Evaluation of C. perfringens cpe-positive Strain as a Source Tracking Indicator of Human Contamination in Freshwater Environments

In this study, a field survey of fecal contamination indicators and Clostridium perfringens cpe(+) in river environments was conducted to verify the effectiveness of C. perfringens cpe(+) as a microbial source tracking indicator in public water bodies. In the Saijo River, which serves as a model of point source contamination from human sewage effluents, the concentrations of Escherichia coli, enterococci and C. perfringens increased after the inflow of sewage effluents, with the cpe-positive prevalence rate of C. perfringens isolates increasing from 13.3 to 21.5%. In the Nagaike River, contaminated with household sewage effluents from non-point sources, high concentrations of E. coli, enterococci, and C. perfringens cpe(+) were detected, with high cpe-positive prevalence rates of 27.6 and 26.4%. Contrarily, in the Koayu River, which is contaminated with treated wastewater from a large swine farm, an increase in the concentration of fecal contamination indicators and C. perfringens was observed; however, the cpe-positive prevalence rate of C. perfringens isolates remained unchanged, ranging as low as 3.6 and 3.9%. Altogether, our results revealed that the concentration and pollution load of C. perfringens cpe(+) is an effective microbial source tracking indicator of human fecal contamination in freshwater environments.