Antimicrobial resistance, virulence and genetic diversity of Escherichia coli from a hospital food service

Background: Escherichia coli is an indicator of food contamination and an important public health pathogen with high ability to acquire virulence and antimicrobial resistance. The presence of potentially pathogenic strains in the food chain poses a high risk to consumers, particularly in highly vulnerable environments such as hospitals. This study aims to investigate the antimicrobial resistance profiles, molecular typing, virulence and integrons of fifteen E. coli isolates recovered from a hospital kitchen.

Material and methods: Fifteen E. coli strains were isolated from different raw foods (n=10) and processing areas (n=5) in a hospital kitchen. Molecular typing was assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Antimicrobial susceptibility and phenotypes of ESBL, AmpC, and carbapenemase were tested by disc diffusion methods. The molecular characterisation (serotype, phylogeny, virulence factors and presence of integrons) was performed by PCR.

Results: Eleven PFGE patterns and ten sequence types (STs) were identified among the fifteen isolates, which included high-risk clones belonging to ST10 Cplx (ST10, n=1) and ST155 Cplx (ST58, n=1). No O25a, O25b or O157 serotypes were detected. Phylogroups were distributed as A (n=4), B1 (8), B2 (2), and E (1). Antimicrobial resistance analysis determined that 47% were multidrug resistant strains. Four strains were ESBL producers associated with the bla_SHV-12 gene, four strains showed an AmpC phenotype, and no carbapenem-resistant E. coli was observed. Class 1 integrons were detected in 20% of isolates, carrying dfrA1–aadA1 or dfrA12–gcuF–aadA2 arrangements. Concerning virulence-associated factors, all isolates were positive for the fimA gene, and 53% of the isolates carried the aer gene.

Conclusions: The high genetic diversity, the presence of antimicrobial resistance and virulence determinants among E. coli isolates from a hospital food service environment underscore a potential threat to food safety and public health.