Sharing of Ribotype Patterns of Escherichia Coli Isolates During Baseflow and Stormflow Conditions

Factors affecting bacterial source tracking are important to understand because they affect the amount of sampling needed to describe fecal sources in a watershed adequately. The study area was a 76-kilometer reach of the Chattahoochee River and its tributaries in Metropolitan Atlanta, Georgia. Escherichia coli was isolated from water samples collected during baseflow and stormflow conditions from four mainstem and eight tributary sites; 262 isolates were ribotyped and assessed for their similarity. The vast majority of the E. coli ribotype patterns were unshared, whether the comparisons were between baseflow and stormflow conditions at one location, or between one location and another. The data suggest that either baseflow and stormflow conditions affected sharing of ribotype patterns, or that the sample size was too small to characterize the sharing adequately. Regardless, the results suggest that a large sampling of E. coli isolates is needed during various flow conditions from watersheds with complex land-use patterns for adequate bacterial source tracking.