Effect of sodium nitrite and regulatory mutations Δagr, ΔsarA, and ΔsigB on the mRNA and protein levels of staphylococcal enterotoxin D

Research output: Contribution to journalArticle


Staphylococcal food poisoning results from ingestion of enterotoxins produced by Staphylococcus aureus. Staphylococcal enterotoxin D (SED) is one of the most common toxins detected in S. aureus strains associated with intoxications. The effect of sodium nitrite on enterotoxin production has been only partly investigated, despite its wide usage in meat products. In addition, the factors influencing SED regulation are unclear. The aim of this study was to determine the effect of sodium nitrite on sed transcription and SED production, as well as the effect of regulatory mutations on SED protein levels. Temporal sed mRNA and SED protein levels were compared in LB and LB supplemented with 150 mg/L nitrite, and SED protein levels between wild type (wt) and isogenic regulatory mutants (Δ. agr, Δ. sarA, Δ. sigB) under control and sodium nitrite conditions. Relative sed mRNA levels of wt strains were higher in late stationary phase in the presence of nitrite compared to control conditions. However, SED protein levels were decreased in the presence of nitrite. In LB, Δ. agr mutants showed SED levels similar to the wt, while Δ. sarA mutants exhibited reduced and Δ. sigB mutants increased SED levels compared to the wt. In LB with sodium nitrite, SED levels of mutant strains were reduced similar to the wt strains, except for two Δ. agr mutants, in which SED levels were increased in the presence of nitrite. Overall, strain-specific variation with regard to the effect of regulatory mutations was observed. In addition, the data suggests that SED regulation may not be as tightly dependent on Agr as previously described.


External organisations
  • University of Zurich
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Food Science


  • Enterotoxin D formation, Regulatory response, Sed expression, Sodium nitrite, Staphylococcus aureus
Original languageEnglish
Pages (from-to)37-45
Number of pages9
JournalFood Control
Publication statusPublished - 2016 Jul 1
Publication categoryResearch

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