Prevalence and characterization of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae isolated from raw vegetables retailed in Southern Thailand

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 β-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 = 5/14) and K. pneumoniae isolates ( n = 9/14) (1.6% and 3.0%, respectively) were highly sensitive to β-lactam/carbapenem antibiotics (imipenem, 100%). ESBL-producing E. coli ( n = 4) and K. pneumoniae isolates ( n = 8) were also sensitive to non-β-lactam aminoglycosides (amikacin, 80.00% and 88.89%, respectively). ESBL producers were most resistant to β-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 bla SHV . However, two ESBL-producing E. coli isolates also carried three other ESBL-encoding variants, bla TEM , bla CTX-M1 , bla GES and bla TEM , bla SHV , bla CTX-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.