Isolation and molecular characterization of ESBL-producing Escherichia coli from animal-derived food samples in Bidar, Karnataka

Abstract

The global rise in antimicrobial resistance (AMR), particularly due to Extended Spectrum Beta-Lactamase (ESBL)-producing Escherichia coli (ESBL-Ec), poses a serious public health threat. Foods of animal origin are increasingly recognized as important reservoirs and transmission vehicles for these resistant bacteria. This study aimed to isolate, phenotypically detect, and molecularly characterize ESBL-producing E. coli from meat and milk samples collected from various sources in the Bidar district of Karnataka, India. A total of 180 samples—including chicken, chevon, beef, kara beef, pork, and raw milk—were collected from five taluks of Bidar. Standard microbiological techniques were employed for the isolation and identification of E. coli. ESBL production was confirmed phenotypically using the combination disc method as per CLSI guidelines. Molecular detection of blaCTX-M, blaTEM, and blaSHV genes was carried out using PCR. Out of 180 samples, 109 E. coli isolates were recovered, of which 74 (67.88%) were phenotypically confirmed as ESBL producers. Among these, 52 isolates (70.27%) carried one or more ESBL genes, with blaCTX-M being the most prevalent (73.08%), followed by blaTEM (53.85%) and blaSHV (26.92%). Co-occurrence of multiple genes was observed in 21 isolates, with one isolate harboring all three genes. The study confirms the significant presence of ESBL-producing E. coli in foods of animal origin in Bidar, indicating the potential risk of AMR transmission through the food chain. The findings underscore the urgent need for AMR surveillance, prudent antibiotic use in veterinary practices, and strengthening of food hygiene and safety measures in the region.