Epidemiology and Molecular Characterisation of Multidrug-Resistant Escherichia coli Isolated from Cow Milk

Abstract

Antimicrobial resistance (AMR) is a growing global issue that poses serious public health risks. This study investigated the prevalence and pattern of antimicrobial resistance of Escherichia coli in raw cow milk from 18 farms in Chattogram, Bangladesh. Out of 450 samples, 134 (29.77%) tested positive for E. coli. Antimicrobial susceptibility testing revealed high resistance rates (69.40%) to ampicillin, amoxicillin–clavulanic acid, cephalothin, and cephalexin, while resistance to norfloxacin was lowest (21.64%). All isolates were multidrug-resistant (MDR), showing resistance to three or more antimicrobial classes, with a multiple resistance index >0.2. PCR testing detected the blaTEM gene in 74.19% of isolates, the highest among extended-spectrum beta-lactamase (ESBL) genes. The blaCMY-1 gene was less prevalent (6.45%), and the tetD gene was rare (2.9%). Positive correlations were noted between antimicrobial resistance and resistance gene presence, with a strong link (r = 1) between ciprofloxacin and ceftazidime resistance. This study highlights the significant presence of MDR E. coli in raw milk, posing a potential public health threat through the food chain. It calls for urgent measures to manage AMR, including prudent antimicrobial use, enhanced surveillance, and targeted interventions in Bangladesh’s dairy sector.