Comprehensive Study of the Boundaries of Enterotoxin A Production and Growth of Staphylococcus aureus at Various Temperatures and Salt Concentrations

Staphylococcus aureus food poisoning, which is still a serious health problem worldwide, is caused by the intoxication of staphylococcal enterotoxin (SE). Among many types of SE, staphylococcal enterotoxin type A (SEA) is known to be the most responsible for S. aureus food poisoning worldwide. Several researchers have reported the modeling of growth/no growth boundaries for S. aureus with a logistic regression model. In this study, the boundaries of SEA production and S. aureus growth in broth were first performed with the logistic regression model, to evaluate the effects of environmental factors of temperature and salt. Consequently, the boundaries of SEA production and growth of S. aureus in temperature and salt concentration could be produced with the model in shaking and stationary cultures. The area where S. aureus cells would grow, but not produce SEA could be shown between the boundaries of SEA production and growth. Internal and external validations showed that the model could well describe and predict experimental results. Further, the maximum concentrations of SEA and cell population under various conditions of temperature and salt concentration were also compared between the shaking and stationary cultures. These results obtained in this study would become useful information in food industry to prevent S. aureus food poisoning outbreaks. PRACTICAL APPLICATION: Production/no production of staphylococcal enterotoxin A at various temperatures and salt concentrations in shaking and stationary cultures could be estimated well with a logistic regression model. Growth/no growth of staphylococcal cells under the same conditions was also well estimated with the model. The area where S. aureus cells would grow, but not produce SEA could be shown with the model. This present analysis would provide useful information in food industry to prevent staphylococcal food poisoning outbreaks.