The Burden of Escherichia coli Pathotypes among Diarrheic Farm Animals: A Possible Zoonotic Relevance

Abstract

Pathogenic strains of Escherichia coli possess virulence factors that contribute to both intestinal and extraintestinal infections in both humans and animals. Farm animals can serve as a potential source for these types of E. coli strains. This study aimed to determine the virulence genes and related pathotypes of E. coli isolated from diarrheic farm animals and their public health importance. Rectal swabs were collected from 175 diarrheic farm animals (49 cattle, 69 sheep, and 57 goats). Samples were prepared for isolation of E. coli through enrichment in tryptic soya broth and then plating on Eosin methylene blue agar, whereas the identification of E. coli was performed based on colony morphology, biochemical tests, and molecular confirmation by PCR. Furthermore, the determination of the virulence factors associated with E. coli pathotypes was done by molecular technique to amplify the virulence genes including adhesins (sfa, papC, sepA, etrA, aer, feaG, fsaA, and eaeA), capsule synthesis (rfc), and toxins (cnf1, hlyA, eltA, estA, exhA, stx1, and stx2). Moreover, phylogenetic analysis was done via sequencing of the 16s rRNA genes from the strains that carry virulence genes, as well as the statistical analysis was done through the production of the hierarchically clustered heat map. Pathogenic E. coli was found in 39.4% of the examined animals. Fifteen out of sixteen virulence genes were detected among E. coli isolates from different farm animals, including cattle, sheep, and goats. ExPEC pathotype was predominated among cattle and sheep isolates whereas, ETEC pathotype is more frequent among goat isolates. The sequence analysis of 16s rRNA sequences revealed similarity between farm animal isolates and those from humans that were retrieved from GenBank. In conclusion, this study highlights the potential role of diarrheic farm animals in the epidemiology of pathogenic E. coli pathotypes which may have public health implications.