Escherichia coli O157 in natural river water

Abstract

Verocytotoxin-producing Escherichia coli (VTEC) O157 can cause haemolytic diarrhea and haemolytic uraemic syndrome, and most outbreaks caused by this strain have been food or water related. Cattle are known to be major reservoirs for VTEC including E. coli O157, and this strain has also been isolated from drinking water, treated water and sewage. E. coli O157 was frequently detected in natural river water by immunological and molecular biological methods, even if it was not detected by traditional culture methods. To clarify the physiological state of E. coli O157, flow cytometry was applied with the DVC or the vital staining method. Physiolocially active E. coli O157 was found to be distributed in natural river water. Bacteriophages carrying the sltII gene were also detected in sewage, and they could transform E. coli O157. These results indicate that monitoring not only bacterial cells but also slt genes is necessary to clarify the dynamics of E. coli O157 in natural environments, and examination of the viable but non-culturable state of E. coli O157 is also essential to prevent disease outbreaks.