Multilocus sequence typing, phylogenetic grouping, serotyping, extended-spectrum beta-lactamases and antimicrobial resistance of Escherichia coli in vegetables

The increasing occurrence of extended-spectrum beta-lactamase (ESBL)-producing Escherichiacoli, particularly those resistant to antimicrobials, in foods, including vegetables, has been considered an alarming health risk. A total of 61 E. coli isolates from different vegetables were subjected to antimicrobial susceptibility testing, ESBL production, molecular detection of antimicrobial resistance and ESBL genes, virulence genes, serotyping, phylotyping and multilocus sequence typing (MLST). Among the vegetable isolates, resistance was observed most often to cefotaxime (34.4%), followed by ampicillin (31.1%) and tetracycline (21.3%). Additional screening for antimicrobial resistant genes in the E. coli isolates demonstrated the existence of sulI (100%), floSt (85.3%), qnrS (36.1%), tetA (29.5%), qnrB (3.3%), and class I integrons associated with multidrug resistance (90.2%). However, the genes qnrA, aadB, mcr-1, blaOXA-48and blaNDMwere not detected. ESBL production was found in 75% (46/61) and 37.7% (23/61) of the E. coli isolates by the double-disk synergy test and broth microdilution method, respectively.The PCR results revealed that blaTEMwas the most common ESBL type detected in the E. coli isolates, with 36 (59%) isolates carrying that, followed by bla CTX-M , which was identified in 18 (29.5%) isolates. No isolates had the blaSHV gene. The stx1, stx2 and eae virulence genes were not detected in the isolates. Molecular serotyping showed that two isolates belonged to serotype O157. Phylogenetic groups among E. coli isolated from vegetables included E (83.6%), D (11.5%), and A (4.9%). MLST genotyping of the 23 ESBL-positive E. coli showed 14 different sequence types [STs. ST388 (21.7%) was the most frequent ST, followed by ST224(13%)]. ST10 (ST10 clonal complex), ST118, and ST1642 each accounted for 8.7% of the overall. The rest of the isolates were individually classified into nine distinct STs.This study determined the antimicrobial resistance, ESBL production, different phylogenetic groups, diverse pathogenic STs, and the presence of a high-risk E. coli clone (ST10) in the isolates obtained from vegetables, which may pose serious concern for food safety and human health.