BACKGROUND AND OBJECTIVESExtended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae have become a serious public health hazard worldwide. This study aimed to identify and investigate the occurrence of ESBL-producing Escherichia coli strains, isolated from bovine clinical mastitis cases and Non-pathogenic bovine fecal strains in Mashhad Province.MATERIALS AND METHODSA total of ۱۰۷ isolates were studied, ۷۵ E. coli strains were isolated from bovine clinical mastitis cases, and ۳۲ isolates were non-pathogenic fecal strains. To phenotypic confirmation of ESBL-producing strains, combination disc diffusion method was applied according to the CLSI guidelines. Additionally, Genotypic and sequencing analyses of ESBL resistance genes were conducted on all isolates by using polymerase chain reaction.RESULTS AND DISCUSSIONOverall, ۱۲ of ۱۰۷ E. coli isolates (۱۱.۲۱%) were identified as ESBL-producers. ۷ isolates (۹.۳%) belonged to the mammary pathogenic group and ۵ isolates (۱۵.۷%) belonged to the fecal strains group. Of these ESBL-producing E. coli, the prevalence of blaCTX-M, blaTEM was ۸۳.۳۳% and ۳۳.۳۳%, respectively. Also, ۳ isolates (۲۵%) carry both blaCTX-M and blaTEM genes at the same time. None of the isolates with positive ESBL phenotype carried blaSHV and blacmy genes.CONCLUSIONFecal strains can be a potential source of E. coli carrying resistance genes that may spread to the environment or food chain, and could pose serious and catastrophic health risks. Authorities should cling to the concept of One Health to minimize the risk of new varieties.

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