Abstract

Objective: Escherichia coli drives bovine mastitis-linked economic losses; antibiotic resistance in subclinical cases underscores the need to explore its tie to disease-causing mechanisms. This research sought to analyze differences in E. coli’s antimicrobial resistance profiles in dairy cattle with subclinical mastitis by comparing data derived from genotypic, phenotypic, molecular, and computational (in silico) approaches.
Materials and Methods: This study involved a random selection of 381 dairy cows from the Baghabari milk belt, Bangladesh’s largest and most significant milk-producing region. In vitro and deep molecular analysis, including polymerase chain reaction (PCR) and whole-genome sequencing, was performed for the subclinical mastitis-induced sample.
Results: This study revealed that 28.34% of dairy cows were suffering from subclinical mastitis with complete resistance against ampicillin and ceftazidime in antibiotic susceptibility tests. In PCR analysis, the tetracycline resistance gene was found along with β-lactam and fluoroquinolone drug resistance genes. While a total of 50 antibiotic-resistant genes were identified in whole-genome sequencing. Efflux pump (76%) was the major antibiotic resistance pathway, which is an alarming issue for host–pathogen relationships as well as leading to the multidrug resistance to pan-drug resistance phenomenon and the emergence of extensively drug-resistant pathogens.
Conclusion: The diversity in drug resistance patterns triggers complications not just in managing mastitis but also in safeguarding healthy milk production.

Key words: Antibiotic resistance; E. coli; dairy milk; subclinical mastitis