Staphylococcal enterotoxin synthesis during the exponential, transitional, and stationary growth phases

Small inocula (1 to 10 colony-forming units per ml of broth) of Staphylococcus aureus strains S-6, S-6R, and FRI-100 were employed to study growth and enterotoxin synthesis in 4% protein hydrolysate powder broths. For each strain, the exponential growth phase ended once the population approached 10(9) to 2 x 10(9) colony-forming units per ml. By that time, the concentrations of enterotoxins A and B reached the minimal level (1 to 2 mug/ml) at which the single gel diffusion tube method becomes applicable. By microslides and reverse passive hemagglutination, enterotoxins A and B were found to be synthesized during the exponential growth phase, but at different exponential rates.