Temperature dependence of the production of staphylococcal enterotoxin A by Staphylococcus aureus

We incubated 11 strains of Staphylococcus aureus in a brain heart infusion broth at 10-37 °C with two inoculum sizes and examined their enterotoxin A (SEA) production by a Western blot analysis to clarify the effect of incubation temperature on SEA production. Although SEA was detected in the exponential phase at 15-37 °C, it was also detected in the stationary or death phase at 10 °C. The maximal SEA concentrations of most strains increased as the temperature was increased, although some strains produced as much at 15 °C and 20 °C as they did at 37 °C. The maximal SEA concentration was definitely lowest at 10 °C, and as the temperature was increased, the production rate increased. However, a relationship between the production rates at the two different temperatures was not apparent. Some strains produced more SEA at 10-20 °C with a smaller inoculum size than with a larger one. SEA production therefore did not necessarily depend on the incubation temperature, and it would be difficult to predict at 10 °C and 15 °C from the production at 37 °C.