Donald J. Reasoner

Assessment of equine fecal contamination: the search for alternative bacterial source-tracking targets.

16S rDNA clone libraries were evaluated for detection of fecal source-identifying bacteria from a collapsed equine manure pile. Libraries were constructed using universal eubacterial primers and Bacteroides-Prevotella group-specific primers. Eubacterial sequences indicated that upstream and downstream water samples were predominantly beta- and gamma-Proteobacteria (35 and 19%, respectively), while the manure library consisted predominantly of Firmicutes (31%) and previously unidentified sequences (60%). Manure-specific eubacterial sequences were not detectable beyond 5 m downstream of the pile, suggesting either poor survival or high dilution rates. In contrast, Bacteroides and Prevotella sp. sequences were detected both in manure and downstream using group-specific primers. Novel sequences from Bacteroides and Prevotella analysis produced an equine-specific phylogenetic cluster as compared to previous data sets obtained for human and bovine samples. While these results suggest that some anaerobic fecal bacteria might be potential identifiers for use in source-tracking applications, a comprehensive examination of environmental sequences within these species should be performed before methods targeting these bacterial groups are applied to watersheds for development of microbial source-tracking protocols.

Survival of Escherichia coli O157:H7 in drinking water associated with a waterborne disease outbreak of hemorrhagic colitis

Survival characteristics were similar for two strains of Escherichia coli O157: H7 and a typical indicator strain of E. coli in a portable ground water source. Die‐off was more rapid at 20°C than at 5°C. There was no significant difference among the rates of survival for the strains examined.

Monitoring Heterotrophic Bacteria in Potable Water

Measurements of bacterial populations in water have been used since the beginning of sanitary bacteriology (see Chapter 21), and interest in the interpretation of the results has occupied many researchers over the intervening years. In addition to the coliform count, a more generalized bacterial counting procedure has also been used. In the United States, standardization of the methodology for general bacterial counts using a plate-counting procedure began with the activities of the Committee of Bacteriologists of the American Water Works Association from 1895 to 1898 (Prescott et al., 1950). Continued work on standardization of methods for detection of bacteria led to the inclusion of those methods in the first edition (1905) of what is now known as Standard Methods for the Examination of Water and Wastewater (Standard Methods, hereafter).

Vibrio cholerae 01 can assume a ‘rugose’ survival form that resists killing by chlorine, yet retains virulence

Vibrio cholerae 01 is able to shift between smooth and rugose colonial morphologies. Cultures of smooth V. cholerae strains were inactivated in less than 20 s at a concentration of 1.0 mg l‐1 free chlorine. In contrast, cultures of rugose variants exposed to this concentration of chlorine showed an initial rapid drop in viable counts, followed by persistence of a protected subpopulation of cells. Viable V. cholerae could still be recovered from rugose cultures even after exposure to 2.0 mg l‐1 free chlorine for 30 min. Preliminary studies suggest that resistance to killing by chlorine was due to formation of cell aggregates enclosed in a gelatinous mucoid material. Rugose strains appeared to be fully virulent, based on their ability to adhere to Caco‐2 cells and elicit fluid accumulation in rabbit ileal loops. Our data suggest that the V. cholerae rugose phenotype represents a fully virulent survival form of the organism that can persist in the presence of free chlorine.

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.

Home Treatment Devices and Water Quality

Drinking water quality is not uniform in its characteristics. While it may meet current government regulations for a safe supply, there can be pronounced differences in hardness, taste, odor, and other properties. Furthermore, there is growing evidence that groundwater quality in some small systems may have undesirable microbial, organic, inorganic, or radionuclide contaminants related to the source water characteristics of the supply. Periodic spills of a variety of pollutants into surface waters may also challenge the effectiveness of existing treatment processes in some public water supplies.

Detection of Escherichia COD 01 57:H7 in water from coliform enrichment cultures

E.W. RICE, C.H. JOHNSON AND D.J. REASONER. 1996. 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 β‐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.

Bioassay procedure for predicting coliform bacterial growth in drinking water

Abstract Water quality degradation due to the growth of microorganisms is an area of concern for many water utilities. To date, the procedures developed for determining the amount of biodegradable material present in potable water have utilized heterotrophic non‐coliform bacteria as bioassay seed organisms. A procedure was developed which utilized coliform bacteria as the bioassay organisms for determining the ability of the water to support and promote growth of coliform bacteria. The bioassay procedure can be used to evaluate the effect of various unit processes upon the biological stability of the product water.

Detection of Escherichia coli in water using a colorimetric gene probe assay

Abstract A commercially available DNA hydribization assay (Gene‐trak(R), Framingham, MA, USA) was compared with the EC‐MUG procedure for the detection of Escherichia coli in water. The gene probe gave positive responses for pure cultures of E. coli, E. coli 0157:H7, E. fergusonii. Shigella sonnei, S. dysenteriae and S. boydii. The hybridization assay was capable of detecting E. coli in environmental samples and survivors among chlorine exposed cells.

Bacteriological Changes Associated with Granular Activated Carbon in a Pilot Water Treatment Plant

Bacteriological analysis were performed on collected water samples from a conventional water treatment pilot plant in Cincinnati, Ohio in which granular activated carbon (GAC) has been used as the final process to assess the impact of GAC on the bacteriological quality and incidence of antibiotic resistant bacteria in water produced. Heterotrophic bacterial counts (HPC) at 20 °C was stabilized at 102 to 194 cfu mL-1 and did not markedly differ at different water treatment processes. On the other hand, slight reduction in HPC was observed for the effluent produced from sand filter and GAC contactors. Effluents produced from both the sand filter and GAC contactors showed 2 log reduction in coliforms count. Fecal coliform showed the same rate of reduction as a result of sand filtration, while it reached undetectable numbers in the effluent of GAC contactors. Subculturing the isolated strains in tryptic soy broth revealed that 61.3, 61.5, 12.6 and 8.5% of HPC at 28 °C, total coliforms and fecal coliform, respectively were non-culturable. In this case, R2A or R3A broth was used as subculturing media. The incidence of coliform resistant strains among isolates varied significantly according to the source of water samples. Multiple antibiotic resistance (MAR) was not always high in the same samples in which the overall resistance was high. The species composition varied considerably in different water samples. Selection for bacteria exhibiting resistance to antibiotic or antibiotics was observed under some experimental conditions using different doses of chlorine. The antibiotic resistance character was mostly transferable. As a conclusion, the use of GAC has no observable adverse effect on the bacteriological quality of the water produced from the pilot plant under investigation.