Inhibitory effect of acetic acid on the toxicity of Staphylococcus aureus and its membrane vesicles.

Staphylococcus aureus is a bacterium present on the human skin and produces enterotoxins (SEs) when it grows in food, resulting in toxin-type food poisoning. The SEs and virulence factors from S. aureus, which are considered encapsulated and concentrated in membrane vesicles (MVs) composed of the bacterium's own cell membrane, reach host target cells and trigger inflammation. This study was conducted to investigate the effects of acetic acid, used as a food additive, on the expression of virulence factors and MV-induced inflammation in S. aureus. Results showed that 40 mM acetic acid inhibited the production of staphylococcal enterotoxin A (SEA). When S. aureus was cultured in broth containing 40 mM acetic acid, the levels of SEA and several cargo proteins in generated MVs reduced. MVs prepared by adding acetic acid also reduced the expression levels of inflammation-related genes in immortalized human keratinocytes. Therefore, acetic acid may inhibit staphylococcal food poisoning and inflammation by altering the properties of MVs from S. aureus.