Sodium nitrite and staphylococcal enterotoxin C in lab strains
What it found
In lab tests, sodium nitrite increased the mRNA for staphylococcal enterotoxin C in five of seven S. aureus strains, but protein levels did not always rise.
Some strains made less toxin.
What they found
Animal and lab studies
mRNA transcription
In lab tests, five of seven S. aureus strains had higher sec mRNA levels under nitrite stress in at least one growth phase. Two bovine strains showed no significant change.
Protein levels
SEC protein did not always match the mRNA increases. Some strains made more protein, but others made less, and the timing varied.
Regulatory genes
In one high-producing strain, removing the agr gene lowered sec mRNA under both normal and nitrite conditions. Removing sigB gave opposite effects under nitrite stress compared to normal conditions.
Defective agr
One strain had a broken agr gene but still produced normal amounts of SEC, suggesting other regulatory pathways are involved.
Different toxins
The authors note that other enterotoxins like SEB and SED respond differently to nitrite, so each toxin may react in its own way.
What the authors conclude
“Based on these findings, addition of nitrite to food, therefore, does not contribute to lower SEC levels and could even pose a potential threat to consumers by elevating SEC levels.”
Also in their conclusions
- They conclude that nitrite does not lower SEC levels and could even increase them in some strains.
- They say that more knockout experiments are needed to fully understand the regulatory networks.
- They call for their results to be verified in a suitable food model.
How it was done
The authors wanted to see if nitrite, used in cured meats, affects the production of staphylococcal enterotoxin C, a common cause of food poisoning. They note that limiting nitrite could increase toxin levels.
They grew seven strains of Staphylococcus aureus in lab medium with and without 150 mg/l sodium nitrite, and measured sec mRNA and SEC protein at 4, 10, and 24 hours. They also tested knockout mutants of one high-producing strain to see which regulatory genes were involved.
What it can’t tell you
- These are lab experiments with bacterial cultures, not people or actual food products.
- The study cannot show whether the same changes in toxin production would happen in real cured meats or in the human body.
- It does not measure whether eating nitrite-cured meat would make people sick.
Who paid
- Authors work at
- University of Zurich, Switzerland; Institute for Food, Switzerland
The paper
- Title
- Nitrite stress increases staphylococcal enterotoxin C transcription and triggers the SigB regulon
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Cite
- Etter D, Büchel R, Patt T, et al (2022). Nitrite stress increases staphylococcal enterotoxin C transcription and triggers the SigB regulon. FEMS microbiology letters. doi:10.1093/femsle/fnac059Free full textPubMed 35883216DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error