Prevalence and Antimicrobial Resistance Patterns of <i>Escherichia coli</i> Isolated From Broiler Chickens in Sylhet District of Bangladesh

The emergence of antimicrobial resistance (AMR) Escherichia coli in poultry farming is a growing global public health concern, particularly in Bangladesh, where the use of antibiotics remains largely unregulated. This study aimed to determine the prevalence and AMR patterns of E. coli isolated from broiler chickens in Sylhet district of Bangladesh and to investigate the network of coexisting resistance traits among the isolates. A total of 130 samples (44 cloacal, 46 faecal, 21 liver and 19 intestinal) were collected from live and dead broiler chickens in the Sylhet district of Bangladesh from July 2020 to June 2021. E. coli was detected in 77.7% of samples by standard cultural and biochemical tests, with 65.4% confirmed by polymerase chain reaction (PCR) targeting the malB gene. Antibiotic susceptibility testing revealed complete (100%) resistance to tetracycline (TE), cloxacillin (CLOX) and co-trimoxazole (COT), with 91.8% resistance to erythromycin (E). Gentamicin (GEN) exhibited intermediate resistance (69.4%), whereas azithromycin (AZM) was the most sensitive, with 58.8% of the isolates demonstrating susceptibility. Faecal samples had the highest E. coli prevalence (84.8%), and liver samples had the lowest (66.7%). All isolates demonstrated multidrug resistance (MDR) in different combinations, with over one-third exhibiting resistance to six or more antibiotics. The coexistence network revealed that resistance to TE, CLOX and COT frequently occurred together, whereas GEN exhibited a distinct resistance pattern characterized by limited co-resistance with other antibiotics. The findings of this study extend beyond local concerns, carrying global implications for food safety, and emphasize the urgent need for stricter antibiotic regulations to mitigate the zoonotic transmission of MDR E. coli to humans. SUMMARY: The study reported a 77.7% prevalence of Escherichia coli in broiler chickens in Sylhet, Bangladesh with alarming resistance patterns, including complete (100%) resistance to several antibiotics (tetracycline, cloxacillin and co-trimoxazole), underscoring an urgent public health concern. The results revealed critical resistance trends, showing that several antibiotics are losing their effectiveness, which could threaten sustainable poultry farming and food safety. The correlation and coexistence network analysis identified frequent resistance linkages among specific antibiotics, suggesting shared pathways that could drive co-selection in resistant E. coli populations. The study emphasizes the pressing need for stricter antibiotic regulations, enhanced AMR surveillance and improved biosecurity measures to mitigate the spread of multidrug-resistant E. coli, with implications for both human and animal health.