia et al. "An Optimized Bacteriophage Cocktail Can Effectively Control Salmonella in vitro and in Galleria mellonella". Frontiers in Microbiology 11 (21 de enero de 2021). http://dx.doi.org/10.3389/fmicb.2020.609955.
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Salmonella spp. is a leading cause of gastrointestinal enteritis in humans where it is largely contracted via contaminated poultry and pork. Phages can be used to control Salmonella infection in the animals, which could break the cycle of infection before the products are accessible for consumption. Here, the potential of 21 myoviruses and a siphovirus to eliminate Salmonella in vitro and in vivo was examined with the aim of developing a biocontrol strategy to curtail the infection in poultry and swine. Together, the phages targeted the twenty-three poultry and ten swine prevalent Salmonella serotype isolates tested. Although individual phages significantly reduced bacterial growth of representative isolates within 6 h post-infection, bacterial regrowth occurred 1 h later, indicating proliferation of resistant strains. To curtail bacteriophage resistance, a novel three-phage cocktail was developed in vitro, and further investigated in an optimized Galleria mellonella larva Salmonella infection model colonized with representative swine, chicken and laboratory strains. For all the strains examined, G. mellonella larvae given phages 2 h prior to bacterial exposure (prophylactic regimen) survived and Salmonella was undetectable 24 h post-phage treatment and throughout the experimental time (72 h). Administering phages with bacteria (co-infection), or 2 h post-bacterial exposure (remedial regimen) also improved survival (73–100% and 15–88%, respectively), but was less effective than prophylaxis application. These pre-livestock data support the future application of this cocktail for further development to effectively treat Salmonella infection in poultry and pigs. Future work will focus on cocktail formulation to ensure stability and incorporation into feeds and used to treat the infection in target animals.
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Lee, Seung-Jin, Elias Gebru Awji, Na-hye Park y Seung-Chun Park. "Using In Vitro Dynamic Models To Evaluate Fluoroquinolone Activity against Emergence of Resistant Salmonella enterica Serovar Typhimurium". Antimicrobial Agents and Chemotherapy 61, n.º 2 (28 de noviembre de 2016). http://dx.doi.org/10.1128/aac.01756-16.
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ABSTRACT The objectives of this study were to determine pharmacokinetic/pharmacodynamic (PK/PD) indices of fluoroquinolones that minimize the emergence of resistant Salmonella enterica serovar Typhimurium (S. Typhimurium) using in vitro dynamic models and to establish mechanisms of resistance. Three fluoroquinolones, difloxacin (DIF), enrofloxacin (ENR), and marbofloxacin (MAR), at five dose levels and 3 days of treatment were simulated. Bacterial killing-regrowth kinetics and emergence of resistant bacteria after antibacterial drug exposure were quantified. PK/PD indices associated with different levels of antibacterial activity were computed. Mechanisms of fluoroquinolone resistance were determined by analyzing target mutations in the quinolone resistance-determining regions (QRDRs) and by analyzing overexpression of efflux pumps. Maximum losses in susceptibility of fluoroquinolone-exposed S. Typhimurium occurred at a simulated AUC/MIC ratio (area under the concentration-time curve over 24 h in the steady state divided by the MIC) of 47 to 71. Target mutations in gyrA (S83F) and overexpression of acrAB-tolC contributed to decreased susceptibility in fluoroquinolone-exposed S. Typhimurium. The current data suggest AUC/MIC (AUC/mutant prevention concentration [MPC])-dependent selection of resistant mutants of S. Typhimurium, with AUC/MPC ratios of 69 (DIF), 62 (ENR), and 39 (MAR) being protective against selection of resistant mutants. These values could not be achieved in veterinary clinical areas under the current recommended therapeutic doses of the fluoroquinolones, suggesting the need to reassess the current dosing regimen to include both clinical efficacy and minimization of emergence of resistant bacteria.
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Ogunniyi, Abiodun D., Catherine E. Dandie, Sergio Ferro, Barbara Hall, Barbara Drigo, Gianluca Brunetti, Henrietta Venter et al. "Comparative antibacterial activities of neutral electrolyzed oxidizing water and other chlorine-based sanitizers". Scientific Reports 9, n.º 1 (diciembre de 2019). http://dx.doi.org/10.1038/s41598-019-56248-7.
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AbstractThere is increasing demand for safe and effective sanitizers for irrigation water disinfection to prevent transmission of foodborne pathogens to fresh produce. Here we compared the efficacy of pH-neutral electrolyzed oxidizing water (EOW), sodium hypochlorite (NaClO) and chlorine dioxide (ClO2) against single and mixed populations of E. coli, Listeria and Salmonella under a range of pH and organic matter content. EOW treatment of the mixed bacterial suspension resulted in a dose-dependent (<1 mg/L free chlorine), rapid (<2 min) and effective (4–6 Log10) reduction of the microbial load in water devoid of organic matter under the range of pH conditions tested (pH, 6.0, 7.0, 8.4 and 9.2). The efficacy of EOW containing 5 mg/L free chlorine was unaffected by increasing organic matter, and compared favourably with equivalent concentrations of NaClO and ClO2. EOW at 20 mg/L free chlorine was more effective than NaClO and ClO2 in reducing bacterial populations in the presence of high (20–100 mg/L) dissolved organic carbon, and no regrowth or metabolic activity was observed for EOW-treated bacteria at this concentration upon reculturing in rich media. Thus, EOW is as effective or more effective than other common chlorine-based sanitizers for pathogen reduction in contaminated water. EOW’s other characteristics, such as neutral pH and ease of handling, indicate its suitability for fresh produce sanitation.
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Harrand, Anna Sophia, Veronica Guariglia-Oropeza, Jordan Skeens, David Kent y Martin Wiedmann. "Nature versus Nurture: Assessing the impact of strain diversity and pre-growth conditions on Salmonella enterica, Escherichia coli, and Listeria spp. growth and survival on selected produce items". Applied and Environmental Microbiology, 4 de enero de 2021. http://dx.doi.org/10.1128/aem.01925-20.
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Inoculation studies are important when assessing microbial survival and growth in food products. These studies typically involve the pre-growth of multiple strains of a target pathogen under a single condition; this emphasizes strain diversity. To gain a better understanding of the impacts of strain diversity (“Nature”) and pre-growth conditions (“Nurture”) on subsequent bacterial growth in foods, we assessed the growth and survival of S. enterica (n=5), E. coli (n=6) and Listeria (n=5) inoculated onto tomatoes, pre-cut lettuce and cantaloupe rind, respectively. Pre-growth conditions included (i) 37°C to stationary phase (“baseline”) as well as (ii) low pH, (iii) high salt, (iv) reduced water activity, (v) log phase, (vi) minimal medium, and (vii) 21°C. Inoculated tomatoes were incubated at 21°C; lettuce and cantaloupe were incubated at 7°C. Bacterial counts were assessed over three phases, including initial reduction (“phase 1”), change in bacterial numbers over the first 24 h of incubation (“phase 2”), and change over the 7-day incubation (“phase 3”). E. coli showed overall decline in counts (<1 log) over the 7-day period, except for <1 log increase after pre-growth in high salt and to mid-log phase. In contrast, S. enterica and Listeria showed regrowth after an initial reduction. Pre-growth condition had a substantial and significant effect on all three phases of S. enterica and E. coli population dynamics on inoculated produce, whereas strain did not show a significant effect. For Listeria, both pre-growth condition and strain affected changes in phase 2, but not phases 1 and 3. IMPORTANCE Our findings suggest that inclusion of multiple pre-growth conditions in inoculation studies can best capture the range of growth and survival patterns expected for S. enterica and E. coli present on produce. This is particularly important for fresh and fresh-cut produce where stress conditions encountered by pathogens prior to contamination can vary widely, making selection of a "typical pre-growth condition" virtually impossible. Pathogen growth and survival data generated using multiple pre-growth conditions will allow for more robust microbial risk assessments that account more accurately for uncertainty.
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"Regrowth of faecal coliforms and salmonellae in stored biosolids and soil amended with biosolids". Water Science and Technology 35, n.º 11-12 (1997). http://dx.doi.org/10.1016/s0273-1223(97)00271-0.
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