OCCURRENCE AND SOURCE OF ANTIMICROBIAL RESISTANT ESCHERICHIA COLI IN THE LAKE BIWA AND ITS WATERSHED RIVERS

Abstract

 This study aimed to investigate the occurrence and the source of the antimicrobial-resistant E. coli in the Lake Biwa watershed. To achieve this, field survey for antimicrobial-resistant E. coli were carried out at several locations on Lake Biwa in Shiga Prefecture, Japan and its watershed rivers with and without rainfall events. Results indicated that the concentrations of E. coli and antimicrobial-resistant E. coli could increase when the river streamflow increased due to the rainfall. To further investigate the effect of precipitation on the increasing of E. coli concentrations in a river, continuous 5-day samplings were performed at a location on Yasu River during rainfall events. Further, the potential contamination source of tetracycline-resistant E. coli isolated from wastewater treatment plants, rivers, and Lake Biwa was investigated by the whole-genome sequence analysis of E. coli isolates. Correlation between the concentration of antimicrobial-resistant E. coli in waters and the land use in the watershed was also analyzed. Results in this study suggest that both human and livestock influence the presence of antimicrobial-resistant bacteria in the Lake Biwa watershed.