Effect of temperature and pH on growth of Staphylococcus aureus in co-culture with Lactococcus garvieae.

Staphylococcus aureus growth and enterotoxin production in co-culture with Lactococcus garvieae were studied in laboratory medium as a function of incubation temperature and pH values. Doehlert experimental design was used to study the effect of L. garvieae concentration, temperature, and pH on S. aureus growth in laboratory medium. The mathematical model obtained was validated in cheeses. The inhibition of S. aureus growth by L. garvieae was more important during the first 6 hours of incubation, and its effect increased when its concentration increased. After 24 and 48 hours, the effect of L. garvieae decreased, and the growth of S. aureus was positively influenced by higher temperature and pH values. Staphylococcal enterotoxins were detected in only one experimental set after 48 hours of incubation at 30 degrees C at pH 6.8. Our results argue in favor of adding antagonist strain early in the cheese-making process.