If there is evidence of a common-source outbreak, questions concerning the ingestion of specific foods and the timing of diarrhea after a meal can provide clues to the bacterial cause of the illness.

• Staphylococcus aureus: Enterotoxin is elaborated in food left at room temperature (e.g., at picnics).
  • - The incubation period is 1-6 h. Disease lasts <12 h and consists of diarrhea, nausea, vomiting, and abdominal cramping, usually without fever.
  • - Most cases are due to contamination from infected human carriers.
• Bacillus cereus: Either an emetic or a diarrheal form of food poisoning can occur.
  • - The emetic form presents like S. aureus food poisoning, is due to a staphylococcal type of enterotoxin, has an incubation period of 1-6 h, and is associated with contaminated fried rice.
  • - The diarrheal form has an incubation period of 8-16 h, is caused by an enterotoxin resembling Escherichia coli heat-labile toxin (LT), and presents as diarrhea and abdominal cramps without vomiting.
• Clostridium perfringens: Ingestion of heat-resistant spores in undercooked meat, poultry, or legumes leads to toxin production in the intestinal tract. The incubation period is 8-14 h, after which pts develop ≤24 h of diarrhea and abdominal cramps, without vomiting or fever.