Thesis (Ph.D.) - Cairo University - Faculty of Veterinary Medicine - Department of Food Hygiene and Control

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%), lysozyme concentrations (100 mg/ml and 200 mg/ml) and temperatures (4{u00B0}C, 25oC, and 37{u00B0}C) on S. aureus growth and relative sea expression in fresh meat cuts were studied. Real-Time PCR (RT-PCR) was used to determine relative sea expression. Fresh meat cuts were inoculated with 105 CFU/g of S. aureus producing enterotoxin A. Thus, 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 (5.32 ± 3.76 log CFU/g, 4.38 ± 3.00 log CFU/g and 4.54 ± 3.18 log CFU/g respectively) while, the use of 100 mg/ml and 200 mg/ml lysozyme decreased the counts to be 4.95 ± 3.77 log CFU/g and 4.98 ± 3.99 log CFU/g, respectively. Relative expression of the sea gene in both lysozyme and LA concentrations was lower than control. Moreover,both lactic acid and lysozyme concentrations had an effect on relative sea gene expression at all examined hours, especially at 4{u00B0}Ccompared to control samples.The higher the lactic acid concentration, the lower the S. aureus enterotoxin A relative expression was, lysozyme as well

Issued also as CD