Molecular Characterization of Virulent Genes and Antimicrobial Resistance Patterns of Escherichia coli Isolated From Calf Scours in Western Iran

OBJECTIVE: This study was designed to determine the virulence factors and antimicrobial resistance profiles of Escherichia coli pathotypes isolated from neonatal calf diarrhoea in Western Iran. METHODS: A total of 350 diarrhoeic faecal samples were collected. The samples were assessed for the presence of E. coli phenotypically. The molecularly confirmed isolates were further classified as different pathotypes on the basis of the genotypic traits. Additionally, the distribution of diverse serotypes and the antimicrobial resistance profile of the isolates were determined. RESULTS: Among the 307 E. coli isolates, 235 isolates could be categorized as the following pathotypes: enterohaemorrhagic E. coli (EHEC), 36.59%; enteropathogenic E. coli (EPEC), 20.42%; enterotoxigenic E. coli (ETEC), 14.46%; Shiga-toxigenic E. coli (STEC), 12.34% and necrotoxigenic E. coli (NTEC), 11.48%. STEC O157:H7 was detected in four isolates. O103 and O15 serotypes were the most prevalent. Totally, high rates of antibiotic resistance were observed, with the most common resistance for penicillin (99.14%) and tetracycline (94.46%), and the least common for nitrofurantoin (62.16%) and neomycin (65.10%). CONCLUSION: The results substantiated the potential reservoirs of calves for various E. coli pathotypes in the region. With an emphasis on the identification of important O-serogroups and the high rates of antimicrobial resistance among the isolates, the need for continuous monitoring, strict biosecurity measures in cattle farms and proper antibiotic stewardship are underscored to prevent the transmission of pathogenic and resistant strains to humans.