Biofilm and antimicrobial resistance profile of extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase producing Enterobacteriaceae in vegetables and salads

This study characterized 360 vegetables and salad samples for extended-spectrum beta-lactamase (ESBL)- and AmpC-beta-lactamase-producing Enterobacteriaceae. The isolated bacteria species were processed for beta-lactamase production, antimicrobial resistance (AMR) and other virulence potentials following standard microbiological and spectrometry methods. The ESBL and AmpC-beta-lactamase-producing bacteria were positive in 16/360 (4.4%) and 4/360 (1.1%) of the vegetable samples, respectively. Molecular identification of the bacterial isolates revealed them as follows: 37  E. coli, 6 Klebsiella pneumoniae and 4 Klebsiella variicola. The total number of ESBL-producing enterobacterial phenotypes was 38, while the AmpC-beta-lactamase-producing enterobacterial phenotype was 9. The beta-lactamase-producing enterobacterial morphotypes revealed that 16/47(34.0%) were rough and moist morphotypes, 25/47(53.2%) were rough and dry morphotypes, while 6/47(12.8%) were smooth and white morphotype. The biofilm profile included strong biofilm 41(87.2%), moderate biofilm 4(8.5%) and weak biofilm 2(4.3%), as all the isolates formed biofilm on LB broth. Fourteen multi-drug resistance (MDR) phenotypes were observed in the beta-lactamase-producing E. coli isolates. A total of 40/47(85.1%) isolates had ≥1 β-lactamase gene and other AMR genes, with the bla CTX-1 being the most prevalent. Our findings conclude that food vegetables are important reservoirs of beta-lactamase-producing enterobacteria and a potential health risk to consumers of unprocessed vegetables.