Coliforms, Salmonella, and Shigella in the James River Basin
The enteric bacterial contamination in the James River Basin was assessed using routine monitoring methods and pathogen detection techniques. Samples were collected from 10 different locations, once per month for 6 months, and analyzed for fecal coliforms, E. coli and total phosphorous. The location, date, flow rate, air temperature, precipitation, water temperature, and dissolved oxygen were recorded for each sample. A portion of each sample was concentrated onto filter paper and enriched overnight in GNTSB. Molecular methods were used for the detection of Salmonella and Shigella. Biochemical tests were used to identify the non-lactose-fermenting enteric bacteria and evaluate which lactose non-fermenting bacteria were most often isolated during each month. The median fecal coliform levels for 3 locations were above the 200 CFU/100 mL EPA established limit for recreational waters. The median E. coli levels for 4 locations were above the 126 CFU/100 mL EPA established limit for recreational waters. Correlation analysis indicated bacterial levels are influenced by the flow rate and stormwater runoff, but they are independent of the phosphorous and dissolved oxygen levels. Salmonella was detected at 4 locations during September. Controlled experiments with GNTSB broth indicated it was a good general enrichment broth for mixed cultures, but it was not selective enough for the detection of stressed organisms or microbes present in low numbers.
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