DETECTION OF PATHOGENIC AND VIRULENT SEROGROUPS OF LISTERIA MONOCYTOGENES IN BEEF PRODUCTS POSES A HEALTH CONCERN TO CONSUMERS IN SOUTH AFRICA

Abstract

In 2017-18 South experienced the largest outbreak of human listeriosis in the world caused by L. monocytogenes following the consumption of ‘polony’, a ready-to-eat meat product. A majority (59%) of the cases originated from Gauteng province, South Africa. As a follow-up study to the outbreak, a study was carried out to determined the prevalence of pathogenic and virulence serogroups of L. monocytogenes in various beef and beef products retailed in Gauteng province, South Africa using standard bacteriological and molecular methods. The overall prevalence of Listeria spp. was 28.0% (112/400), comprising Listeria monocytogenes (9.3%), Listeria innocua (16.3%), and Listeria welshimeri (2.5%) (p<0.001). It is crucial to have detected that the region (p=0.036), type of product (p=0.032), and temperature at storage (p=0.011) significantly affected the occurrence of L. monocytogenes in beef products. The pathogenic serogroups 4b-4d-4e (51.4%), and 1/2a-3a (43.2%), were detected among the isolates of L. monocytogenes, and importantly, they were all carriers of seven virulence-associated genes (hlyA, inlB, plcA, iap, inlA, inlC, and inlJ). Our study also demonstrated that 16.7% of ‘polony’ samples investigated were contaminated by L. monocytogenes. Considering that pathogenic and virulent L. monocytogenes contaminated beef and beef products retailed in South Africa, the food safety risk posed to consumers still exists and cannot be ignored. Therefore, it is imperative to reduce the contamination of these products with L. monocytogenes during beef production, processing, and retailing to avoid future outbreaks of human listeriosis in the country.