Molecular surveillance of foodborne bacterial pathogens and resistome in food products from Hong Kong

Foodborne infections pose an increasing public health challenge worldwide. The problem has been aggravated by dissemination of antimicrobial resistance genes among zoonotic pathogens, which results in a sharp increase in antibiotic resistance rate recorded among the major foodborne pathogens. To obtain an overview of the extent by which food products purchased in the markets in Hong Kong was contaminated by foodborne pathogens, we collected 95 raw meat samples from wet markets and isolated 236 bacterial strains of various species, with Escherichia coli being the most dominant species (131 strains). Contamination of food products by multiple foodborne pathogens was commonly observed. These include both Gram-positive and negative bacteria that exhibit various level of resistance, with some possessing multiple clinically important antibiotic resistance genes. Seventeen bacterial strains of various species isolated from three food samples were comprehensively analysed by the Oxford Nanopore R10.4 technology. Novel conjugative plasmids carrying antimicrobial resistance genes-bearing mobile genetic elements were commonly detectable in the test strains. Some of the plasmids were shown to be originated from other environmental sources or other bacterial species, indicating that raw foods in the local market may serve as a reservoir of resistance-encoding genetic elements from which such elements are disseminated to various microbial pathogens. These findings suggest a need to perform periodic but comprehensive surveillance of multidrug resistant bacterial pathogens and the major antimicrobial resistance genes in common food products, so as to disrupt the transmission routes of such organisms and the resistance-encoding genetic elements that they harbor.