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 beta-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 beta-lactam/carbapenem antibiotics (imipenem, 100%). ESBL-producing E. coli (n = 4) and K. pneumoniae isolates (n = 8) were also sensitive to non-beta-lactam aminoglycosides (amikacin, 80.00% and 88.89%, respectively). ESBL producers were most resistant to beta-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 blasnv. 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.

Automated summary

The study found ESBL-producing E. coli and K. pneumoniae in raw vegetables, showing high resistance to beta-lactam antibiotics but good sensitivity to beta-lactam/carbapenem antibiotics. The genes carried by these bacteria may be associated with food chains and humans, suggesting that raw vegetables could serve as an important route for the transmission of ESBL-resistant bacteria to humans.