Abstract:

Objective: To explore the inhibitory effect of six food antiseptics (nitrite, sodium benzoate, ε-polylysine, chitosan,
polyphenols, and nisin) on the growth of Staphylococcus aureus SA003, a strain capable of causing food poisoning, as well
as on the expression of enterotoxin genes by this strain at the mRNA level. Methods: According to the national standard (GB
2760—2014) concentration limits, aqueous solutions of six different preservatives were prepared and added into TSB medium
inoculated with about 105 CFU/mL of S. aureus SA003. All cultures were shaken at 150 r/min at 37 ℃. After 24 h, the colonies
of the cultures treated by different preservatives were counted, respectively. At the same time, the cells were collected for RNA
extraction and reverse transcription. The fluorescence quantitative PCR was used to detect the relative expression level of each
enterotoxin gene at the mRNA level. Results: At the GB maximum concentration limits, the inhibitory effects of different additives
on the growth of S. aureus SA003 were nisin > polyphenols > chitosan > ε-polylysine > sodium benzoate > nitrite. All six
preservatives could inhibit the expression of sea, sed, seg, sei, selj, selm, selr and selu genes at the transcriptional level and
their effects were significantly different. Conclusion: Adding preservatives in liquid medium not only inhibited the growth of
S. aureus, but also significantly reduced the expression of staphylococcal enterotoxin genes.

Key words: food antiseptics, Staphylococcus aureus, enterotoxin genes, expression