What is the infectious agent of Staphylococcus aureus?

• A. Bacteria themselves cause disease directly
• B. Enterotoxins produced in food by Staphylococcus aureus
• C. Viral particles
• D. Endotoxins from Gram-negative bacteria

Answer: (B)

In Staphylococcus aureus food poisoning, the illness is caused by toxins that the bacteria produce in food, not by the live bacteria infecting tissues. The infectious agent here is the enterotoxin itself—preformed in the food—that, once ingested, triggers vomiting and abdominal cramps. These enterotoxins are heat-stable, so they can cause illness even if the food has been cooked afterward. While the bacteria may contaminate food, the disease mechanism is toxin-mediated rather than direct bacterial invasion. Viral particles aren’t involved, and endotoxins from Gram-negative bacteria don’t apply, since this illness centers on enterotoxins produced by a Gram-positive organism.