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At least 19 recordsLinked to original sources
PubMed2006

Chlorine resistance of Listeria monocytogenes biofilms and relationship to subtype, cell density, and planktonic cell chlorine resistance.

Strains of Listeria monocytogenes vary in their ability to produce biofilms. This research determined if cell density, planktonic chlorine resistance, or subtype are associated with the resistance of L. monocytogenes biofilms to chlorine. Thirteen strains of L. monocytogenes were selected for this research based on biofilm accumulation on stainless steel and rep-PCR subtyping. These strains were challenged with chlorine to determine the resistance of individual strains of L. monocytogenes. Planktonic cells were exposed to 20 to 80 ppm sodium hypochlorite in 20 ppm increments for 5 min in triplicate per replication, and the experiment was replicated three times. The number of tubes with surviving L. monocytogenes was recorded for each isolate at each level of chlorine. Biofilms of each strain were grown on stainless steel coupons. The biofilms were exposed 60 ppm of sodium hypochlorite. When in planktonic culture, four strains were able to survive exposure to 40 ppm of chlorine, whereas four strains were able to survive 80 ppm of chlorine in at least one of three tubes. The remaining five strains survived exposure to 60 ppm of chlorine. Biofilms of 11 strains survived exposure to 60 ppm of chlorine. No association of biofilm chlorine resistance and planktonic chlorine resistance was observed; however, biofilm chorine resistance was similar for strains of the same subtype. Biofilm cell density was not associated with chlorine resistance. In addition, biofilms that survived chlorine treatment exhibited different biofilm morphologies. These data suggest that chlorine resistance mechanisms of planktonic cells and biofilms differ, with planktonic chlorine resistance being more affected by inducible traits, and biofilm chlorine resistance being more affected by traits not determined in this study.

Biofilms↗
PubMed1964

KILLING OF CHLORINE-RESISTANT BACTERIA BY CHLORINE-BROMINE SOLUTIONS.

The disinfective power of chlorine, bromine, and mixtures of chlorine and bromine at different ratios was compared. The influence of pH was also studied. The experiments were carried out in "purified" water and in natural waters of swimming pools, river, and sea. In the presence of high amounts of nitrogenous growth-promoting material (at neutral pH), bromine was more effective than chlorine; in waters containing low amounts of nitrogenous growth-promoting material, chlorine was found superior. Mixtures of chlorine and bromine at various ratios were found to increase in effectiveness inversely to the percentage of hypobromite generated, down to 10 or 5%. Such effectiveness was found at pH levels of 5.4 to 8.6 in both purified and natural water containing high and low amounts of nitrogenous growth-promoting material. Therefore, the above mixtures seem of practical value for the disinfection of various natural waters. Escherichia coli isolated in the presence of chlorine, either from swimming pools or after deliberate exposure to the halogen, were shown to be chlorine-resistant mutants. Their resistance was maintained for at least nine passages in the absence of the disinfectant, which accounts for the number of passages tested. Chlorine-resistant mutants were not affected by bromine alone but did show a marked sensitivity to low concentrations of bromine active in the presence of chlorine. This was achieved by admixing small amounts of bromide to hypochlorite. A hypothetical model is presented to explain the synergistic sequential block by the two disinfectants. Some chlorine-resistant mutants were found to have changed into relatively slow-growing organisms with a changed phase-sensitivity pattern.

Bromides↗
PubMed1995

Phenotypic and genetic diversity of chlorine-resistant Methylobacterium strains isolated from various environments.

Strains of pink-pigmented facultative methylotrophs which were isolated previously from various environments and assigned tentatively to the genus Methylobacterium were characterized in comparison with authentic strains of previously known species of this genus. Most of the isolates derived from chlorinated water supplies exhibited resistance to chlorine, whereas 29 to 40% of the isolates from air, natural aquatic environments, and clinical materials were chlorine resistant. None of the tested authentic strains of Methylobacterium species obtained from culture collections exhibited chlorine resistance. Numerical analysis of phenotypic profiles showed that the test organisms tested were separated from each other except M. organophilum and M. rhodesianum. The chlorine-resistant isolates were randomly distributed among all clusters. The 16S ribosomal DNA (rDNA) sequence-based phylogenetic analyses showed that representatives of the isolates together with known Methylobacterium species formed a line of descent distinct from that of members of related genera in the alpha-2 subclass of the Proteobacteria and were divided into three subclusters within the Methylobacterium group. These results demonstrate that there is phenotypic and genetic diversity among chlorine-resistant Methylobacterium strains within the genus.

Bacterial Typing Techniques↗
PubMed1986

Virulence plasmid-associated adhesion of Escherichia coli and its significance for chlorine resistance.

Introduction of the ColV, I-K94 virulence plasmid into strains of Escherichia coli led (for four out of five strains tested) to a marked increase in the ability of organisms to adhere to glass beads. For strain 1829, the plasmid led to increased attachment to other materials including sand, agar, agarose, chitin and cellulose. The increased adhesion to glass beads was due to the presence of the plasmid and not to its introduction into a variant with altered adhesive properties. The plasmid-encoded VmpA protein did not appear to be necessary for the ColV, I-K94-promoted adhesion but adhesion was absolutely dependent on the presence of derepressed levels of transfer components in the ColV+ strains and partially dependent on the presence of colicin components. The extent of the plasmid-promoted adhesion was greatest for organisms grown at 30 degrees, 37 degrees or 42 decrees C and adhesion was almost abolished by growth at 21 degrees or 25 degrees C; this finding is in accord with transfer and colicin components being involved in adhesion. Of several other plasmids tested for their effects on adhesion, those with derepressed transfer properties showed a marked effect as did the RI resistance plasmid. Because of the ease of handling glass bead-attached organisms, such preparations were used as a model for studying the relevance of attachment to the resistance of E. coli to chlorination in the water purification process. Organisms of 1829 ColV, I-K94, attached to glass beads, were more resistant to damage and killing by chlorine than were unattached organisms. Three findings suggest that such chlorine resistance may be significant for survival during water chlorination. Firstly, ColV, I-K94+ bacteria became attached if incubated in sewage effluent with glass beads at 20 degrees C. Secondly, ColV+ organisms already attached to glass beads maintained their attachment during 24 h incubation in effluent at 20 degrees C and thirdly such effluent incubated organisms remained chlorine resistant provided that they retained their attachment.

Bacterial Adhesion↗
PubMed1999

Vibrio cholerae O1 El Tor: identification of a gene cluster required for the rugose colony type, exopolysaccharide production, chlorine resistance, and biofilm formation.

The rugose colony variant of Vibrio cholerae O1, biotype El Tor, is shown to produce an exopolysaccharide, EPSETr, that confers chlorine resistance and biofilm-forming capacity. EPSETr production requires a chromosomal locus, vps, that contains sequences homologous to carbohydrate biosynthesis genes of other bacterial species. Mutations within this locus yield chlorine-sensitive, smooth colony variants that are biofilm deficient. The biofilm-forming properties of EPSETr may enable the survival of V. cholerae O1 within environmental aquatic habitats between outbreaks of human disease.

Biofilms↗
PubMed1996

Vibrio cholerae O1 can assume a chlorine-resistant rugose survival form that is virulent for humans.

Vibrio cholerae can shift to a "rugose" colonial morphology associated with expression of an amorphous exopolysaccharide that promotes cell aggregation. Flow cytometric studies indicated that up to 3% of particles in rugose cultures represented aggregates of >5 bacterial cells. Rugose variants of our test strains displayed resistance to killing by chlorine, with viable cells persisting for >30 min in 2 mg/L free chlorine; strains also showed resistance to killing by complement-mediated serum bactericidal activity. Six volunteers fed 10(6) cfu of a rugose variant of V. cholerae O1 El Tor Inaba N16961 developed symptoms typical of cholera, with a mean diarrheal stool volume of 2.2 L (range, 1.4-4.3). Isolates recovered from the stool of infected volunteers retained the rugose phenotype. The data suggest that rugose strains cause human disease. The role of these strains in the epidemiology of cholera remains to be determined.

Adult↗
PubMed2001

Chlorine-susceptible and chlorine-resistant type 021N bacteria occurring in bulking activated sludges.

Two filamentous bacteria causing bulking in two activated sludges were examined. Investigations using morphological features, staining techniques, and fluorescent in situ hybridization identified both filaments as type 021N. However, an examination of the effect of chlorine on the sludges revealed a chlorine-susceptible type 021N in one sludge and a chlorine-resistant type 021N in the other.

Chlorine↗
PubMed1982

Chlorine resistance patterns of bacteria from two drinking water distribution systems.

The relative chlorine sensitivities of bacteria isolated from chlorinated and unchlorinated drinking water distribution systems were compared by two independent methods. One method measured the toxic effect of free chlorine on bacteria, whereas the other measured the effect of combined chlorine. Bacteria from the chlorinated system were more resistant to both the combined and free forms of chlorine than those from the unchlorinated system, suggesting that there may be selection for more chlorine-tolerant microorganisms in chlorinated waters. Bacteria retained on the surfaces of 2.0-microns Nuclepore membrane filters were significantly more resistant to free chlorine compared to the total microbial population recovered on 0.2-micron membrane filters, presumably because aggregated cells or bacteria attached to suspended particulate matter exhibit more resistance than unassociated microorganisms. In accordance with this hypothesis, scanning electron microscopy of suspended particulate matter from the water samples revealed the presence of attached bacteria. The most resistant microorganisms were able to survive a 2-min exposure to 10 mg of free chlorine per liter. These included gram-positive spore-forming bacilli, actinomycetes, and some micrococci. The most sensitive bacteria were readily killed by chlorine concentrations of 1.0 mg liter-1 or less, and included most gram-positive micrococci, Corynebacterium/Arthrobacter, Klebsiella, Pseudomonas/Alcaligenes, Flavobacterium/Moraxella, and Acinetobacter.

Bacteria↗
PubMed1985

Enhanced chlorine resistance of tap water-adapted Legionella pneumophila as compared with agar medium-passaged strains.

Previous studies have shown that bacteria maintained in a low-nutrient "natural" environment such as swimming pool water are much more resistant to disinfection by various chemical agents than strains maintained on rich media. In the present study a comparison was made of the chlorine (Cl2) susceptibility of hot-water tank isolates of Legionella pneumophila maintained in tap water and strains passaged on either nonselective buffered charcoal-yeast extract or selective differential glycine-vancomycin-polymyxin agar medium. Our earlier work has shown that environmental and clinical isolates of L. pneumophila maintained on agar medium are much more resistant to Cl2 than coliforms are. Under the present experimental conditions (21 degrees C, pH 7.6 to 8.0, and 0.25 mg of free residual Cl2 per liter, we found the tap water-maintained L. pneumophila strains to be even more resistant than the agar-passaged isolates. Under these conditions, 99% kill of tap water-maintained strains of L. pneumophila was usually achieved within 60 to 90 min compared with 10 min for agar-passaged strains. Samples from plumbing fixtures in a hospital yielded legionellae which were "super"-chlorine resistant when assayed under natural conditions. After one agar passage their resistance dropped to levels of comparable strains which had not been previously exposed to additional chlorination. These studies more closely approximate natural conditions than our previous work and show that tap water-maintained L. pneumophila is even more resistant to Cl2 than its already resistant agar medium-passaged counterpart.

Agar↗
PubMed1980

Chlorine resistance of poliovirus isolants recovered from drinking water.

Poliovirus 1 isolants were recovered from finished drinking water produced by a modern, well-operated water treatment plant. These waters contained free chlorine residuals in excess of 1 mg/liter. The chlorine inactivation of purified high-titer preparations of two such isolants was compared with the inactivation behavior of two stock strains of poliovirus 1, LSc and Mahoney. The surviving fraction of virus derived from the two natural isolants was shown to be orders of magnitude greater than that of the standard strains. These results raise the question whether indirect drinking water standards based on free chlorine residuals are adequate public health measures, or whether direct standards based on virus determinations might be necessary.

Chlorine↗
PubMed1998

Effects of starvation on physiological activity and chlorine disinfection resistance in Escherichia coli O157:H7.

Escherichia coli O157:H7 can persist for days to weeks in microcosms simulating natural conditions. In this study, we used a suite of fluorescent, in situ stains and probes to assess the influence of starvation on physiological activity based on membrane potential (rhodamine 123 assay), membrane integrity (LIVE/DEAD BacLight kit), respiratory activity (5-cyano-2,3-di-4-tolyl-tetrazolium chloride assay), intracellular esterase activity (ScanRDI assay), and 16S rRNA content. Growth-dependent assays were also used to assess substrate responsiveness (direct viable count [DVC] assay), ATP activity (MicroStar assay), and culturability (R2A agar assay). In addition, resistance to chlorine disinfection was assessed. After 14 days of starvation, the DVC values decreased, while the values in all other assays remained relatively constant and equivalent to each other. Chlorine resistance progressively increased through the starvation period. After 29 days of starvation, there was no significant difference in chlorine resistance between control cultures that had not been exposed to the disinfectant and cultures that had been exposed. This study demonstrates that E. coli O157:H7 adapts to starvation conditions by developing a chlorine resistance phenotype.

Bacteriological Techniques↗
PubMed2005

Biofilm formation by Escherichia coli O157:H7 on stainless steel: effect of exopolysaccharide and Curli production on its resistance to chlorine.

The resistance of Escherichia coli O157:H7 strains ATCC 43895-, 43895-EPS (an exopolysaccharide [EPS]-overproducing mutant), and ATCC 43895+ (a curli-producing mutant) to chlorine, a sanitizer commonly used in the food industry, was studied. Planktonic cells of strains 43895-EPS and/or ATCC 43895+ grown under conditions supporting EPS and curli production, respectively, showed the highest resistance to chlorine, indicating that EPS and curli afford protection. Planktonic cells (ca. 9 log(10) CFU/ml) of all strains, however, were killed within 10 min by treatment with 50 microg of chlorine/ml. Significantly lower numbers of strain 43895-EPS, compared to those of strain ATCC 43895-, attached to stainless steel coupons, but the growth rate of strain 43895-EPS on coupons was not significantly different from that of strain ATCC 43895-, indicating that EPS production did not affect cell growth during biofilm formation. Curli production did not affect the initial attachment of cells to coupons but did enhance biofilm production. The resistance of E. coli O157:H7 to chlorine increased significantly as cells formed biofilm on coupons; strain ATCC 43895+ was the most resistant. Population sizes of strains ATCC 43895+ and ATCC 43895- in biofilm formed at 12 degrees C were not significantly different, but cells of strain ATCC 43895+ showed significantly higher resistance than did cells of strain ATCC 43895-. These observations support the hypothesis that the production of EPS and curli increase the resistance of E. coli O157:H7 to chlorine.

Bacterial Adhesion↗
PubMed2026

Involvement of cross-genus phages in bacterial resistance to chlorine disinfection.

Chlorine disinfection resistance in pathogenic microorganisms poses severe environmental concerns and public health risks. While phages play critical roles in host adaptation to environmental stress, how poly-host phages contribute to bacterial resistance to chlorine disinfectants remains poorly understood. Here, we investigated shifts in the population dynamics, transcriptional profiles, and function potentials of cross-genus phage-bacterial communities under exposure to chlorine disinfectants in a continuously operated anaerobic-anoxic-oxic system over a 92-day period, using integrated metagenomic and metatranscriptomic approaches. In the presence and absence of chlorine disinfectants, the genomic abundance and diversity of phage and bacterial communities showed similar variation trends, and the community structures of both exhibited clear differences. A strong significant positive correlation was observed between phage and bacterial diversity under chlorine exposure (R&#x202f;=&#x202f;0.975, p&#x202f;=&#x202f;0.00,057), whereas no significant correlation was detected in the absence of chlorine disinfection (R&#x202f;=&#x202f;-0.314, p&#x202f;=&#x202f;0.613), suggesting that chlorine disinfectants may enhance phage-bacteria interactions. Host-associated phages exhibited high consistency with their corresponding putative hosts in terms of genomic abundance (M2&#x202f;=&#x202f;0.0945, p&#x202f;=&#x202f;0.001) and transcript abundance (M2&#x202f;=&#x202f;0.3668, p&#x202f;=&#x202f;0.001), and they were also significantly correlated with cross-genus phages in both genomic abundance (R&#x202f;=&#x202f;0.97, p&#x202f;<&#x202f;2.2e-16) and transcript abundance (R&#x202f;=&#x202f;0.83, p&#x202f;<&#x202f;2.2e-16), which collectively suggests the critical role of cross-genus phages in the resistance of microbial communities to chlorine disinfectants. Bipartite association network analysis shows that cross-genus phages carry highly homologous genes to their putative hosts and may be involved in the horizontal transfer of these genes among bacteria. These homologous genes are involved in DNA repair, redox balance regulation, environmental stress adaptation and efflux pump functions, suggesting a synergistic role between cross-genus phages and their putative hosts in chlorine resistance. Our findings reveal that cross-genus phages can contribute to the resistance of bacterial communities to chlorine disinfectants, providing the theoretical foundation for evaluating the role of poly-host phages in microbial communities.

Chlorine resistance↗
PubMed2006

Interaction between Mycobacterium avium subsp. paratuberculosis and environmental protozoa.

BACKGROUND: Interactions between Mycobacterium avium subsp. paratuberculosis (Map) and free-living protozoa in water are likely to occur in nature. The potential impact of ingestion of Map by two naturally occurring Acanthamoeba spp. on this pathogen's survival and chlorine resistance was investigated. RESULTS: Between 4.6 and 9.1% of spiked populations of three Map strains (NCTC 8578, B2 and ATCC 19698), which had been added at a multiplicity of infection of 10:1, were ingested by Acanthamoeba castellanii CCAP 1501/1B and A. polyphaga CCAP 1501/3B during co-culture for 3 h at 25 degrees C. Map cells were observed to be present within the vacuoles of the amoebae by acid-fast staining. During extended co-culture of Map NCTC 8578 at 25 degrees C for 24 d with both A. castellanii and A. polyphaga Map numbers did not change significantly during the first 7 days of incubation, however a 1-1.5 log10 increase in Map numbers was observed between days 7 and 24 within both Acanthamoeba spp. Ingested Map cells were shown to be more resistant to chlorine inactivation than free Map. Exposure to 2 mug/ml chlorine for 30 min resulted in a log10 reduction of 0.94 in ingested Map but a log10 reduction of 1.73 in free Map (p < 0.001). CONCLUSION: This study demonstrated that ingestion of Map by and survival and multiplication of Map within Acanthamoeba spp. is possible, and that Map cells ingested by amoebae are more resistant to inactivation by chlorine than free Map cells. These findings have implications with respect to the efficacy of chlorination applied to Map infected surface waters.

Acanthamoeba↗
PubMed1985

Relative resistance to chlorine of poliovirus and coxsackievirus isolates from environmental sources and drinking water.

Several poliovirus and coxsackievirus isolates from environmental sources were compared with laboratory strains to determine their rate of inactivation by chlorine. All viruses were tested for up to 1,000 min in the presence of an initial free residual chlorine level of ca. 0.4 mg/liter. Coxsackievirus B5 (CB-5) isolates were found to be more resistant to chlorine than coxsackievirus B4 (CB-4), followed by poliovirus 1, 2, and 3 in order of decreasing resistance to chlorine. Environmental isolates of CB-5 were more resistant than the laboratory strain tested, and for two strains 12 and 22% of the input virus was still infectious after 100 min in the presence of free residual chlorine. Although CB-4 isolates were less resistant to chlorine than CB-5 isolates, after 1,000 min of contact 0.01% of the input virus was still infectious. Except for CB-5 isolates, isolates from environmental sources did not appear to be more resistant to chlorine than laboratory strains. Viruses isolated at different phases during the preparation of drinking water were not more resistant to chlorine and must thus have been protected by other mechanisms.

Chlorine↗
PubMed1999

Escherichia coli resistance to chlorine and glutathione synthesis in response to oxygenation and starvation.

Reduced glutathione (GSH) levels and resistance to chlorine were measured for two isogenic Escherichia coli strains stressed by oxygenation and/or starvation. The E. coli mutant deficient in GSH was not more sensitive to the oxidant than its parent strain when the bacteria were cultured with a low oxygenation rate. Starvation or oxygenation increased the resistance of the parent strain to chlorine, while the resistance of the deficient strain remained unchanged.

Aerobiosis↗