AWWA WQTC65979

The objective of this study was to evaluate the usefulness of microbial source tracking (MST) strategies for characterizing and determining relatedness among isolates obtained from a drinking water treatment plant and distribution systems. Approximately eighty bacterial isolates were obtained from three water utilities in North America. The three utilities had identified coliforms in their distribution systems and preliminary analyses by the utilities identified the causes of the occurrences as being either the water treatment plant (or the source), regrowth in the distribution system or invasive distribution system operations (e.g., main break repair). Isolates from Pinellas County, Florida were sampled from the water treatment facility at different stages of the treatment process, whereas isolates from Laval, Quebec and Lexington, Kentucky were sampled at different points in the distribution system. All bacterial isolates underwent subsequent characterization using enzyme-based and molecular methods. Substrate utilization tests (API and Biolog) were used to determine the identity of the isolates. Both API and Biolog are phenotypic identification systems that utilize a series of colorimetric reactions to generate a metabolic profile for unknown bacterial isolates. Isolates were further characterized by PFGE analysis to determine the degree of genetic variation between isolates. PFGE was used to separate genomic DNA digested with a rare-cut restriction enzyme (XbaI). The band pattern obtained from PFGE analysis was used to create a profile for each isolate. The profiles of isolates were compared to determine the genetic relatedness between isolates and whether microbial occurrences at two different sampling points were related. Includes 8 references.