2020 Volume 76 Issue 7 Pages III_431-III_440
This study is aiming at clarifying the behavior of antimicrobial resistant E. coli discharged on a watershed where livestock farming is active. To this end field investigations in non-rainy events and rainy events were carried out at several locations on Yasu River and Hino River in Shiga Prefecture. The results indicated that increase in the concentarations of E. coli and anitimicrobial E. coli was observed in increasing river flow due to rainy events. To investigate the effect of rainfall to the increase of E. coli concentrations in a river, a continuous sampling campaign at a location on Yasu River was performed in a rainy event. As the results, 1) during a rainy event, E. coli and antimicrobial resistant E. coli concetrations were elevated, 2) the behaviors in rainy runoff of the river were different among E. coli, ampicillin resistant E. coli, and tetracycline resistant E. coli, which suggests the diffenece in their origins and runoff mechanisms, and 3) the relastionship between pollutant loads (L) of E. coli, anitimicrobial resistant E. coli and river flow (Q) was clarified based on actual field measurements for the first time.