Contamination of retail foods, particularly Turkey, from community markets (Minnesota, 1999-2000) with antimicrobial-resistant and extraintestinal pathogenic Escherichia coli

To assess the food supply as a possible vehicle for antimicrobial-resistant and extraintestinal pathogenic Escherichia coli (ExPEC), we defined the prevalence, density, clonal diversity, virulence characteristics, and antimicrobial resistance profiles of E. coli among diverse retail food items. A microbiological survey was undertaken of 346 food items (vegetables, produce, beef, pork, chicken, and turkey) purchased as a convenience sample from 16 retail markets within the Minneapolis-St. Paul area in 1999-2000, with selective cultures for E. coli and extensive molecular and phenotypic characterization of E. coli isolates. Meats, particularly turkey products, were often extensively contaminated with antimicrobial-resistant E. coli and ExPEC, to a much greater extent than were produce items, even those from farmer's markets. Moreover, meat-source E. coli differed substantially from produce-source E. coli with respect to phylogenetic background (more commonly from virulence-associated phylogenetic groups B2 or D), virulence genotype (more extensive), and antimicrobial resistance profile (more extensive). Molecular typing methods matched four turkey-source isolates to selected human clinical and fecal isolates representing the O7:K1:H-, O83:K1, and O73/O77:K52:H18 ("clonal group A") clonal groups of ExPEC. Meats purchased in grocery stores, particularly turkey products, are frequently contaminated with antimicrobial-resistant E. coli and ExPEC. Further study is needed regarding the origins and health consequences of these foodborne organisms, both to clarify the need for and to guide the possible development of appropriate regulatory and monitoring systems and preventive interventions.