Antibiotic-resistant bacteria and antibiotic residue contamination in fresh raw foods sold at wholesale markets in Thailand

Abstract

Objective: To investigate the extent of antibiotic-resistant bacteria and antibiotic residue contamination in fresh raw foods sold at wholesale markets in Thailand, which may be the important drivers of antibiotic-resistant bacteria colonization and antibiotic-resistant bacterial infection in Thai population. Materials and Methods: Fresh raw foods, including food from animal products, seafoods, vegetables, fruits, and honey were purchased from two large wholesale markets in Thailand. Food samples were cultured for antibiotic-resistant bacteria and tested for the presence and amount of antibiotic residue. Results: Among 521 samples for bacterial culture, 86.9% grew at least one kind of bacteria. Enterobacteriaceae were commonly isolated and were commonly resistant to ampicillin (76.7% to 100%). ESBL-producers and ceftriaxone-resistant Enterobacteriaceae were prevalent in swine and duck samples (56.7% to 91.7%). Some isolates were resistant to co-amoxiclav (13.3% to 60.0%) and cefoxitin (5.0% to 30.0%). Colistin-resistant Enterobacteriaceae were observed in pork meat (1.4%) and chicken offal (7.0%). Ertapenem-resistant Enterobacteriaceae were detected in cha-om (26.7%). Among 501 samples for antibiotic residue testing, 37.1% contained at least one antibiotic residue. Enrofloxacin was the most prevalent antibiotic residue, followed by doxycycline and tilmicosin. Although most samples contained less antibiotics than the maximum residue limit (MRL), 7.0% contained an amount of at least one antibiotic above the MRL. Conclusion: Many fresh raw foods sold at wholesale markets in Thailand were contaminated with antibiotic-resistant bacteria, and some contained antibiotic residues. Therefore, Thai people are at risk of being colonized with antibiotic-resistant bacteria and developing antibiotic-resistant bacterial infection due to consuming foods contaminated with antibiotic-resistant bacteria or containing antibiotic residues.