UTTAR PRADESH JOURNAL OF ZOOLOGY

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli in bovine milk is an important concern for animal health, food safety and antimicrobial resistance surveillance. The present study investigated the occurrence, antimicrobial resistance pattern and distribution of selected ESBL genes among E. coli isolates recovered from bovine milk samples collected from the Awadh region of Uttar Pradesh, India. A total of 240 milk samples were collected from cattle and buffaloes, including apparently normal and clinically mastitic milk samples. Presumptive E. coli isolates were identified using cultural and biochemical methods and were further confirmed by PCR targeting the species-specific uspA gene. Among the samples examined, 74 isolates were confirmed as E. coli, giving an overall occurrence of 30.83%. Phenotypic detection of ESBL production using screening and confirmatory methods identified 33 ESBL-producing E. coli isolates, representing 44.59% of the confirmed E. coli isolates. Antimicrobial susceptibility testing of phenotypically confirmed ESBL-producing isolates showed complete resistance to ampicillin, cefotaxime, ceftazidime and cefpodoxime, while comparatively lower resistance was observed against aminoglycosides, chloramphenicol and carbapenems. Multidrug resistance was recorded in 25/33 (75.76%) phenotypically ESBL-positive isolates. Molecular analysis of ESBL-associated genes showed the predominance of bla-CTX-M-1 among genotypically positive isolates, followed by bla-TEM and bla-SHV. Co-occurrence of more than one ESBL gene was also observed in some isolates. The findings indicate the presence of ESBL-producing and multidrug-resistant E. coli in bovine milk samples from the study area. These results emphasized the need for routine antimicrobial resistance monitoring, hygienic milk production practices and prudent antimicrobial use in dairy animals.