Use of antibiotic resistance analysis to identify nonpoint sources of fecal pollution

A study was conducted to determine the reliability and repeatability of ant ibiotic resistance analysis as a method of identifying the sources of fecal pollution in surface water and groundwater. Four large sets of isolates of fecal streptococci (from 2,635 to 5,990 isolates per set) were obtained fr om 236 samples of human sewage and septage, cattle and poultry feces, and p ristine waters. The patterns of resistance of the isolates to each of four concentrations of up to nine antibiotics were analyzed by discriminant anal ysis. When isolates were classified individually, the average rate of corre ct classification (ARCC) into four possible types (human, cattle, poultry, and wild) ranged from 64 to 78%. When the resistance patterns of all isolat es from each sample were averaged and the resulting sample level resistance patterns were classified, the ARCCs were much higher (96 to 100%). These d ata confirm that there are measurable and consistent differences in the ant ibiotic resistance patterns of fecal streptococci isolated from various sou rces of fecal pollution and that antibiotic resistance analysis can be used to classify and identify these sources.