Microbial Source Tracking of Escherichia coli in Cassadaga Lake.

Abstract

Beaches on Cassadaga Lake in western New York State have needed to be closed numerous times by the local health department due to high fecal coliform levels measured in water samples taken from the lake. There were beach closures in the summers of 2004 and 2006, but no closures in 2005. These closures may be due to fecal pollution from wildlife or domestic animals living near the lake or to an aging sewage treatment system used by a nearby Job Corps facility. To investigate the origins of the bacteria, a microbial source tracking project was initiated on Escherichia coli isolated from the lake. During the summers of 2005 and 2006, water samples were collected five times each season from eight different lake sites. E. coli in the water samples were isolated on selective and differential media. E. coli were also isolated from goose, dog, deer, cat, duck, cow, and human fecal samples. Genomic DNA was purified from isolated E. coli strains for analysis. Repetitive element PCR (REP-PCR) using the BOX AIR Primer and amplified fragment length polymorphism (AFLP) were performed on all isolated DNA samples. For AFLP analysis, DNA samples were digested with the restriction enzymes EcoRI and Msel. Fragments were ligated to nucleotide adapters, and the ligation products were used as templates for PCR. Preselective amplification was performed using primers for the RcoRI and Msel adapters. Selective amplification was performed using an Mse+C primer and infrared dye labeled Eco+A and Eco+C primers. The PCR products were run on a poly acrylamide gel in aLI-COR DNA analyzer which facilitated the creation of images based on detection of theIR fluorescence of the dye. Data was analyzed using GelCompar II software. A library of E. coli isolates from known sources was created in the software and unknown isolates were compared against this library using Pearson product moment correlation for identification. A total of 525 E. coli samples were isolated and analyzed in the study, of these 271 were isolated from the lake and classified as unknown and 254 were isolated from known sources. The data from both summers indicate that the geese are most likely responsible for the majority of the fecal pollution in Cassadaga Lake.