Four hours after eating ham sandwiches kept unrefrigerated at a picnic, three people develop sudden severe vomiting with abdominal cramps. There is no diarrhoea and no fever, and all recover within 24 hours. The pathogenesis involves:

• A Invasion of intestinal epithelium by live bacteria ingested with the food
• B Toxin produced after germination of spores inside the gut lumen
• C A preformed heat-stable enterotoxin acting on vagal receptors and the vomiting centre ✓
• D Shiga-like toxin inhibiting the 60S ribosomal subunit

Explanation

Short incubation (1 to 6 hours) with vomiting as the dominant symptom, absence of fever, and rapid recovery are classic for Staphylococcus aureus food poisoning caused by preformed heat-stable enterotoxins that stimulate the vagus and medullary vomiting centre. Ingested organisms are killed by gastric acid and play no role. Spore germination in the gut describes Clostridium perfringens, whose illness is diarrhoeal with a longer incubation.

Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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