Differences in transcription and expression of staphylococcal enterotoxin C in processed meat products

Staphylococcus aureus is a major foodborne pathogen contaminating meat products where it is able to produce thermostable enterotoxins. Staphylococcal enterotoxin C (SEC) together with other classical toxins are the most frequently detected enterotoxins associated with staphylococcal food poisoning (SFP) outbreaks. This study investigated the transcription and formation of SEC in four heat-processed meat products: chicken ham, pork ham, pepper beef salami and turkey ham. Meat samples were inoculated with four SEC producing strains of S. aureus individually at a level of approximately 5 log CFU/cm2. The expression and production of SEC was examined during the growth of S. aureus in meat compared to routinely used laboratory media. Results indicate that the expression of sec in meat products varied significantly and was dependent upon the different levels of fat content compared to the laboratory medium. Meat varied in salt content and pH and this influences SEC production. Increased SEC and sec expression was observed in chicken and pork ham and was approx. 24-35 times higher compared with other meat products. Lower levels of sec expression and SEC production were found in turkey ham with SEC concentration 378 times lower than in chicken ham at 72 h. The varying meat environment affected the transcription and formation profiles of SEC, however staphylococcal growth remained reasonably constant. Staphylococcal strains were able to produce quantities of SEC under room temperature conditions that would be sufficient to cause food poisoning in susceptible individuals (mainly in children). Our data is important with respect to food contamination by S. aureus and contributes to an improved understanding of SEC production capabilities of these pathogens in meat containing food products.