Occurrence of Virulence Genes Associated with Diarrheagenic Pathotypes in Escherichia coli Isolates from Surface Water

Abstract

ABSTRACTEscherichia coliisolates (n= 300) collected from six sites in subtropical Brisbane, Australia, prior to and after storm events were tested for the presence of 11 virulence genes (VGs) specific to diarrheagenic pathotypes. The presence ofeaeA,stx1,stx2, andehxAgenes specific for the enterohemorrhagicE. coli(EHEC) pathotype was detected in 56%, 6%, 10%, and 13% of isolates, respectively. The VGsastA(69%) andaggR(29%), carried by enteroaggregative (EAEC) pathotypes, were frequently detected inE. coliisolates. The enteropathogenicE. coli(EPEC) genebfpwas detected in 24% of isolates. In addition, enteroinvasiveE. coli(EIEC) VGipaHwas also detected in 14% of isolates. During dry periods, isolates belonging to the EAEC pathotype were most commonly detected (23%), followed by EHEC (11%) and EPEC (11%). Conversely, a more uniform prevalence of pathotypes, EPEC (14%), EAEC (12%), EIEC (10%), EHEC (7%), and ETEC (7%), was observed after the storm events. The results of this study highlight the widespread occurrence of potentially diarrheagenic pathotypes in the urban aquatic ecosystems. While the presence of VGs inE. coliisolates alone is insufficient to determine pathogenicity, the presence of diarrheagenicE. colipathotypes in high frequency after the storm events could lead to increased health risks if untreated storm water were to be used for nonpotable purposes and recreational activities.