Detection of Pathogenic Serogroups and Virulence Genes in Strains Isolated from Beef and Beef Products Retailed in Gauteng Province, South Africa, Using Phenotypic and Polymerase Chain Reaction (PCR)-Based Methods.

South Africa recently (2017-18) experienced the largest outbreak of human listeriosis in the world caused by following the consumption of "polony," a ready-to-eat meat product. Most (59%) cases originated from Gauteng province, South Africa. As a follow-up study to the outbreak, we used standard bacteriological and molecular methods to determine the prevalence of pathogenic and virulent serogroups of in various beef and beef products retailed in Gauteng province, South Africa. The overall prevalence of spp. was 28% (112/400), comprising (9.3%), (16.3%), and (2.5%) ( < 0.001). It is crucial to have detected that the region (=0.036), type of product (=0.032), and temperature at storage (=0.011) significantly affected the occurrence of in beef products. It is alarming that pathogenic serogroups 4b-4d-4e (51.4%) and 1/2a-3a (43.2%) were detected among the isolates of . Importantly, they were all carriers of seven virulence-associated genes (). Our study also demonstrated that 16.7% of "polony" samples investigated were contaminated with Considering that pathogenic and virulent contaminated beef and beef products retailed in South Africa, the food safety risk posed to consumers remains and cannot be ignored. Therefore, it is imperative to reduce the contamination of these products with during beef production, processing, and retailing to avoid future outbreaks of human listeriosis in the country.