Ribotyping to Determine the Source of Fecal Coliform Contamination in Three Household Wells Near Cochran, Georgia

Abstract

The Bleckley County Health Department reported that three households near Cochran, Georgia tested positive for fecal coliforms in their wells. Fecal coliforms are bacteria that are a measure of fecal contamination and are typically found in the intestines of warm-blooded animals, including humans. We were asked to isolate one bacterial species of these fecal coliforrns, Escherichia coli, and to determine the source of the isolates by ribotyping. Ribotyping is a method to identify a subspecies of a bacterium by comparing differences in their DNA. We quantified the number of E. coli in water samples from one pond, two streams, a sinkhole, and three household wells and their accompanying septic systems. The pond, streams, and sinkhole are all connected. We ribotyped 51 E. coli isolates. Twelve different ribotypes were observed among the water sources and the household wells with their accompanying septic systems. Two ribotype patterns were observed from the septic systems, ten patterns among the pond, sinkhole, and two streams, and six patterns among the three household wells. At 100% similarity, all the ribotype patterns of E. coli from the household wells were associated with patterns from the pond, sinkhole, or two streams. The similarity of E. coli ribotype patterns from the household wells with the septic systems were only 80 and 86%. The results suggest that the point source of the E. coli contamination was the pond, sinkhole, or two streams, and not the septic systems.