Georgia Journal of Science


Escherichia coli and enterococci were enumerated in water collected biweekly for one year at ten stations in the Alapahoochee River system. The concentrations of E.coli were usually below a standard of 576 colony forming units (cfu) per 100 ml, except after heavy rain. At five stations the concentrations of enterococci were gener­ally above a standard of 151 cfu/100 ml. Concentrations of both groups showed a direct but weak correlation with pH. For quality control, 772 colonies typical of E. coli and 773 colonies typical of enterococcus were tested by the appropriate verification procedures. Sixty-six (8.5%) of the former, and 57 (7.4%) of the latter, appeared to be false positives. Further study of 51 apparent false positive E. coli isolates showed that only 15.7% did not contain E.coli, indicating an actual false positive rate of about 1.3%. Further study of 18 false positive enterococcus isolates showed that 16.7% were Enterococ­cus species and 83.3% were Streptococcus species. Thus the actual false positive rate was estimated to be 6.2 %.

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