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Biomedical subjects

D J Reasoner

Publications and source records attributed to D J Reasoner.

At least 19 recordsLinked to original sources
PubMed2003

Molecular characterization of bacteria inhabiting a water distribution system simulator.

The objective of this study was to monitor the impact of chlorination and chloramination treatments on heterotrophic bacteria (HB) and ammonia-oxidizing bacteria (AOB) inhabiting a water distribution system simulator. HB densities decreased while AOB densities increased when chloramine was added. AOB densities decreased below detection limits after the disinfection treatment was switched back to chlorination. The presence of AOB was confirmed using a group-specific 16S rDNA-PCR method. 16S rDNA sequence analysis showed that most bacterial isolates from feed water, discharge water, and biofilm samples were alpha-Proteobacteria or beta-Proteobacteria. The latter bacterial groups were also numerically dominant among the sequences recovered from water and biofilm 16S rDNA clone libraries. The relative frequency of each culturable bacterial group was different for each sample examined. Denaturing gradient gel electrophoresis analysis of total community 16S rDNA genes showed notable differences between the microbial community structure of biofilm samples and feed water. The results of this study suggest that disinfection treatments could influence the type of bacterial community inhabiting water distribution systems.

Ammonia↗
PubMed2001

Improving waterborne disease outbreak investigations.

This article is a summary of discussions held and recommendations made at a workshop for the investigation of waterborne disease outbreaks in Chapel Hill, North Carolina, December 7-8, 1998. Suspected waterborne outbreaks in the United States are primarily investigated by state and local public health officials who may infrequently conduct enteric disease outbreak investigations. Thus, it is important that officials have a formal plan to ensure that epidemiological studies are methodologically sound and that effective collaboration occurs among the epidemiologists, scientists, and engineers who will conduct the investigations. Laboratory support to analyze water samples and clinical specimens should be arranged well in advance of when services may be needed. Enhanced surveillance activities can help officials recognize additional outbreaks and initiate investigations in a timely manner. Epidemiologists should pay more attention early in the investigation to study design, questionnaire development, and sources of bias, especially recall bias, that may affect the interpretation of observed associations. Improved investigations can increase our knowledge about important etiological agents, water systems deficiencies, and sources of water contamination so that waterborne outbreaks can be more effectively prevented.

Data Collection↗
PubMed1997

Inactivation of Helicobacter pylori by chlorination.

Three strains of Helicobacter pylori were studied to determine their resistance to chlorination. The organisms were readily inactivated by free chlorine and should therefore be controlled by disinfection practices normally employed in the treatment of drinking water.

Chlorine↗
PubMed1996

Detection of Escherichia coli O157:H7 in water from coliform enrichment cultures.

Environmental water samples were seeded with Escherichia coli O157:H7 and the bacterium was recovered using a traditional coliform enrichment procedure followed by selective plating on sorbitol MacConkey agar and biochemical and serological characterization. Assays for beta-glucuronidase and glutamate decarboxylase were found to be useful procedures for screening suspected isolates. The organism was not recovered in a survey of various water samples.

Bacteriological Techniques↗
PubMed1995

Occurrence of high-level aminoglycoside resistance in environmental isolates of enterococci.

High-level resistance to aminoglycosides was observed in environmental isolates of enterococci. Various aquatic habitats, including agricultural runoff, creeks, rivers, wastewater, and wells, were analyzed. Strains of Enterococcus faecalis, E. faecium, E. gallinarum, and other Enterococcus spp. demonstrated multiple antibiotic resistance patterns to aminoglycosides.

Aminoglycosides↗
PubMed1993

Rapid glutamate decarboxylase assay for detection of Escherichia coli.

A rapid test procedure for the enzyme glutamate decarboxylase was developed for detection of Escherichia coli. The assay procedure was able to confirm the presence of E. coli in enteric broth cultures with 95% specificity for both pure cultures and environmental samples. The procedure was capable of detecting survivors among chlorine-exposed cells.

Bacteriological Techniques↗
PubMed1993

Evaluation and simplification of the assimilable organic carbon nutrient bioassay for bacterial growth in drinking water.

A modified assimilable organic carbon (AOC) bioassay is proposed. We evaluated all aspects of the AOC bioassay technique, including inoculum, incubation water, bioassay vessel, and enumeration technique. Other concerns included eliminating the need to prepare organic carbon-free glassware and minimizing the risks of bacterial and organic carbon contamination. Borosilicate vials (40 ml) with Teflon-lined silicone septa are acceptable incubation vessels. Precleaned vials are commercially available, and the inoculum can be injected directly through the septa. Both bioassay organisms, Pseudomonas fluorescens P-17 and Spirillum sp. strain NOX, are available from the American Type Culture Collection and grow well on R2A agar, making this a convenient plating medium. Turbid raw waters need to be filtered prior to an AOC analysis. Glass fiber filters used with either a peristaltic pump or a syringe-type filter holder are recommended for this purpose. A sampling design that emphasizes replication of the highest experimental level, individual batch cultures, is the most efficacious way to reduce the total variance associated with the AOC bioassay. Quality control for the AOC bioassay includes an AOC blank and checks for organic carbon limitation and inhibition of the bioassay organisms.

Bacteria↗
PubMed1989

Detection of fecal coliforms in water by using [14C]mannitol.

Interest in rapid bacterial detection methods for sanitary indicator bacteria in water prompted a study of the use of [U-14C]mannitol to detect fecal coliforms (FC). A simple method which used m-FC broth, membrane filtration, and two-temperature incubation (35 degrees C for 2 h followed by 44.5 degrees C for 2.5 h) was developed. [U-14C]mannitol was added to the medium, and the temperature was raised to 44.5 degrees C after 2 h at 35 degrees C. 14CO2 was collected as Ba14CO3 and assayed by liquid scintillation spectroscopy. Correlations were examined between FC cell numbers at the start of incubation (standard 24-h FC test) and Ba14CO3 counts per minute after 4.5 h. Results indicated that FC numbers ranging from 1 x 10(1) to 2.1 x 10(5) cells could be detected in 4.5 h. Within-sample reproducibility at all cell concentrations was good, but sample-to-sample reproducibility was variable. Comparisons between m-FC broth and m-FC broth modified by substituting D-mannitol for lactose indicated that the standard m-FC broth was the better test medium. Results from experiments in which dimethyl sulfoxide was used to increase permeability of FC to [U-14C]mannitol indicated no increase in 14CO2 production due to dimethyl sulfoxide. Detection of FC by this method may be useful for rapid estimation of FC levels in freshwater recreational areas, for estimating the quality of potable source water, and potentially for emergency testing of potable water, suspected of contamination due to distribution line breaks or cross-connections.

Carbon Dioxide↗
PubMed1989

Nonphotosynthetic pigmented bacteria in a potable water treatment and distribution system.

The occurrence of pigmented bacteria in potable water, from raw source water through treatment to distribution water, including dead-end locations, was compared at sample sites in a large municipal water system. Media used to enumerate heterotrophic bacteria and differentiate pigmented colonies were standard method plate count (SPC), m-SPC, and R2A agars, incubated up to 7 days at 35 degrees C. The predominant pigmented bacteria at most sample locations were yellow and orange, with a small incidence of pink organisms at the flowing distribution site. Seasonal variations were seen, with the yellow and orange organisms shifting in dominance. SPC agar was the least productive medium for both heterotroph counts and pigmented bacteria differentiation. At the flowing distribution site, percentages of pigmented bacteria on SPC medium ranged from 2.3 to 9.67 times less than on m-SPC and from 2.3 to 9.86 times less than on R2A. At the same site, seasonal trends in the percentage of pigmented bacteria were the same for m-SPC and R2A media, and the highest and lowest percentages occurred in the fall and winter, respectively. At site 6, there appeared to be an inverse relationship between the yellow and orange pigmented groups, but upon analysis, this did not hold and all correlations between yellow and orange pigmented bacteria were positive. The study results indicate that pigmented bacteria could readily be detected by using plate counting media developed for heterotroph enumeration in potable waters with incubation periods of 7 days. Pigmented bacteria can be used as an additional marker for monitoring changes in water quality. High numbers of heterotrophs, including pigmented forms, were found at dead-end locations, usually in the absence of a free chlorine residual and when the water temperature was greater than 16 degrees C. The association of some pigmented bacteria with nosocomial and other infections raises concern that the organisms may have originated from the potable water supply. High levels of pigmented bacteria could pose an increased health risk to immunologically compromised individuals. Therefore, the bacterial quality of the distribution water should be controlled to prevent the development of high concentrations of heterotrophic plate count bacteria, including the pigmented forms.

Analysis of Variance↗
PubMed1985

A new medium for the enumeration and subculture of bacteria from potable water.

Plate count agar is presently the recommended medium for the standard bacterial plate count (35 degrees C, 48-h incubation) of water and wastewater. However, plate count agar does not permit the growth of many bacteria that may be present in treated potable water supplies. A new medium was developed for use in heterotrophic plate count analyses and for subculture of bacteria isolated from potable water samples. The new medium, designated R2A, contains 0.5 g of yeast extract, 0.5 g of Difco Proteose Peptone no. 3 (Difco Laboratories), 0.5 g of Casamino Acids (Difco), 0.5 g of glucose, 0.5 g of soluble starch, 0.3 g of K2HPO4, 0.05 g of MgSO4 X 7H2O, 0.3 g of sodium pyruvate, and 15 g of agar per liter of laboratory quality water. Adjust the pH to 7.2 with crystalline K2HPO4 or KH2PO4 and sterilize at 121 degrees C for 15 min. Results from parallel studies with spread, membrane filter, and pour plate procedures showed that R2A medium yielded significantly higher bacterial counts than did plate count agar. Studies of the effect of incubation temperature showed that the magnitude of the count was inversely proportional to the incubation temperature. Longer incubation time, up to 14 days, yielded higher counts and increased detection of pigmented bacteria. Maximal bacterial counts were obtained after incubation at 20 degrees C for 14 days. As a tool to monitor heterotrophic bacterial populations in water treatment processes and in treated distribution water, R2A spread or membrane filter plates incubated at 28 degrees C for 5 to 7 days is recommended.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗
PubMed1979

Rapid seven-hour fecal coliform test.

A rapid 7-h fecal coliform (FC) test for the detection of FC in water has been developed. This membrane filter test utilizes a lightly buffered lactose-based medium (m-7-h FC medium) combined with a sensitive pH indicator system. FC colonies appeared yellow against a light purple background after incubation at 41.5 degrees C for 7 to 7.25 h. Comparison of FC test results showed that the mean verified FC count ratio (7-h FC count/24-h FC count) for surface water samples was 1.08. The mean FC count ratio (7-h FC count/24-h FC count) for unchlorinater wastewater ranged from 1.95 to 5.05. Verification of yellow FC colonies from m-7-h FC medium averaged 97%. Data from field tests on Lake Michigan bathing beach water samples showed that unverified 7-h FC counts averaged 96% of the 24-h FC counts. The 7-h FC test was found to be suitable for the examination of surface waters and unchlorinated sewage and could serve as an emergency test for detection of sewage or fecal contamination of potable water.

Culture Media↗