Title : Antimicrobial resistance in ESBL-producing Enterobacteriaceae isolated from retail raw milk and meat
Abstract:
Background: The emergence of antimicrobial resistance (AMR) in foodborne pathogens, particularly Extended Spectrum β-Lactamase-producing Enterobacteriaceae (ESBL-E), poses serious threats to food safety and public health. This study aimed to determine the prevalence, β-lactamase gene distribution, and antimicrobial resistance patterns of ESBL-E from retail raw meat and milk in Sylhet, Bangladesh.
Methods: A total of 1,560 samples (780 meat and 780 milk) were collected from retail vendors. Pathogens were identified using cultural, biochemical, and PCR methods. Confirmed Enterobacteriaceae were screened for ESBL production by DDST, β-lactamase genes by PCR, and antimicrobial susceptibility against 16 antibiotics from 10 classes using the Kirby–Bauer method.
Results: Among 681 phenotypic ESBL-E isolates (meat: 461; milk: 220), E. coli (n=254) and K. pneumoniae (n=205) were predominant in raw milk and meat samples. In meat isolates, ESBL-E. coli carried blaTEM-1,2 was detected in 158 (83.2%), blaSHV-1 in 92 (48.4%), blaCTX-M-grp9 in 54 (28.4%), and AmpC β-lactamase genes MultiCaseDHA-1,2 in 62 (32.6%) isolates. In milk isolates, E. coli carried blaTEM-1,2 (67.2%) and MultiCaseDHA-1,2 (40.6%). Alarmingly, resistance to ampicillin (96–100%), cephalosporins (85–95%), and aztreonam (64–79%) was widespread in all isolates. Carbapenem resistance was observed in some K. pneumoniae (21.1%). MDR was present in 245 (53.1%) of ESBL-E in meat and 125 (56.8%) of milk isolates, XDR in 26.0% and 28.6%, and PDR in 7.1% and 0.9%, respectively. Ciprofloxacin resistance ranged from 25.0% to 63.6%, and tetracycline resistance exceeded 60% in S. Typhimurium and S. Enteritidis. The Multiple Antibiotic Resistance Index (MARI) ranged from 0.44 to 1.0, indicating high antimicrobial exposure.
Conclusion: This study highlights retail raw meat and milk as significant reservoirs of MDR and ESBL-producing pathogens. The detection of XDR and PDR strains, particularly from meat, underscores an urgent need for AMR surveillance, stricter antimicrobial stewardship, and improved hygiene in the food production chain to mitigate zoonotic risks.
