Wedding Feast Outbreak in Tirupati
At a wedding in Tirupati, 180 guests eat a buffet. Within 2–6 hours, 47 develop severe vomiting, abdominal cramps and mild diarrhoea; 9 are hospitalised. The menu included chicken biryani cooked at 11:00 and held in insulated boxes at 38–42°C until 14:30, paneer curry, boiled rice and a milk-based sweet. The bride's family also reports that three kitchen workers had skin lesions on the hand. Stool samples from 12 patients are sent, but the laboratory can only culture and do conventional identification; no food remains except 200 g of biryani and 100 g of sweet. An FSO arrives at 18:00 and finds no temperature logs, a hand-wash sink without soap, and the sweet kept in the same box as raw eggs. The laboratory later reports Staphylococcus aureus from one stool and Bacillus cereus from the biryani, both at low counts. The FSO must decide whether to close the kitchen, what to sample, and how to interpret the results.
1. Rank the likely causative agents and explain how incubation period and symptom pattern should guide the investigation.
Read the worked answer
The short incubation of 2–6 hours with vomiting dominating points first to a preformed toxin. Staphylococcus aureus is the leading hypothesis because of the rapid onset, vomiting, hand lesions in food handlers and a milk-based sweet that could support toxin production if held warm. Bacillus cereus emetic type is a strong second because boiled rice and biryani held at 38–42°C provide a classic setting, and the emetic toxin also acts within 1–6 hours. Clostridium perfringens is less likely because it usually causes diarrhoea after 8–16 hours, not early vomiting. The stool culture results must be interpreted cautiously: S. aureus in one stool does not prove enterotoxin was formed in the food, and low-count B. cereus in biryani does not prove a foodborne dose. The investigation should rank hypotheses by epidemiological consistency, not by which organism was easiest to culture.
2. Design the sampling and laboratory testing plan, including quantitative counts and toxin detection, and explain how you would interpret low counts.
Read the worked answer
Sample the remaining biryani and sweet separately, plus any retained ingredients, water, and hand-swab or lesion samples from the three workers. Collect early vomit and stool where possible. Transport all food samples at 4–8°C, without preservatives, and record times. Ask the laboratory for quantitative S. aureus and B. cereus counts, not just presence/absence, and for staphylococcal enterotoxin detection in the sweet and biryani. B. cereus emetic toxin can be sought if available. Interpret counts against the food matrix and the clinical picture: S. aureus at ≥10^5 CFU/g, or enterotoxin, is meaningful; B. cereus at ≥10^5 CFU/g supports the emetic syndrome. Low counts in stool are expected and prove little. A negative food result does not exclude an outbreak if the food was consumed or discarded; the epidemiological link and short incubation still matter. The report should state that low-level growth may reflect post-outbreak handling, not the dose ingested.
3. What immediate control and enforcement actions are justified, and what should be avoided?
Read the worked answer
Immediate action should focus on stopping further exposure and removing infected workers from food handling. The kitchen should be suspended from catering until it demonstrates safe holding temperatures, hand-wash facilities with soap, separation of raw eggs from ready-to-eat sweets, and a written food-safety plan. The three workers with lesions should be excluded from food handling until medically cleared. A general closure of the entire venue may be disproportionate if the problem is confined to the caterer. The FSO should record the buffet holding times, take samples, and issue an improvement notice; repeated or wilful violations can support stronger action under the FSS Act. Avoid announcing a confirmed cause before toxin or quantitative results are available, and avoid relying on a single stool culture. Advise the hospital and family to report further cases, and check whether leftover food was distributed. The enforcement note should distinguish corrective actions from penal allegations.