Occurrence of Diarrheagenic Virulence Genes and Genetic Diversity in Escherichia coli Isolates from Fecal Material of Various Avian Hosts in British Columbia, Canada

Contamination of surface water by fecal microorganisms originating from human and nonhuman sources is a public health concern. In the present study,Escherichia coli isolates (n = 412) from the feces of various avian host sources were screened for various virulence genes:stx 1 andstx 2 (Shiga toxin-producingE. coli [STEC]),eae (enteropathogenicE. coli [EPEC]),est -h,est -p, andelt (encoding heat-stable toxin [ST] variants STh and STp and heat-labile toxin [LT], respectively) (enterotoxigenicE. coli [ETEC]), andipaH (enteroinvasiveE. coli [EIEC]). None of the isolates were found to be positive forstx 1 , while 23% (n = 93) were positive for onlystx 2 , representing STEC, and 15% (n = 63) were positive for onlyeae , representing EPEC. In addition, five strains obtained from pheasant were positive for bothstx 2 andeae and were confirmed as non-O157 by using anE. coli O157rfb (rfb O157 ) TaqMan assay. Isolates positive for the virulence genes associated with ETEC and EIEC were not detected in any of the hosts. The repetitive element palindromic PCR (rep-PCR) fingerprint analysis identified 143 unique fingerprints, with an overall Shannon diversity index of 2.36. Multivariate analysis of variance (MANOVA) showed that the majority of the STEC and EPEC isolates were genotypically distinct from nonpathogenicE. coli and clustered independently. MANOVA analysis also revealed spatial variation among theE. coli isolates, since the majority of the isolates clustered according to the sampling locations. Although the presence of virulence genes alone cannot be used to determine the pathogenicity of strains, results from this study show that potentially pathogenic STEC and EPEC strains can be found in some of the avian hosts studied and may contaminate surface water and potentially impact human health.