Abstract:
Fresh vegetables play a significant role in the human diet. However, ready-to-eat (RTE)
vegetables have been associated with increasing foodborne outbreaks including L. monocytogenes,
which is a common human pathogen associated with foodborne infections resulting in listeriosis. This
study aims to assess the resistance of vegetable-borne L. monocytogenes to antibiotics. L. monocytogenes
was isolated and molecularly characterized using polymerase chain reaction (PCR) from 17 RTE
vegetable samples. The confirmed L. monocytogenes was further assessed for phenotypic and genotypic
antibiotic resistance using the disc diffusion test and PCR primers targeting six antibiotic classes and
thirty-one related antibiotic resistance genes (ARGs), respectively. The results revealed that Listeria
counts ranged from 1.60 to 3.44 log10 CFU/g in the samples. The isolates exhibited high resistance
against penicillin G, erythromycin, vancomycin, tetracycline, trimethoprim-sulfamethoxazole, and
nitrofurantoin among the 108 isolates tested. A total of 71 multiple antibiotic resistance (MAR)
phenotypes were observed in the isolates, which ranged from resistance to 3 to 13 antibiotics. The
MAR index was >0.2 in 97% of the isolates. Some of the highly detected ARG subtypes included
SulI (100%), TEM (76.9%), tetA (59%), and tetM (54.7%). The findings show a high occurrence of
multidrug-resistant L. monocytogenes and clinical ARGs in fresh vegetables, which constitutes an
immediate danger for the health security of the public.