Antimicrobial Resistance Profiling of Shiga Toxin-Producing Escherichia coli Isolated from Diarrhoeic Cattle

Cattle are recognized as important reservoirs of Shiga toxin-producing Escherichia coli (STEC), contributing to the transmission of antimicrobial-resistant strains through the food chain and environment. The present study investigated the phenotypic and genotypic antimicrobial resistance profiles of 40 molecularly confirmed STEC isolates recovered from diarrhoeic cattle in Jaipur, Rajasthan. Antimicrobial susceptibility testing was performed against 11 antimicrobial agents using the Kirby-Bauer disc diffusion method. The highest susceptibility was observed against ampicillin/sulbactam, doxycycline, imipenem and chloramphenicol (80% each), whereas the highest resistance was detected against ciprofloxacin (97.5%), nitrofurantoin (95%) and co-trimoxazole (90%). Multidrug resistance was observed in 39 (97.5%) isolates, and resistotyping revealed 24 distinct resistance patterns, with R-1 as the predominant profile (25.0%). Molecular analysis detected tetA and blaTEM resistance genes in 17.5% and 15.0% of isolates, respectively. The coexistence of virulence-associated STEC with multidrug resistance highlights the potential public health risk posed by cattle as reservoirs of antimicrobial-resistant zoonotic pathogens. These findings emphasize the importance of antimicrobial stewardship, continuous surveillance and One Health approaches to control the emergence and spread of resistant STEC in livestock populations.