Retail foods as reservoirs for carbapenemase-producing, multidrug-resistant Klebsiella spp harboring virulence genes in Mexico

Foodborne diseases are a global public health concern traditionally associated with classical enteric pathogens such as Escherichia coli, Salmonella spp, and Listeria monocytogenes . Increasing evidence, however, indicates that foods may also serve as reservoirs and transmission vehicles for opportunistic pathogens of clinical relevance, including members of the Klebsiella pneumoniae species complex (KpSC). In this study, Klebsiella isolates recovered from retail food samples in Sonora, Mexico, were characterized. Twenty-eight isolates were molecularly affiliated with the KpSC by PCR and analyzed for virulence traits, biofilm formation, hypermucoviscosity, antimicrobial resistance profiles, and resistance-associated genes. Virulence markers were common, with traT (50%) and fimH (43%) being the most prevalent. A hypermucoviscous phenotype was observed in 29% of isolates, and all isolates produced biofilms, with 79% classified as strong biofilm producers. All KpSC-affiliated isolates were multidrug-resistant; 32% met criteria for extensive drug resistance, and one isolate was classified as possibly pandrug-resistant. High resistance rates were observed against multiple antimicrobial classes, including β-lactams and fosfomycin (89%), a last-resort agent for carbapenem-resistant Klebsiella . Although only one isolate displayed a phenotypic extended-spectrum β-lactamase profile, no ESBL-associated genes were detected. Importantly, two food-derived isolates were phenotypically confirmed as carbapenemase producers and carried the metallo-β-lactamase gene bla NDM-1 . These findings indicate that retail foods may harbor KpSC lineages carrying combinations of virulence traits and clinically critical antimicrobial resistance determinants. While Klebsiella spp are not classical foodborne pathogens, their presence in foods underscores the food chain as a reservoir for dissemination of opportunistic pathogens, reinforcing surveillance under a One Health framework