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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]

Examination of naturally occurring C. parvum oocysts from environmental water samples has previously been hampered by the inability to determine the public health significance of detected organisms. As a result the safety of drinking water supplies was in question. These limitations have been resolved through the development and application of a method that incorporates immunomagnetic separation (IMS) and an infectivity determination using an integrated cell culture, polymerase chain reaction assay (CC-PCR). Briefly, the method concentrates water samples by filtration or centrifugation and isolates oocysts by IMS. An acidified Hank's balanced salt solution (HBSS) containing 1% trypsin was used for the dissociation of captured oocysts from the IMS beads. In vitro HCT-8 cell culture of purified oocysts was performed in 96-well microtiter plates and infected cells were detected using PCR primers specific for C. parvum. A total of 242 raw source waters or filter backwash water samples from twenty five sites in the U.S. were analyzed to validate the procedure. Oocyst seeded in raw and filter backwash water samples were used to evaluate recovery efficiencies and performance of the CC-PCR protocol with different water quality matrices. The CC-PCR detected infectious Cryptosporidium parvum in 6 of 121 (5.0%) raw and 9 of 122 (7.4%) filter backwash water samples. All CC-PCR positive samples were confirmed by cloning and DNA sequence analysis of the PCR products. Isolates were shown to originate from human and animal sources. Grouping of genotypes permitted evaluation of strain diversification and variation. Current studies are using this technique to examine oocysts in various watersheds and in the finished drinking water of over 80 surface water treatment plants. [ABSTRACT FROM AUTHOR]

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]