Use of invA Gene Specific PCR Analysis for the Detection of Virulent Salmonella Species in Beef Products in the North West Province, South Africa

Abstract

A total of 32 beef samples were collected from shops around the North West Province, South Africa and analyzed for the presence of Salmonella species. A total of 96 presumptive isolates were screened for characteristics of Salmonella. All (100%) of the isolates were Gram negative rods and catalase positive. However, only a small proportion (25%) utilized citrate as a sole carbon source while 78% of the isolates fermented the sugars glucose, lactose and sucrose. Gas was produced by 34.4% while only 3.1% of these isolates produced hydrogen sulphide gas. Despite the fact that a small proportion (12.5%) of these isolates were identified as Salmonella species by the API 20E test, a much larger proportion agglutinated with Salmonella Poly A-S antiserum (53.1%) when compared to the Salmonella Poly O antiserum. To avoid bias, all the 96 isolates were screened for the Salmonella specific invA gene through PCR analysis and only 10 (10.4%) isolates were positively identified. Moreover, none of the isolates possessed the fliC flagella gene while a small proportion 11(11.5%) were positive for the fljB gene fragments. The presence of these pathogenic Salmonella species in raw meat indicates the health risk that these food products can cause to consumers, especially if consumed undercooked.