Prevalence of Diarrhea-Associated Virulence Genes and Genetic Diversity in Escherichia coli Isolates from Fecal Material of Various Animal Hosts

Abstract

ABSTRACTIn order to assess the health risk associated with a given source of fecal contamination using bacterial source tracking (BST), it is important to know the occurrence of potential pathogens as a function of host.Escherichia coliisolates (n= 593) from the feces of diverse animals were screened for various virulence genes:stx1andstx2(Shiga toxin-producingE. coli[STEC]),eaeand EAF (enteropathogenicE. coli[EPEC]), STh, STp, and LT (enterotoxigenicE. coli[ETEC]), andipaH(enteroinvasiveE. coli[EIEC]). Eleven hosts were positive for only theeae(10.11%) gene, representing atypical EPEC, while two hosts were positive for botheaeand EAF (1.3%), representing typical EPEC.stx1,stx2, or bothstx1andstx2were present in 1 (0.1%,) 10 (5.56%), and 2 (1.51%) hosts, respectively, and confirmed as non-O157 by using aE. coliO157rfb(rfbO157) TaqMan assay. STh and STp were carried by 2 hosts (2.33%) and 1 host (0.33%), respectively, while none of the hosts were positive for LT andipaH. The repetitive element palindromic PCR (rep-PCR) fingerprint analysis identified 221 unique fingerprints with a Shannon diversity index of 2.67. Multivariate analysis of variance revealed that majority of the isolates clustered according to the year of sampling. The higher prevalence of atypical EPEC and non-O157 STEC observed in different animal hosts indicates that they can be a reservoir of these pathogens with the potential to contaminate surface water and impact human health. Therefore, we suggest thatE. colifrom these sources must be included while constructing known source fingerprint libraries for tracking purposes. However, the observed genetic diversity and temporal variation need to be considered since these factors can influence the accuracy of BST results.