Reduced Enterotoxin D Formation on Boiled Ham in Staphylococcus Aureus Δagr Mutant

Staphylococcal food poisoning (SFP) is a common cause of foodborne illness worldwide, and enterotoxin D (SED) is one of the most frequent enterotoxins associated with it. It has been reported that the expression and formation of SED in is regulated by the quorum sensing Agr system. In this study, the effect of deletion on expression in grown on boiled ham was investigated. Growth, mRNA and SED protein levels in an wild type strain and its isogenic Δ mutant were monitored for 14 days at 22 °C. The results showed that although deletion of the gene did not affect the growth rate or maximum cell density of on boiled ham, it had a pronounced effect on SED formation during the first 5 days of incubation. The SED concentration was not reflected in the amount of preceding transcripts, suggesting that transcription levels may not always reflect SED formation. The expression of RNAIII transcript, the regulatory signal of the Agr system, was also monitored. Similar transcription patterns were observed for RNAIII and . Surprisingly, in the Δ mutant, expression was comparable to that in the wild type strain, and was thus unaffected by deletion of the Agr system. These results demonstrate that the Agr system appears to only partially affect SED formation, even in a real food environment.