Antibiotic-Resistant Bacteria isolated from Fresh Organic Vegetables Sourced from Local Producers in Eastern Spain

Antibiotic resistance (AMR) is a critical issue within the "One Health" approach, which encompasses human and animal health, agriculture, and environmental waste management. Fresh vegetables, which are frequently consumed raw, may contribute to the spread and transmission of AMR. Therefore, the aim of this research was to study the microbiological quality and prevalence of ARB and ARG in fresh vegetables.

Twenty-one samples were purchased directly from organic farms in Valencia (Spain), and two soil samples were taken from the cultivation sites. Samples were examined for total viable bacteria, coliforms, Escherichia coli, Listeria monocytogenes and Salmonella spp. Isolation was performed onto culture media supplemented with cefotaxime and meropenem.

A total of 122 strains were isolated. A total of 24 Gram-negative isolates were selected and identified by biochemical tests and sequencing of 16S rRNA. Their sensitivity to 15 antibiotics was determined, and PCR assays were performed for main expanded spectrum beta-lactamase (ESBL), carbapenemase- and plasmid-mediated quinolone resistance genes, both for the samples and for the isolates.

Overall, 96% of the samples showed total viable bacteria levels over the accepted 10(5) cfu/g standard limit, and 87% showed coliforms levels over the accepted 10(4) cfu/g standard limit. In two samples (9%), E. coli levels were not acceptable. Salmonella and L. monocytogenes were not detected.

Seventy-nine percent of the isolates were resistant to at least one antibiotic, and 50% were ESBL productors. PCR showed the presence of bla_CMY-2 (13%), bla_TEM (8%), bla_SHV (4%), bla_OXA-48 (17%), bla_KPC (8%), bla_IMP (4%), qnrA (17%), qnrB (21%) and qnrS (8%) genes.

The detection of carbapenems resistance genes is particularly concerning because it poses a serious risk for immunocompromised patients. Thus, fresh organic vegetables harboring ARB and ARG constitute a potential risk to consumers. Further studies must be done to detect ARG and how they propagate in non-medical environments.