Retail cattle meat as a reservoir of multidrug-resistant Salmonella harboring β-lactamase genes in Sylhet, Bangladesh

An increasing number of multidrug-resistant Salmonella enterica serovars, capable of producing ESBL enzymes, are emerging globally as important food-borne pathogens and pose a serious threat to public health. The study aimed to assess the prevalence of these strains, their resistance pattern, and the percentage of beta-lactam genes that were present at the molecular level for the Salmonella Typhimurium and Salmonella Enteritidis strains isolated from the retail meat of cattle sold in the Sylhet region of Bangladesh. Three hundred meat swab samples were collected from 13 upazilas within the Sylhet district. The isolation and identification of the Salmonella species were carried out using culture, biochemistry, and molecular (PCR) methods. Antimicrobial susceptibility was performed using the Kirby-Bauer disc diffusion test. Among the molecular characterization studies, the nine beta-lactam genes studied include: bla_TEM, bla_SHV, bla_CTX-M-grp1, bla_CTX-M-grp2, bla_CTX-M-grp9, Multicase_ACC, Multicase_MOX, Multicase_DHA, and bla_OXA. Out of 300 samples, 82 (27.3%) were positive for S. enterica, including 41 (13.7%) S. Typhimurium and 31 (10.3%) S. Enteritidis. Molecular screening revealed high prevalence of bla_TEM (73.2% in S. Typhimurium, 77.4% in S. Enteritidis) and bla_OXA (31.7% and 19.4%, respectively), while no isolates carried bla_CTX-M groups, ACC, MOX, or DHA. Both serovars displayed extensive resistance to ampicillin, ceftazidime, tetracycline, nalidixic acid, and chloramphenicol, with high susceptibility to carbapenems and aminoglycosides. Importantly, all isolates exhibited multidrug resistance with MAR indices ranging from 0.22 to 0.72, indicating exposure to high-risk contamination sources. This research reveals the alarming prevalence of multi-drug resistant Salmonella harboring β-lactamase genes in retail beef in the Sylhet region, which has the potential to be a threat to food safety and public health. This emphasizes the urgent need for robust antimicrobial stewardship and improved hygienic practices within the meat production and distribution chain.