Prevalence of Staphylococcus aureus and staphylococcal enterotoxins in rawpork and uncooked smoked ham - a comparison of classical culturing detection and RFLP-PCR

In many countries Staphylococcus aureus is considered to be the second or t hird most common pathogen causing outbreaks of food poisoning, only outnumb ered by Salmonella spp. and in competition with Clostridium perfringens. Of ten the consumption of ham or meat containing staphylococcal enterotoxins ( SE) is identified as cause of the illness. Thus, to gain an insight into th e prevalence of S. aureus and its emetic enterotoxins in raw pork and uncoo ked smoked ham and to investigate how the prevalence of the pathogen is inf luenced during the fabrication process, a total of 135 samples of raw pork, salted meat and ready-for-sale uncooked smoked ham were examined for the p revalence of S. aureus and staphylococcal enterotoxins A to D (SEA-SED). To this means classical cultural methods were employed as well as molecular b iological techniques (PCR) and the results were compared. In 25.9% of all samples S. aureus was detected by culture whereas 51.1% of the samples showed a positive result when PCR was used for the detection of the pathogen. Fresh meat was contaminated most often. By PCR, 62.2% were i dentified as being S. aureus positive compared to 57.7% positive samples us ing the cultural technique. The detection rate during the fabrication proce ss declined significantly. The pathogen was cultivated from 8.9% of the sal ted meat samples. Here, 55.6% of the samples reacted positively in the PCR, and finally, in approximately a third of the ready-for-sale smoked hams, S . aureus genes were found. From 11.1% of these samples, the pathogen could be isolated by culture. From these results, we conclude that the PCR used i n this study is more sensitive than the classical cultural method. By PCR, one or more staphylococcal enterotoxim genes were found in 24 of th e 135 examined samples. This means that 34.8% of the staphylococcal strains identified using the PCR technique were enterotoxigenic. Using the SET-RPL A, a percentage of 28.6% enterotoxigenic isolates was ascertained. No staph ylococcal enterotoxin formation was detected by the SET-RPLA in ready-for-s ale ham, although SE-genes were found by PCR. The detection of SE-genes by PCR is faster and easier to perform than the SET-RPLA. (C) 2001 Elsevier Sc ience B.V. All rights reserved.