Abstract

Background. The increasing prevalence of broad-spectrum ampicillin-resistant and third-generation cephalosporin-resistant Enterobacteriaceae, particularly Escherichia coli and Klebsiella pneumoniae, has become a global concern, with its clinical impacts on both human and veterinary medicine. This study examined the prevalence, antimicrobial susceptibility, and molecular genetic features of extended-spectrum _- lactamase (ESBL)-producing E. coli and K. pneumoniae isolates from 10 types of raw vegetables. Methods. In total, 305 samples were collected from 9 markets in Nakhon Si Thammarat, Thailand, in 2020. Results. ESBL-producing E. coli and K. pneumoniae isolates were found in 14 of the 305 samples obtained from 7 out of 10 types of vegetables (4.6% of the total). Further, 14 ESBL-producing E. coli (n D 5=14) and K. pneumoniae isolates (n D 9=14) (1.6% and 3.0%, respectively) were highly sensitive to _-lactam/carbapenem antibiotics (imipenem, 100%). ESBL-producing E. coli (nD4) and K. pneumoniae isolates (nD8) were also sensitive to non-_-lactam aminoglycosides (amikacin, 80.00% and 88.89%, respectively). ESBL producers were most resistant to _-lactam antibiotics, including ampicillin (85.71%) and the cephalosporins cefotaxime and ceftazidime (64.29%). The most frequently detected gene in ESBL-producing E. coli and K. pneumoniae was blaSHV. However, two ESBL-producing E. coli isolates also carried three other ESBL-encoding variants, blaTEM, blaCTX-M1, blaGES and blaTEM, blaSHV, blaCTX-M9, which may be due to their association with food chains and humans. Discussion. Indeed, our results suggest that raw vegetables are an important source of ESBL-resistant E. coli and K. pneumoniae, which are potentially transmittable to humans via raw vegetable intake.