Staphylococcus aureus and enterotoxin A relative gene expression in beef meat after lactic acid treatment and storage at different temperatures

Abstract

The Staphylococcus aureus enterotoxin A (sea) is the toxin mostly involved in Staphylococcus aureus (S. aureus) food poisoning. In this study, the effect of different lactic acid (LA) concentrations (LA 1% and 2%) and temperatures (4 oC, 25 oC, and 37 oC) on S. aureus growth and relative sea expression in fresh meat cuts were studied. Real-Time RT-PCR used to determine the relative sea expression. Fresh meat cuts were inoculated with 105 CFU/g of S. aureus producing enterotoxin A. S. aureus growth and relative sea expression were regularly tested for 48 hours. The growth of S. aureus was decreased by one log CFU/g than control sample using 1% LA and 2% LA 2% (5.32 ± 3.76 log CFU/g, 4.38 ± 3.00 log CFU/g and 4.54 ± 3.18 log CFU/g respectively) at zero time. Relative expression of the sea gene in both LA concentrations was lower than control. Moreover, both lactic acid concentrations had effect on relative sea gene expression at all examined hours, especially at 4 oC compared to control samples. The higher the lactic acid concentration, the lower the S. aureus enterotoxin A relative expression was.