Abstract:The phenotypic, biochemical, and genetic characteristics of an emerging food-borne multidrug-resistant atypical enteropathogenic Escherichia coli (aEPEC) strain were explored. An extended-spectrum β-lactamase (ESBL)-producing atypical aEPEC strain, E2892A1, carrying the plasmid-mediated colistin resistance gene mcr-1 was isolated from retail food. The biochemical characteristics were analyzed using the Analytical Profile Index 20E test. The minimal inhibitory concentrations of antibiotics were determined using the microbroth dilution method. Further, the genetic characteristics (antibiotic resistance genes, plasmid replicon types, and virulence genes) were analyzed using whole-genome sequencing (WGS), and the genetic evolutionary relationship was constructed based on core genome single nucleotide polymorphism cluster analysis. The results indicated that the aEPEC E2892A1 strain had a high prevalence of resistance to ceftazidine, ceftriaxone, tetracycline, ampicillin, and other commonly used antibiotics and was an ESBL-producing strain. WGS results showed that the strain was an aEPEC and carried 17 antibiotic-resistance genes, the virulence gene eae, and four plasmid replicon subtypes. This is the first report of multiple resistance genes (especially CTX-123 and mcr-1) co-existing in the same ESBL-producing aEPEC ST752 strain. Conjugation experiments confirmed that the mcr-1 gene could be transmitted horizontally to E. coli C600. The presence of such a strain in food poses a potential health threat to humans. Thus, continuous attention to its spread is essential. This study provides important basic data for monitoring the risk of highly virulent multidrug-resistant bacteria in food, which can aid the rational use of antibiotics and the formulation of clinical protocols for the treatment of food-borne diseases.
