45 results on '"LECHEVALLIER, M. W."'
Search Results
2. Aeromonas sobria in chlorinated drinking water supplies
- Author
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LeChevallier, M. W., Evans, T. M., Seidler, R. J., Daily, O. P., Merrell, B. R., Rollins, D. M., and Joseph, S. W.
- Published
- 1982
- Full Text
- View/download PDF
3. Health significance and occurrence of injured bacteria in drinking water
- Author
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McFeters, G. A, LeChevallier, M. W, Singh, A, and Kippin, J. S
- Subjects
Life Sciences (General) - Abstract
Enteropathogenic and indicator bacteria become injured in drinking water with exposure to sublethal levels of various biological, chemical and physical factors. One manifestation of this injury is the inability to grow and form colonies on selective media containing surfactants. The resulting underestimation of indicator bacteria can lead to a false estimation of water potability. m-T7 medium was developed specifically for the recovery of injured coliforms (both "total" and fecal) in drinking water. The m-T7 method was used to survey operating drinking water treatment and distribution systems for the presence of injured coliforms that were undetected with currently used media. The mean recovery with m-Endo LES medium was less than 1/100 ml while it ranged between 6 and 68/100ml with m-T7 agar. The majority of samples giving positive results with m-T7 medium yielded no detectable coliforms with m-Endo LES agar. Over 95% of the coliform bacteria in these samples were injured. Laboratory experiments were also done to ascribe the virulence of injured waterborne pathogens. Enteropathogens including Salmonella typhimurium, Yersinia enterocolitica and Shigella spp. required up to 20 times the chlorine levels to produce the same injury in enterotoxigenic Escherichia coli (ETEC) and nonpathogenic coliforms. Similar results were seen with Y. enterocolitica exposed to copper. The recovery of ETEC was followed by delayed enterotoxin production, both in vitro and in the gut of experimental animals. This indicates that injured waterborne enteropathogenic bacteria can be virulent.
- Published
- 1986
4. Chapter 11: Control, treatment and disinfection of Mycobacterium avium complex in drinking water.
- Author
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LeChevallier, M. W.
- Subjects
- *
MYCOBACTERIUM avium , *PATHOGENIC microorganisms , *DRINKING water , *INFECTIOUS disease transmission , *PUBLIC health - Abstract
Chapter 11 of the book "Pathogenic Mycobacteria in Water: A Guide to Public Health Consequences, Monitoring and Management" is presented. It highlights the three basic mechanisms which govern the occurrence of pathogenic microorganisms in treated drinking-water. It also explores the methods of removal of mycobacteria by water treatment process. It further discusses the control, treatment and disinfection of Mycobacterium avium complex in drinking water.
- Published
- 2004
5. Enteric Virus Infection Risk from Intrusion of Sewage into a Drinking Water Distribution Network.
- Author
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TEUNIS, P. F. M., XU, M., FLEMING, K. K., YANG, J., MOE, C. L., and LECHEVALLIER, M. W.
- Published
- 2010
- Full Text
- View/download PDF
6. Molecular techniques and data integration: investigating distribution system coliform events.
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Payne, S. J., Besner, M. C., Lavoie, J., Krentz, C., Truelstrup Hansen, L., Friedman, M., LeChevallier, M. W., Prévost, M., and Gagnon, G. A.
- Subjects
DRINKING water ,COLIFORMS ,RETROSPECTIVE studies ,DNA ,PHENOTYPES ,ENTEROBACTER ,CITROBACTER - Abstract
A retrospective analysis of coliform events in a drinking water distribution system was conducted. A total of 13 coliform isolates with specific geographic/sampling records were analysed using microbial source tracking (MST) to establish genetic (based on DNA) and phenotypic (based on substrate utilization) relatedness between isolates, and a data integration approach (geo-spatial and event analysis) to identify potential causes for their presence. Phenotypic analysis, using the APIw 20E system, identified two major genera: Enterobacter and Citrobacter, showing a high degree of phenotypic similarity within each species. However genotypic analysis (using pulsed field gel electrophoresis) of the Enterobacter and Citrobacter isolates demonstrated a wide genetic diversity within each species. The data integration approach revealed the probable causes for coliform events were the installation of new mains (8 samples) and rehabilitation of existing main (1 sample). The data integration and MST approach (genotyping) suggested that these coliform events were a result of sporadic intrusion from maintenance events and not chronic biofilm re-growth. The combination of MST and the data integration approach offers utilities a potentially powerful tool for the examination and determination of coliform occurrences in a distribution system. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
7. Benefits of employing a disinfectant residual in distribution systems
- Author
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LeChevallier, M. W.
- Abstract
Since the beginning of the 20th century, the widespread use of chlorine to disinfect drinking water has resulted in a dramatic decrease in water-related disease. Additional tools to disinfect water, including ozone, chlorine dioxide, chloramines, and even ultraviolet light further increase the arsenal available to combat pathogenic microbes, although their use lags far behind that for free chlorine. For many years the taste of chlorine in drinking water has been equated with the guarantee of its safety. The progress against waterborne disease, however, has not been without its downside as science recognize the concern of disinfection by-products (DBPs) and customers raise their expectations for water without chlorinous tastes or odors. Now, at the turn of the next millennium, consideration is being voiced to whetherit is time to abandon the use of chemical disinfectants altogether, at least in the water delivered to customers. It is the position of this paper that this approach is premature and that control of water quality is such that one can not guarantee that water distributed without a residual disinfectant isn't subject to recontamination or microbial degradation prior to the customer's tap. Rather than to abandon the approach (disinfection) that has led to such public health milestones, researchers should focus their efforts to make compatible the goal of residual disinfection without tastes, odors, and minimal DBP levels. [ABSTRACT FROM AUTHOR]
- Published
- 1998
8. Mechanisms of bacterial survival in chlorinated drinking water
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Lee, R. G., Cawthon, C. D., and Lechevallier, M. W.
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BACTERIA ,CHLORINATION ,DRINKING water - Published
- 1988
9. Factors influencing numbers of Mycobacterium avium, Mycobacterium intracellulare, and other Mycobacteria in drinking water distribution systems.
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Falkinham JO 3rd, Norton CD, and LeChevallier MW
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- Biofilms growth & development, Colony Count, Microbial, Mycobacterium classification, Mycobacterium avium isolation & purification, Water Purification methods, Mycobacterium isolation & purification, Mycobacterium avium Complex isolation & purification, Water Microbiology, Water Supply
- Abstract
Eight water distribution systems were sampled over an 18-month period (528 water and 55 biofilm samples) to measure the frequency of recovery and number of mycobacteria, particularly Mycobacterium avium and Mycobacterium intracellulare, in raw source waters before and after treatment and within the distribution system. The systems were chosen to assess the influence of source water, treatment, and assimilable organic carbon levels on mycobacterial numbers. Overall, mycobacterial recovery from the systems was low (15% of samples). Numbers of mycobacteria ranged from 10 to 700,000 CFU liter(-1). The number of M. avium in raw waters was correlated with turbidity. Water treatment substantially reduced the number of mycobacteria in raw waters by 2 to 4 log units. Mycobacterial numbers were substantially higher in the distribution system samples (average, 25,000-fold) than in those collected immediately downstream from the treatment facilities, indicating that mycobacteria grow in the distribution system. The increase in mycobacterial numbers was correlated with assimilable organic carbon and biodegradable organic carbon levels (r(2) = 0.65, P = 0.03). Although M. intracellulare was seldom recovered from water samples, it was frequently recovered (six of eight systems) in high numbers from biofilms (average, 600 CFU/cm(2)). Evidently, the ecological niches of M. avium and M. intracellulare are distinct.
- Published
- 2001
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10. Waterborne diseases.
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Hunter PR, Colford JM, LeChevallier MW, Binder S, and Berger PS
- Subjects
- Communicable Diseases etiology, Humans, Communicable Diseases epidemiology, Disease Outbreaks, Water Microbiology, Water Pollution, Water Supply
- Published
- 2001
- Full Text
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11. Chlorine, chloramine, chlorine dioxide, and ozone susceptibility of Mycobacterium avium.
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Taylor RH, Falkinham JO 3rd, Norton CD, and LeChevallier MW
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- Chloramines pharmacology, Chlorine pharmacology, Chlorine Compounds pharmacology, Culture Media, Humans, Microbial Sensitivity Tests, Mycobacterium avium Complex isolation & purification, Oxides pharmacology, Ozone pharmacology, Water, Water Microbiology, Water Supply, AIDS-Related Opportunistic Infections microbiology, Disinfectants pharmacology, Mycobacterium avium Complex drug effects, Mycobacterium avium Complex growth & development, Mycobacterium avium-intracellulare Infection microbiology
- Abstract
Environmental and patient isolates of Mycobacterium avium were resistant to chlorine, monochloramine, chlorine dioxide, and ozone. For chlorine, the product of the disinfectant concentration (in parts per million) and the time (in minutes) to 99.9% inactivation for five M. avium strains ranged from 51 to 204. Chlorine susceptibility of cells was the same in washed cultures containing aggregates and in reduced aggregate fractions lacking aggregates. Cells of the more slowly growing strains were more resistant to chlorine than were cells of the more rapidly growing strains. Water-grown cells were 10-fold more resistant than medium-grown cells. Disinfectant resistance may be one factor promoting the persistence of M. avium in drinking water.
- Published
- 2000
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12. A pilot study of bacteriological population changes through potable water treatment and distribution.
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Norton CD and LeChevallier MW
- Subjects
- Bacteria classification, Bacteria growth & development, Bacteriological Techniques, Iron, Pilot Projects, Polyvinyl Chloride, Bacteria isolation & purification, Biofilms growth & development, Water Microbiology, Water Purification, Water Supply
- Abstract
This pilot study compares the compositions of bacterial biofilms in pipe networks supplied with water containing either high levels of biodegradable organic matter (BOM) or low levels of BOM (conventionally or biologically treated, respectively). The Microbial Identification System for fatty acid analysis was utilized in this study to identify a large number of organisms (>1,400) to determine population changes in both conventionally and biologically treated water and biofilms. Data generated during this study indicated that suspended bacteria have little impact on biofilms, and despite treatment (conventional or biological), suspended microbial populations were similar following disinfection. Prechlorination with free chlorine resulted not only in reduced plate count values but also in a dramatic shift in the composition of the bacterial population to predominately gram-positive bacteria. Chlorination of biologically treated water produced the same shifts toward gram-positive bacteria. Removal of assimilable organic carbon by the biologically active filters slowed the rate of biofilm accumulation, but biofilm levels were similar to those found in conventionally treated water within several weeks. Iron pipes stimulated the rate of biofilm development, and bacterial levels on disinfected iron pipes exceeded those for chlorinated polyvinyl chloride pipes. The study showed that the iron pipe surface dramatically influenced the composition, activity, and disinfection resistance of biofilm bacteria.
- Published
- 2000
- Full Text
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13. Impacts of the reduction of nutrient levels on bacterial water quality in distribution systems.
- Author
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Volk CJ and LeChevallier MW
- Subjects
- Biodegradation, Environmental, Biofilms, Fresh Water, Hydrogen-Ion Concentration, Nephelometry and Turbidimetry, Quality Assurance, Health Care, United States, Bacteria isolation & purification, Organic Chemicals analysis, Water Microbiology, Water Supply analysis, Water Supply standards
- Abstract
This study evaluated the impacts of reducing nutrient levels on bacterial water quality in drinking water. Two American Water System facilities (sites NJ102a and IN610) with histories of coliform problems were involved, and each water utility received two pilot distribution systems (annular reactors). One reactor simulated the conventional treatment conditions (control), while the other reactor was used to assess the effect of biological filtration and subsequent reduced biodegradable organic matter levels on suspended (water column) and biofilm bacterial concentrations in the distribution systems. Biodegradable organic matter levels were reduced approximately by half after biological treatment. For site NJ102a, the geometric mean of the assimilable organic carbon concentrations was 217 microg/liter in the plant effluent and 91 microg/liter after biological filtration. For both sites, plant effluent biodegradable dissolved organic carbon levels averaged 0.45 mg/liter, versus 0.19 to 0.22 mg/liter following biological treatment. Biological treatment improved the stability of free chlorine residuals, while it had little effect on chloramine consumption patterns. High bacterial levels from the biological filters resulted in higher bacterial concentrations entering the test reactors than entering the control reactors. On average, biofilms in the model systems were reduced by 1 log unit (from 1.4 x 10(5) to 1.4 x 10(4) CFU/cm(2)) and 0.5-log unit (from 2.7 x 10(5) to 7.8 x 10(4) CFU/cm(2)) by biological treatment at sites NJ102a and IN610, respectively. Interestingly, it required several months of biological treatment before there was an observable impact on bacterial water quality in the system, suggesting that the effect of the treatment change was influenced by other factors (i.e., pipe conditions or disinfection, etc.).
- Published
- 1999
- Full Text
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14. Detection of infectious Cryptosporidium parvum oocysts in surface and filter backwash water samples by immunomagnetic separation and integrated cell culture-PCR.
- Author
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Di Giovanni GD, Hashemi FH, Shaw NJ, Abrams FA, LeChevallier MW, and Abbaszadegan M
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- Animals, Base Sequence, Cryptosporidium parvum genetics, DNA, Protozoan genetics, DNA, Protozoan isolation & purification, Fluorescent Antibody Technique, Humans, Immunomagnetic Separation, Molecular Sequence Data, Parasitology methods, Polymerase Chain Reaction, Sequence Homology, Nucleic Acid, United States, Water Supply, Cryptosporidium parvum isolation & purification, Water parasitology
- Abstract
A new strategy for the detection of infectious Cryptosporidium parvum oocysts in water samples, which combines immunomagnetic separation (IMS) for recovery of oocysts with in vitro cell culturing and PCR (CC-PCR), was field tested with a total of 122 raw source water samples and 121 filter backwash water grab samples obtained from 25 sites in the United States. In addition, samples were processed by Percoll-sucrose flotation and oocysts were detected by an immunofluorescence assay (IFA) as a baseline method. Samples of different water quality were seeded with viable C. parvum to evaluate oocyst recovery efficiencies and the performance of the CC-PCR protocol. Mean method oocyst recoveries, including concentration of seeded 10-liter samples, from raw water were 26.1% for IMS and 16.6% for flotation, while recoveries from seeded filter backwash water were 9.1 and 5.8%, respectively. There was full agreement between IFA oocyst counts of IMS-purified seeded samples and CC-PCR results. In natural samples, CC-PCR detected infectious C. parvum in 4.9% (6) of the raw water samples and 7.4% (9) of the filter backwash water samples, while IFA detected oocysts in 13.1% (16) of the raw water samples and 5.8% (7) of the filter backwash water samples. All CC-PCR products were confirmed by cloning and DNA sequence analysis and were greater than 98% homologous to the C. parvum KSU-1 hsp70 gene product. DNA sequence analysis also revealed reproducible nucleotide substitutions among the hsp70 fragments, suggesting that several different strains of infectious C. parvum were detected.
- Published
- 1999
- Full Text
- View/download PDF
15. Full-scale studies of factors related to coliform regrowth in drinking water.
- Author
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LeChevallier MW, Welch NJ, and Smith DB
- Subjects
- Data Collection, Disinfectants, Enterobacteriaceae growth & development, Filtration, Humans, North America, Rain, Sanitary Engineering, Temperature, Water Purification methods, Enterobacteriaceae isolation & purification, Water Microbiology, Water Supply
- Abstract
An 18-month survey of 31 water systems in North America was conducted to determine the factors that contribute to the occurrence of coliform bacteria in drinking water. The survey included analysis of assimilable organic carbon (AOC), coliforms, disinfectant residuals, and operational parameters. Coliform bacteria were detected in 27.8% of the 2-week sampling periods and were associated with the following factors: filtration, temperature, disinfectant type and disinfectant level, AOC level, corrosion control, and operational characteristics. Four systems in the study that used unfiltered surface water accounted for 26.6% of the total number of bacterial samples collected but 64.3% (1,013 of 1,576) of the positive coliform samples. The occurrence of coliform bacteria was significantly higher when water temperatures were > 15 degrees C. For filtered systems that used free chlorine, 0.97% of 33,196 samples contained coliform bacteria, while 0.51% of 35,159 samples from chloraminated systems contained coliform bacteria. The average density of coliform bacteria was 35 times higher in free-chlorinated systems than in chloraminated water (0.60 CFU/100 ml for free-chlorinated water compared with 0.017 CFU/100 ml for chloraminated water). Systems that maintained dead-end free chlorine levels of < 0.2 mg/liter or monochloramine levels of < 0.5 mg/liter had substantially more coliform occurrences than systems that maintained higher disinfectant residuals. Free-chlorinated systems with AOC levels greater than 100 micrograms/liter had 82% more coliform-positive samples and 19 times higher coliform levels than free-chlorinated systems with average AOC levels less than 99 micrograms/liter. Systems that maintained a phosphate-based corrosion inhibitor and limited the amount of unlined cast iron pipe had fewer coliform bacteria. Several operational characteristics of the treatment process or the distribution system were also associated with increased rates of coliform occurrence. The study concludes that the occurrence of coliform bacteria within a distribution system is dependent upon a complex interaction of chemical, physical, operational, and engineering parameters. No one factor could account for all of the coliform occurrences, and one must consider all of the parameters described above in devising a solution to the regrowth problem.
- Published
- 1996
- Full Text
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16. Evaluation of the immunofluorescence procedure for detection of Giardia cysts and Cryptosporidium oocysts in water.
- Author
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LeChevallier MW, Norton WD, Siegel JE, and Abbaszadegan M
- Subjects
- Animals, Centrifugation, Density Gradient, Evaluation Studies as Topic, Filtration instrumentation, Reproducibility of Results, Cryptosporidium isolation & purification, Fluorescent Antibody Technique statistics & numerical data, Giardia isolation & purification, Water parasitology
- Abstract
The accurate determination of the presence of Giardia cysts and Cryptosporidium oocysts in surface waters requires a reliable method for the detection and enumeration of these pathogenic organisms. Published methods have usually reported recovery efficiencies of less than 50% for both cysts and oocysts. Typically, the losses are greater for Cryptosporidium oocysts than they are for Giardia cysts. The purpose of this study was to examine procedures used for sample collection, elution, concentration, and clarification to determine when losses of cysts and oocysts occurred during processing. The results showed that major losses of cysts and oocysts occurred during centrifugation and clarification. Depending on the centrifugation force, oocyst losses of as high as 30% occurred for each centrifugation step. A 1.15-specific-gravity Percoll-sucrose gradient was needed to optimize recovery of oocysts from natural water samples. Minor improvements in the procedure could be accomplished by selecting a filter other than the recommended 1-micron-pore-size (nominal-porosity) polypropylene filter.
- Published
- 1995
- Full Text
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17. Development of a rapid assimilable organic carbon method for water.
- Author
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Lechevallier MW, Shaw NE, Kaplan LA, and Bott TL
- Abstract
A rapid method for measurement of assimilable organic carbon (AOC) is proposed. The time needed to perform the assay is reduced by increasing the incubation temperature and increasing the inoculum density. The ATP luciferin-luciferase method quickly enumerates the test organisms without the need for plate count media or dilution bottles. There was no significant difference between AOC values determined with strain P17 for the ATP and plate count procedures. For strain NOX, the plate count procedure underestimated bacterial levels in some samples. Comparison of AOC values obtained by the Belleville laboratory (by the ATP technique) and the Stroud Water Research Center (by plate counts) showed that values were significantly correlated and not significantly different. The study concludes that the rapid AOC method can quickly determine the bacterial growth potential of water within 2 to 4 days.
- Published
- 1993
- Full Text
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18. Giardia and Cryptosporidium spp. in filtered drinking water supplies.
- Author
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LeChevallier MW, Norton WD, and Lee RG
- Subjects
- Animals, Cryptosporidium growth & development, Disinfection standards, Filtration, Giardia growth & development, Giardiasis parasitology, Giardiasis prevention & control, Nephelometry and Turbidimetry, Particle Size, Cryptosporidium isolation & purification, Disinfection instrumentation, Giardia isolation & purification, Water Microbiology, Water Supply
- Abstract
Giardia and Cryptosporidium levels were determined by using a combined immunofluorescence test for filtered drinking water samples collected from 66 surface water treatment plants in 14 states and 1 Canadian province. Giardia cysts were detected in 17% of the 83 filtered water effluents. Cryptosporidium oocysts, were observed in 27% of the drinking water samples. Overall, cysts or oocysts were found in 39% of the treated effluent samples. Despite the frequent detection of parasites in drinking water, microscopic observations of the cysts and oocysts suggested that most of the organisms were nonviable. Compliance with the filtration criteria outlined by the Surface Water Treatment Rule of the U.S. Environmental Protection Agency did not ensure that treated water was free of cysts and oocysts. The average plant effluent turbidity for sites which were parasite positive was 0.19 nephelometric turbidity units. Of sites that were positive for Giardia or Cryptosporidium spp., 78% would have been able to meet the turbidity regulations of the Surface Water Temperature Rule. Evaluation of the data by using a risk assessment model developed for Giardia spp. showed that 24% of the utilities examined would not meet a 1/10,000 annual risk of Giardia infection. For cold water conditions (0.5 degree C), 46% of the plants would not achieve the 1/10,000 risk level.
- Published
- 1991
- Full Text
- View/download PDF
19. Occurrence of Giardia and Cryptosporidium spp. in surface water supplies.
- Author
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LeChevallier MW, Norton WD, and Lee RG
- Subjects
- Animals, Cryptosporidium growth & development, Giardia growth & development, United States, United States Environmental Protection Agency, Cryptosporidium isolation & purification, Giardia isolation & purification, Water Microbiology, Water Pollution, Water Supply standards
- Abstract
Giardia and Cryptosporidium levels were determined by using a combined immunofluorescence test for source waters of 66 surface water treatment plants in 14 states and 1 Canadian province. The results showed that cysts and oocysts were widely dispersed in the aquatic environment. Giardia spp. were detected in 81% of the raw water samples. Cryptosporidium spp. were found in 87% of the raw water locations. Overall, Giardia or Cryptosporidium spp. were detected in 97% of the raw water samples. Higher cyst and oocyst densities were associated with source waters receiving industrial or sewage effluents. Significant correlations were found between Giardia and Cryptosporidium densities and raw water quality parameters such as turbidity and total and fecal coliform levels. Statistical modeling suggests that cyst and oocyst densities could be predicted on the basis of watershed and water quality characteristics. The occurrence of high levels of Giardia cysts in raw water samples may require water utilities to apply treatment beyond that outlined in the Surface Water Treatment Rule of the U.S. Environmental Protection Agency.
- Published
- 1991
- Full Text
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20. Bacterial nutrients in drinking water.
- Author
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LeChevallier MW, Schulz W, and Lee RG
- Subjects
- Carbon metabolism, Enterobacteriaceae isolation & purification, Enterobacteriaceae metabolism, Models, Statistical, Rain, Temperature, Enterobacteriaceae growth & development, Water Microbiology, Water Supply
- Abstract
Regrowth of coliform bacteria in distribution systems has been a problem for a number of water utilities. Efforts to solve the regrowth problem have not been totally successful. The current project, which was conducted at the New Jersey American Water Co.-Swimming River Treatment Plant, showed that the occurrence of coliform bacteria in the distribution system could be associated with rainfall, water temperatures greater than 15 degrees C, total organic carbon levels greater than 2.4 mg/liter, and assimilable organic carbon levels greater than 50 micrograms of acetate carbon equivalents per liter. A multiple linear regression model based on free chlorine residuals present in dead-end sections of the distribution system and temperature predicted 83.8% of the heterotrophic plate count bacterial variation. To limit the growth of coliform bacteria in drinking water, the study concludes that assimilable organic carbon levels should be reduced to less than 50 micrograms/liter.
- Published
- 1991
- Full Text
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21. Evidence for the role of copper in the injury process of coliform bacteria in drinking water.
- Author
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Domek MJ, LeChevallier MW, Cameron SC, and McFeters GA
- Subjects
- Cadmium analysis, Copper analysis, Escherichia coli metabolism, Humans, Kinetics, Lead analysis, Oxygen Consumption drug effects, Water analysis, Copper toxicity, Enterobacteriaceae drug effects, Escherichia coli drug effects, Water Microbiology, Water Supply
- Abstract
Low levels of copper in chlorine-free distribution water caused injury of coliform populations. Monitoring of 44 drinking water samples indicated that 64% of the coliform population was injured. Physical and chemical parameters were measured, including three heavy metals (Cu, Cd, and Pb). Copper concentrations were important, ranging from 0.007 to 0.54 mg/liter. Statistical analyses of these factors were used to develop a model to predict coliform injury. The model predicted almost 90% injury with a copper concentration near the mean observed value (0.158 mg/liter) in distribution waters. Laboratory studies with copper concentrations of 0.025 and 0.050 mg/liter in an inorganic carbon buffer under controlled conditions of temperature and pH caused over 90% injury within 6 and 2 days, respectively. Studies of the metabolism of injured Escherichia coli cells indicated that the respiratory chain is at least one site of damage in injured cells.
- Published
- 1984
- Full Text
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22. Impact of verification media and resuscitation on accuracy of the membrane filter total coliform enumeration technique.
- Author
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Evans TM, Seidler RJ, and LeChevallier MW
- Subjects
- Aerobiosis, Culture Media, Filtration, Water Supply, Bacteriological Techniques, Enterobacteriaceae isolation & purification, Water Microbiology
- Abstract
Verification of membrane filter total coliform colonies was compared in lauryl tryptose broth, and m-LAC broth primary media and brilliant green-lactose-bile broth and EC broth secondary media. Verification in m-LAC broth yielded the greatest number of aerogenic isolates for both untreated surface water and drinking water samples. Verification in brilliant green-lactose-bile broth increased the number of false-negative reactions. At least 90% of the isolates aerogenic in primary verification media and anaerogenic in brilliant green-lactose-bile broth were representative of the coliform genera. The addition of a resuscitation step in the membrane filter technique did not yield greater numbers of verified coliforms per sample. Verification of both typical and atypical colonies in m-LAC broth resulted in a 10-fold increase in coliform numbers from untreated surface water. With drinking water, verification of both colony types resulted in an increase from less than 1 coliform per 100 ml to greater than 1/100 ml. A single-step verification in m-LAC broth is proposed as a more rapid and sensitive coliform verification procedure than the standard technique.
- Published
- 1981
- Full Text
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23. Factors contributing to the reduced invasiveness of chlorine-injured Yersinia enterocolitica.
- Author
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LeChevallier MW, Schiemann DA, and McFeters GA
- Subjects
- Bacterial Proteins biosynthesis, Cell Membrane metabolism, HeLa Cells, Humans, RNA, Bacterial biosynthesis, Virulence, Yersinia enterocolitica drug effects, Yersinia enterocolitica genetics, Yersinia enterocolitica metabolism, Yersinia enterocolitica ultrastructure, Chlorine pharmacology, Yersinia enterocolitica pathogenicity
- Abstract
The invasion of epithelial cells in vitro and in vivo by chlorine-injured Yersinia enterocolitica was assessed by direct microscopic observations. These experiments showed that injury by chlorine inhibited invasiveness of virulent Y. enterocolitica. Two requirements appeared to be necessary for invasiveness: the organism must be viable and metabolically active, and the organism must have certain surface components to initiate engulfment. Inhibition of RNA synthesis by rifampin and protein synthesis by chloramphenicol, tetracycline, and spectinomycin inhibited the invasiveness but not the attachment of Y. enterocolitica to epithelial cells. Membrane preparations from untreated and antimicrobial-agent-treated Y. enterocolitica blocked the invasiveness of virulent Y. enterocolitica, whereas membranes from chlorinated cells were unable to block invasiveness. Chlorine did not change the hydrophobicity or surface charge of injured Y. enterocolitica. The results indicate that invasion was more than simple association of the bacterium with the epithelial cell and involved a specific trigger to stimulate engulfment.
- Published
- 1987
- Full Text
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24. Staphylococcus aureus in rural drinking water.
- Author
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LeChevallier MW and Seidler RJ
- Subjects
- Enterobacteriaceae isolation & purification, Enterotoxins biosynthesis, Oregon, Staphylococcus aureus metabolism, Rural Population, Staphylococcus aureus isolation & purification, Water Microbiology, Water Pollution, Water Supply
- Abstract
Coagulase-positive Staphylococcus aureus was isolated from over 6% of 320 rural drinking water specimens. Well water was the most common source examined. The presence of S. aureus was not found to correlate with the presence of coliform bacteria. Strains of Staphylococcus that produced enterotoxin A were found in 40% of the samples containing S. aureus. Additional studies showed that faucet aerator screens were common sources of high cell densities of S. aureus.
- Published
- 1980
- Full Text
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25. Evaluation of m-T7 agar as a fecal coliform medium.
- Author
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LeChevallier MW, Jakanoski PE, Camper AK, and McFeters GA
- Subjects
- Agar, Culture Media, Enterobacteriaceae isolation & purification, Humans, Microbiological Techniques, Sewage, Temperature, Enterobacteriaceae growth & development, Feces microbiology
- Abstract
m-T7 agar, designed to improve recoveries of injured total coliforms, was evaluated for its effectiveness as a fecal coliform medium. The time and temperature of preincubation were found to be crucial to the optimal recovery of fetal coliforms. Isolation rates for fecal coliforms on m-T7 agar from sewage effluents were the highest when plates were preincubated at 37 degrees C for 8 h before transfer to 44.5 degrees C for 12 h. The medium was found to produce consistently higher fecal coliform counts than all the other methods tested. Recoveries were 3.1 times greater than the standard m-FC method and 1.7 times greater than the two-layer enrichment, temperature acclimation procedure. Verification rates for fecal coliforms isolated on m-T7 agar averaged 89.0%, whereas verification rates for m-FC agar averaged only 82.8%. Both media isolated similar fecal coliform populations. The advantages of a single medium, highly effective for the isolation of both total and fecal coliforms, are discussed.
- Published
- 1984
- Full Text
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26. Effect of turbidity on chlorination efficiency and bacterial persistence in drinking water.
- Author
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LeChevallier MW, Evans TM, and Seidler RJ
- Subjects
- Chlorine, Disinfection, Filtration, Nephelometry and Turbidimetry, Seasons, Enterobacteriaceae isolation & purification, Water Microbiology, Water Supply
- Abstract
To define interrelationships between elevated turbidities and the efficiency of chlorination in drinking water, experiments were performed to measure bacterial survival, chlorine demand, and interference with microbiological determinations. Experiments were conducted on the surface water supplies for communities which practice chlorination as the only treatment. Therefore, the conclusions of this study apply only to such systems. Results indicated that disinfection efficiency (log10 of the decrease in coliform numbers) was negatively correlated with turbidity and was influenced by season, chlorine demand of the samples, and the initial coliform level. Total organic carbon was found to be associated with turbidity and was shown to interfere with maintenance of a free chlorine residual by creating a chlorine demand. Interference with coliform detection in turbid waters could be demonstrated by the recovery of typical coliforms from apparently negative filters. The incidence of coliform masking in the membrane filter technique was found to increase as the turbidity of the chlorinated samples increased. the magnitude of coliform masking in the membrane filter technique increased from less than 1 coliform per 100 ml in water samples of less than 5 nephelometric turbidity units to greater than 1 coliform per 100 ml in water samples of greater than 5 nephelometric turbidity units. Statistical models were developed to predict the impact of turbidity on drinking water quality. The results justify maximum contaminant levels for turbidity in water entering a distribution system as stated in the National Primary Drinking Water Regulations of the Safe Drinking Water Act.
- Published
- 1981
- Full Text
- View/download PDF
27. Influence of diluents, media, and membrane filters on detection fo injured waterborne coliform bacteria.
- Author
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McFeters GA, Cameron SC, and LeChevallier MW
- Subjects
- Citrobacter isolation & purification, Culture Media, Enterobacter isolation & purification, Enterobacteriaceae physiology, Escherichia coli isolation & purification, Filtration instrumentation, Klebsiella pneumoniae isolation & purification, Enterobacteriaceae isolation & purification, Water Microbiology
- Abstract
Pure cultures of Escherichia coli, Klebsiella pneumoniae, Enterobacter aerogenes, and Citrobacter freundii were injured ( greater than 90%) in water from a dead-end section of the Bozeman, Montana, distribution system. The effects of the following laboratory variables on the enumeration efficiency of injured and undamaged control cells were examined: (i) diluent composition, temperature, and time of exposure; (ii) media, using various formulations employed in enumerating gram-negative bacteria; and (iii) surface pore morphology of membrane filters. The addition of peptone or milk solids to diluents and low temperature (4 degrees C) maximized the recovery of injured cells, but had little effect on undamaged cells. Control cells were recovered with high efficiencies on most media tested, but recoveries of injured cells ranged from 0 to near 100%. Most of the media commonly used in water analysis recovered less than 30% of injured cells. This was explained in part by the sensitivity of injured bacteria to deoxycholate concentrations greater than 0.01%, whereas control cells were unaffected by 0.1%. Membrane filter surface pore morphology (at 35 degrees C) had a negligible effect on total coliform recoveries. Recommendations are made regarding procedures to improve the recovery of injured coliforms by routine laboratory practices.
- Published
- 1982
- Full Text
- View/download PDF
28. Examination and characterization of distribution system biofilms.
- Author
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LeChevallier MW, Babcock TM, and Lee RG
- Subjects
- Bacteria ultrastructure, Bacteriocins analysis, Culture Media, Enterobacteriaceae ultrastructure, Microscopy, Electron, Scanning, Bacteria growth & development, Enterobacteriaceae growth & development, Water Microbiology, Water Supply
- Abstract
Investigations concerning the role of distribution system biofilms on water quality were conducted at a drinking water utility in New Jersey. The utility experienced long-term bacteriological problems in the distribution system, while treatment plant effluents were uniformly negative for coliform bacteria. Results of a monitoring program showed increased coliform levels as the water moved from the treatment plant through the distribution system. Increased coliform densities could not be accounted for by growth of the cells in the water column alone. Identification of coliform bacteria showed that species diversity increased as water flowed through the study area. All materials in the distribution system had high densities of heterotrophic plate count bacteria, while high levels of coliforms were detected only in iron tubercles. Coliform bacteria with the same biochemical profile were found both in distribution system biofilms and in the water column. Assimilable organic carbon determinations showed that carbon levels declined as water flowed through the study area. Maintenance of a 1.0-mg/liter free chlorine residual was insufficient to control coliform occurrences. Flushing and pigging the study area was not an effective control for coliform occurrences in that section. Because coliform bacteria growing in distribution system biofilms may mask the presence of indicator organisms resulting from a true breakdown of treatment barriers, the report recommends that efforts continue to find methods to control growth of coliform bacteria in pipeline biofilms.
- Published
- 1987
- Full Text
- View/download PDF
29. Disinfection of bacteria attached to granular activated carbon.
- Author
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LeChevallier MW, Hassenauer TS, Camper AK, and McFeters GA
- Subjects
- Adhesiveness, Bacteria ultrastructure, Chlorine pharmacology, Drug Resistance, Microbial, Microscopy, Electron, Scanning, Bacteria drug effects, Carbon, Disinfection methods, Sterilization methods, Water Microbiology, Water Supply standards
- Abstract
Heterotrophic plate count bacteria, coliform organisms, and pathogenic microorganisms attached to granular activated carbon particles were examined for their susceptibility to chlorine disinfection. When these bacteria were grown on carbon particles and then disinfected with 2.0 mg of chlorine per liter (1.4 to 1.6 mg of free chlorine residual per liter after 1 h) for 1 h, no significant decrease in viable counts was observed. Washed cells attached to the surface of granular activated carbon particles showed similar resistance to chlorine, but a progressive increase in sublethal injury was found. Observations made by scanning electron microscope indicated that granular activated carbon was colonized by bacteria which grow in cracks and crevices and are coated by an extracellular slime layer. These data suggest a possible mechanism by which treatment and disinfection barriers can be penetrated and pathogenic bacteria may enter drinking water supplies.
- Published
- 1984
- Full Text
- View/download PDF
30. Failure of the most-probable-number technique to detect coliforms in drinking water and raw water supplies.
- Author
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Evans TM, Waarvick CE, Seidler RJ, and LeChevallier MW
- Subjects
- Bacteriological Techniques, False Negative Reactions, Enterobacteriaceae isolation & purification, Water Microbiology, Water Supply
- Abstract
A procedure was developed to detect false-negative reactions (interference) in the standard most-probable-number (S-MPN) technique for coliform enumeration of untreated surface water and potable water supplies. This modified MPN (M-MPN) procedure allowed a quantitative assessment of the interference with coliform detection in untreated surface water and potable water supplies. Coliform interference was found to occur in the presumptive, confirmed, and completed tests of the S-MPN technique. When coliforms were present, interference with their detection occurred in over 80% of the samples. The inferior nature of the S-MPN was revealed by the 100% increase in the incidence of completed coliform-positive drinking water samples obtained with the M-MPN technique. The M-MPN procedure was also superior to the standard membrane filter technique. Eight different species of coliforms were recovered from false-negative tests, including Citrobacter, Enterobacter, Klebsiella, and Escherichia coli (in decreasing order of occurrence). The use of standard MPN techniques for monitoring potable water supplies may lead to a false security that the drinking water supply is potable, i.e., free from indicator bacteria.
- Published
- 1981
- Full Text
- View/download PDF
31. Inactivation of biofilm bacteria.
- Author
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LeChevallier MW, Cawthon CD, and Lee RG
- Subjects
- Bacteria growth & development, Chloramines pharmacology, Chlorides pharmacology, Chlorine pharmacology, Colony Count, Microbial, Copper pharmacology, Enterobacteriaceae drug effects, Enterobacteriaceae growth & development, Hydrogen-Ion Concentration, Hypochlorous Acid pharmacology, Oxides pharmacology, Zinc pharmacology, Bacteria drug effects, Chlorine Compounds, Disinfectants pharmacology, Water Microbiology
- Abstract
The current project was developed to examine inactivation of biofilm bacteria and to characterize the interaction of biocides with pipe surfaces. Unattached bacteria were quite susceptible to the variety of disinfectants tested. Viable bacterial counts were reduced 99% by exposure to 0.08 mg of hypochlorous acid (pH 7.0) per liter (1 to 2 degrees C) for 1 min. For monochloramine, 94 mg/liter was required to kill 99% of the bacteria within 1 min. These results were consistent with those found by other investigators. Biofilm bacteria grown on the surfaces of granular activated carbon particles, metal coupons, or glass microscope slides were 150 to more than 3,000 times more resistant to hypochlorous acid (free chlorine, pH 7.0) than were unattached cells. In contrast, resistance of biofilm bacteria to monochloramine disinfection ranged from 2- to 100-fold more than that of unattached cells. The results suggested that, relative to inactivation of unattached bacteria, monochloramine was better able to penetrate and kill biofilm bacteria than free chlorine. For free chlorine, the data indicated that transport of the disinfectant into the biofilm was a major rate-limiting factor. Because of this phenomenon, increasing the level of free chlorine did not increase disinfection efficiency. Experiments where equal weights of disinfectants were used suggested that the greater penetrating power of monochloramine compensated for its limited disinfection activity. These studies showed that monochloramine was as effective as free chlorine for inactivation of biofilm bacteria. The research provides important insights into strategies for control of biofilm bacteria.
- Published
- 1988
- Full Text
- View/download PDF
32. Bacterial contamination of drinking water supplies in a modern rural neighborhood.
- Author
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Lamka KG, LeChevallier MW, and Seidler RJ
- Subjects
- Bacteria isolation & purification, Enterobacteriaceae growth & development, Oregon, Seasons, Bacteria growth & development, Rural Population, Water Microbiology, Water Pollution, Water Supply
- Abstract
On six occasions during a 15-month period, the private well and spring water supplies in a modern rural neighborhood of 78 households were examined for total coliforms, fecal coliforms, Staphylococcus aureus, and standard plate count bacteria. More than one-third of the water supplies were unsatisfactory on at least one occasion as judged by standard plate counts over 10(3)/ml and the presence of coliforms, fecal coliforms, and/or S. aureus. Citrobacter freundii, Klebsiella pneumoniae, and Escherichia coli were the most frequently isolated total coliforms. At least 12 other genera of bacteria were identified from standard plate count agar. Coliform contamination was found to be higher after periods of rainfall, and high standard plate counts were more prevalent during warmer weather. These observations probably reflect leakage of surface water into improperly sealed wells or aquifer contamination during winter and the lack of chlorination to control microbial regrowth during the warm season. An inverse correlation was found between the presence of high standard plate counts and incidence of coliforms. Consumer education and at least a twice yearly monitoring of private water supplies (winter and summer) are suggested methods to signal that treatment may be necessary to reduce the risk of waterborne disease.
- Published
- 1980
- Full Text
- View/download PDF
33. Comparison of verification procedures for the membrane filter total coliform technique.
- Author
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LeChevallier MW, Cameron SC, and McFeters GA
- Subjects
- Montana, Ultrafiltration, Water Supply, Bacteriological Techniques, Enterobacteriaceae isolation & purification, Micropore Filters, Water Microbiology
- Abstract
Verification of membrane filter total coliform colonies from drinking water was increased 87% by testing for the presence of beta-galactosidase and cytochrome oxidase, compared with verification by determination of gas production in lauryl tryptose broth. Over 90% of the coliforms verified by testing for beta-galactosidase and cytochrome oxidase were representative of the typical coliform genera.
- Published
- 1983
- Full Text
- View/download PDF
34. New medium for improved recovery of coliform bacteria from drinking water.
- Author
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LeChevallier MW, Cameron SC, and McFeters GA
- Subjects
- Citrobacter isolation & purification, Culture Media, Enterobacter isolation & purification, Enterobacteriaceae growth & development, Escherichia coli isolation & purification, Indicators and Reagents, Klebsiella isolation & purification, Lactose metabolism, Enterobacteriaceae isolation & purification, Water Microbiology, Water Supply
- Abstract
A new membrane filter medium was developed for the improved recovery of injured coliforms from drinking water. The new medium, termed m-T7, consists of 5.0 g of Difco Proteose Peptone no. 3, 20 g of lactose, 3.0 g of yeast extract, 0.4 ml of Tergitol 7 (25% solution), 5.0 g of polyoxyethylene ether W-1, 0.1 g of bromthymol blue, 0.1 g of bromcresol purple, and 15 g of agar per liter of distilled water. Additional selectivity may be obtained by aseptically adding 0.1 microgram of penicillin G per ml to the medium after autoclaving. In laboratory studies, m-T7 agar recovered 86 to 99% more laboratory-injured coliforms than did m-Endo agar. m-T7 agar also recovered an average of 43% more verified coliforms from 67 surface and drinking water samples than did the standard m-Endo membrane filter technique. From drinking water, m-T7 agar recovered nearly three times more coliforms than did m-Endo agar. Less than 0.5% of the colonies on m-T7 agar gave false-negative reactions, whereas greater than 70% of the typical yellow colonies from m-T7 agar produced gas in lauryl tryptose broth. Most of the verified coliforms isolated on m-T7 agar belonged to one of the four common coliform genera: Escherichia, 17.6%; Klebsiella, 21.7%; Citrobacter, 17.3%; Enterobacter, 32.2%. The results demonstrate that m-T7 agar is superior to m-Endo agar, especially for the isolation of injured coliforms from drinking water.
- Published
- 1983
- Full Text
- View/download PDF
35. Enumeration of Enterobacter cloacae after chloramine exposure.
- Author
-
Watters SK, Pyle BH, LeChevallier MW, and McFeters GA
- Subjects
- Colony Count, Microbial, Culture Media, Enterobacter drug effects, Chloramines pharmacology, Chlorine pharmacology, Enterobacter growth & development, Enterobacteriaceae growth & development
- Abstract
Growth of Enterobacter cloacae on various media was compared after disinfection. This was done to examine the effects of monochloramine and chlorine on the enumeration of coliforms. The media used were TLY (nonselective; 5.5% tryptic soy broth, 0.3% yeast extract, 1.0% lactose, and 1.5% Bacto-Agar), m-T7 (selective; developed to recover injured coliforms), m-Endo (selective; contains sodium sulfite), TLYS (TLY with sodium sulfite), and m-T7S (m-T7 with sodium sulfite). Sodium sulfite in any medium improved the recovery of chloramine-treated E. cloacae. However, sodium sulfite in TLYS and m-T7S did not significantly improve the detection of chlorine-treated E. cloacae, and m-Endo was the least effective medium for recovering chlorinated bacteria. Differences in recovery of chlorine- and chloramine-treated E. cloacae are consistent with mechanistic differences between the disinfectants.
- Published
- 1989
- Full Text
- View/download PDF
36. Injured coliforms in drinking water.
- Author
-
McFeters GA, Kippin JS, and LeChevallier MW
- Subjects
- Bacteriological Techniques, Culture Media, Enterobacteriaceae isolation & purification, Water Microbiology, Water Supply standards
- Abstract
Coliforms were enumerated by using m-Endo agar LES and m-T7 agar in 102 routine samples of drinking water from three New England community water systems to investigate the occurrence and significance of injured coliforms. Samples included water collected immediately after conventional treatment, during the backwash cycle, at various points in the distribution system, and 1 week after the break and subsequent repair of a distribution main. Injured coliforms in these samples averaged greater than 95%. m-T7 agar yielded 8- to 38-fold more coliforms than did m-Endo agar LES. The geometric mean of coliforms recovered by m-Endo agar LES was less than 1 confirmed coliform per 100 ml, although m-T7 agar yielded 5.7 to 67.5 confirmed coliforms per 100 ml. In addition, the majority of these samples giving positive results on m-T7 agar produced no detectable counts on m-Endo agar LES. These findings indicated that coliforms were injured and largely undetected by use of accepted analytical media in the systems examined.
- Published
- 1986
- Full Text
- View/download PDF
37. Factors promoting survival of bacteria in chlorinated water supplies.
- Author
-
LeChevallier MW, Cawthon CD, and Lee RG
- Subjects
- Chloramines pharmacology, Culture Media, Klebsiella pneumoniae drug effects, Temperature, Time Factors, Chlorine pharmacology, Disinfection, Klebsiella pneumoniae growth & development, Sterilization, Water Microbiology, Water Supply standards
- Abstract
Results of our experiments showed that the attachment of bacteria to surfaces provided the greatest increase in disinfection resistance. Attachment of unencapsulated Klebsiella pneumoniae grown in medium with high levels of nutrients to glass microscope slides afforded the microorganisms as much as a 150-fold increase in disinfection resistance. Other mechanisms which increased disinfection resistance included the age of the biofilm, bacterial encapsulation, and previous growth conditions (e.g., growth medium and growth temperature). These factors increased resistance to chlorine from 2- to 10-fold. The choice of disinfectant residual was shown to influence the type of resistance mechanism observed. Disinfection by free chlorine was affected by surfaces, age of the biofilm, encapsulation, and nutrient effects. Disinfection by monochloramine, however, was only affected by surfaces. Importantly, results showed that these resistance mechanisms were multiplicative (i.e., the resistance provided by one mechanism could be multiplied by the resistance provided by a second mechanism).
- Published
- 1988
- Full Text
- View/download PDF
38. Enumeration and characterization of standard plate count bacteria in chlorinated and raw water supplies.
- Author
-
LeChevallier MW, Seidler RJ, and Evans TM
- Subjects
- Actinomycetaceae isolation & purification, Aeromonas isolation & purification, Bacteria classification, Bacteria isolation & purification, Chlorine, Enterobacteriaceae isolation & purification, Oregon, Water Microbiology, Water Supply
- Abstract
Nearly 700 standard plate count (SPC) bacteria were isolated from drinking water and untreated surface water and identified according to a scheme developed to permit the rapid, simple classification of microorganisms to genus, species, or group. Actinomycetes and Aeromonas species were the two most common groups of SPC bacteria in chlorinated distribution water. Aeromonas spp. and Enterobacter agglomerans were the two most common groups of SPC bacteria in raw water. Identification of bacterial populations before and after contact with chlorine (1 to 2 mg/liter) for 1 h revealed that chlorination selected for gram-positive bacteria. Water that contained high densities of bacteria known to be antagonistic to coliforms had low coliform isolation rates. The membrane filtration technique for enumerating SPC bacteria recovered significantly higher numbers (P < 0.001) than the standard pour plate technique.
- Published
- 1980
- Full Text
- View/download PDF
39. Reduced virulence of Yersinia enterocolitica by copper-induced injury.
- Author
-
Singh A, LeChevallier MW, and McFeters GA
- Subjects
- Animals, Cell Aggregation, Dose-Response Relationship, Drug, Lethal Dose 50, Liver metabolism, Liver microbiology, Mice, Time Factors, Virulence, Yersinia Infections microbiology, Yersinia enterocolitica drug effects, Copper pharmacology, Yersinia enterocolitica pathogenicity
- Abstract
A sublethal concentration of copper (0.75 mg/liter) caused substantial injury (87 to 95%) of Yersinia enterocolitica serotype O:8 cells in 72 h at 4 degrees C without producing extensive cell death. Copper-injured cells had a higher 50% lethal dose in mice (2,700 CFU) than uninjured cells (150 CFU). This reduced virulence correlated with more rapid clearance of the injured cells from the blood of mice after intravenous inoculation. A possible role of the liver in this process was shown by significant cell accumulation in mouse livers when copper-injured Y. enterocolitica cells were administered, compared with uninjured bacteria. In vitro studies with isolated mouse liver membranes showed higher titers of aggregation with copper-injured cells than control cells. The in vitro aggregation reaction and blood clearance activity in vivo were abolished by sugars that are known to interact with a hepatic lectin. Our data suggest that copper-induced injury reduces the virulence of Y. enterocolitica and that the liver may be involved in nonimmune rapid clearance of the injured cells, probably by interaction with a hepatic lectin(s).
- Published
- 1985
- Full Text
- View/download PDF
40. Sensitivity of genetically engineered organisms to selective media.
- Author
-
Lechevallier MW, Camper AK, Broadaway SC, Henson JM, and McFeters GA
- Subjects
- Culture Media, Escherichia coli genetics, Genetic Engineering, Genotype, Escherichia coli growth & development
- Abstract
Eighteen strains of Escherichia coli used in genetic studies were tested for their ability to grow on several selective media. Highest recoveries were obtained with m-T7 agar. The SOS system, particularly the recA gene, may play some role in the sensitivity of E. coli to selective agents. These results may be important in the selection of media used to detect genetically engineered organisms released into the environment.
- Published
- 1987
- Full Text
- View/download PDF
41. Growth and persistence of pathogens on granular activated carbon filters.
- Author
-
Camper AK, LeChevallier MW, Broadaway SC, and McFeters GA
- Subjects
- Carbon, Filtration, Kinetics, Escherichia coli growth & development, Salmonella typhimurium growth & development, Yersinia enterocolitica growth & development
- Abstract
Three enteric pathogens Yersinia enterocolitica O:8, Salmonella typhimurium, and enterotoxigenic Escherichia coli, were examined for their ability to colonize granular activated carbon (GAC) in pure cultures and in the presence of autochthonous river water organisms. All three organisms readily colonized sterile GAC and maintained populations of ca. 10(5) to 10(7) CFU g-1 for 14 days when suspended in sterile river water. Exposure of pathogen biofilms on GAC to unsterile river water resulted in a gradual decline in pathogens on the carbon (0.08 to 0.14 log day-1). When pathogens were introduced to sterile GAC in the presence of heterotrophic plate count organisms, they attached at levels similar to those in the pure cultures and then decreased (0.10 to 0.22 log day-1). When added with heterotrophic plate count bacteria to GAC supporting a mature biofilm of native river water bacteria, they attached at a lower level (1.0 X 10(4) to 4.6 X 10(4) CFU g-1) and decreased at a more rapid rate (0.11 to 0.70 log day-1).
- Published
- 1985
- Full Text
- View/download PDF
42. Changes in virulence of waterborne enteropathogens with chlorine injury.
- Author
-
LeChevallier MW, Singh A, Schiemann DA, and McFeters GA
- Subjects
- Animals, Cell Line, Dose-Response Relationship, Drug, Enterobacteriaceae drug effects, Escherichia coli cytology, Escherichia coli drug effects, Escherichia coli pathogenicity, HeLa Cells, Lethal Dose 50, Mice, Salmonella typhimurium cytology, Salmonella typhimurium drug effects, Salmonella typhimurium pathogenicity, Shigella drug effects, Shigella pathogenicity, Virulence, Yersinia enterocolitica cytology, Yersinia enterocolitica drug effects, Yersinia enterocolitica pathogenicity, Chlorine pharmacology, Enterobacteriaceae pathogenicity
- Abstract
We designed experiments to assess the effect of chlorine injury on the virulence of waterborne enteropathogens. Higher chlorine doses (0.9 to 1.5 mg/liter) were necessary to produce injured Yersinia enterocolitica, Salmonella typhimurium, and Shigella spp. than to produce injured enterotoxigenic Escherichia coli or coliform bacteria (0.25 to 0.5 mg/liter) in the test system used; 50% lethal dose experiments in which mice were used showed that injured Y. enterocolitica cells were 20 times less virulent than uninjured control cells (3,300 and 160 CFU, respectively). This decrease in virulence was not related to reduced attachment to Henle 407 intestinal epithelial cells, but could be related to a loss of HeLa cell invasiveness. In contrast, injured S. typhimurium and enterotoxigenic E. coli cells lost their ability to attach to Henle cells. These data show that some enteropathogens and coliform bacteria differ in their sensitivities to chlorine injury and that the virulence determinants affected by chlorine may vary from one pathogen to another.
- Published
- 1985
- Full Text
- View/download PDF
43. Interactions between heterotrophic plate count bacteria and coliform organisms.
- Author
-
LeChevallier MW and McFeters GA
- Subjects
- Bacteria growth & development, Bacteriological Techniques, Bacteria isolation & purification, Enterobacteriaceae isolation & purification, Water Microbiology
- Abstract
Studies were initiated to investigate the interactions between heterotrophic plate count bacteria and coliform organisms. We used spiked samples to show that heterotrophic plate count bacteria could reduce coliform densities by more than 3 logs within 8 days. Some heterotrophic plate count bacteria were able to cause injury to the coliform population. A significant correlation (r = 0.66; P less than 0.05) was observed between the initial level of heterotrophic plate count bacteria and the rate of coliform decline. Competition for limiting organic carbon was hypothesized to be responsible for the observed effects.
- Published
- 1985
- Full Text
- View/download PDF
44. Bacteria associated with granular activated carbon particles in drinking water.
- Author
-
Camper AK, LeChevallier MW, Broadaway SC, and McFeters GA
- Subjects
- Bacteria metabolism, Bacteria ultrastructure, Filtration, Microscopy, Electron, Scanning, Bacterial Adhesion, Carbon, Water Microbiology, Water Supply
- Abstract
A sampling protocol was developed to examine particles released from granular activated carbon filter beds. A gauze filter/Swinnex procedure was used to collect carbon fines from 201 granular activated carbon-treated drinking water samples over 12 months. Application of a homogenization procedure (developed previously) indicated that 41.4% of the water samples had heterotrophic plate count bacteria attached to carbon particles. With the enumeration procedures described, heterotrophic plate count bacteria were recovered at an average rate of 8.6 times higher than by conventional analyses. Over 17% of the samples contained carbon particles colonized with coliform bacteria as enumerated with modified most-probable-number and membrane filter techniques. In some instances coliform recoveries were 122 to 1,194 times higher than by standard procedures. Nearly 28% of the coliforms attached to these particles in drinking water exhibited the fecal biotype. Scanning electron micrographs of carbon fines from treated drinking water showed microcolonies of bacteria on particle surfaces. These data indicate that bacteria attached to carbon fines may be an important mechanism by which microorganisms penetrate treatment barriers and enter potable water supplies.
- Published
- 1986
- Full Text
- View/download PDF
45. Coliform species recovered from untreated surface water and drinking water by the membrane filter, standard, and modified most-probable-number techniques.
- Author
-
Evans TM, LeChevallier MW, Waarvick CE, and Seidler RJ
- Subjects
- Bacteriological Techniques, Citrobacter isolation & purification, Enterobacter isolation & purification, Escherichia coli isolation & purification, Klebsiella isolation & purification, Enterobacteriaceae isolation & purification, Water Microbiology, Water Supply
- Abstract
The species of total coliform bacteria isolated from drinking water and untreated surface water by the membrane filter (MF), the standard most-probable-number (S-MPN), and modified most-probable-number (M-MPN) techniques were compared. Each coliform detection technique selected for a different profile of coliform species from both types of water samples. The MF technique indicated that Citrobacter freundii was the most common coliform species in water samples. However, the fermentation tube techniques displayed selectivity towards the isolation of Escherichia coli and Klebsiella. The M-MPN technique selected for more C. freundii and Enterobacter spp. from untreated surface water samples and for more Enterobacter and Klebsiella spp. from drinking water samples than did the S-MPN technique. The lack of agreement between the number of coliforms detected in a water sample by the S-MPN, M-MPN, and MF techniques was a result of the selection for different coliform species by the various techniques.
- Published
- 1981
- Full Text
- View/download PDF
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