Wedding Jollof Rice Held Overnight at Ambient Temperature
At a wedding reception in Ibadan, a caterer cooks 60 kg of jollof rice and 40 kg of chicken stew between 2 p.m. and 6 p.m. on Friday. The food is served at 8 p.m., but about 25 kg of rice and 12 kg of stew remain. The caterer covers the pots and leaves them on a wooden table in an unventilated store room. At 8 a.m. on Saturday the pots are reheated on high heat for about 15 minutes, then served at a family gathering at 10 a.m. By 2 p.m., six of the 30 people who ate the reheated rice have vomited; two also have abdominal cramps. None has fever or diarrhoea. A food handler who prepared the rice had a small uncovered cut on his thumb. The caterer says the food smelled fine and was properly heated, so it could not have caused illness. Inspectors find the store room at 31°C and the rice pot at 42°C at 9 a.m.
1. Which hazard category and which two organisms best fit the evidence? Explain how the incubation period and symptoms point toward or away from each.
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Step 1: classify. These are biological hazards - bacteria or their toxins - not chemical or physical. The vomiting-only picture with no fever points to a preformed toxin rather than an invasive infection.
Step 2: match the timing. Vomiting began within about 4 hours of the 10 a.m. meal (by 2 p.m.). That short incubation fits Bacillus cereus emetic toxin (1–6 h) and Staphylococcus aureus toxin (2–6 h). It does not fit Clostridium perfringens (usually 8–16 h, diarrhoea dominant) or typhoid (fever, 1–3 weeks).
Step 3: weigh the evidence. Cooked rice held at 31°C for 14 hours is the classic route for B. cereus: spores survive cooking, germinate in warm rice, and produce a heat-stable toxin. The uncovered thumb cut makes S. aureus plausible, because a handler can transfer it to rice during serving. Neither can be excluded from symptoms alone; both should be investigated. The heat-stable toxins are not destroyed by the 15-minute reheat, which explains why reheated food still caused illness.
2. The caterer argues that reheating makes the food safe. Evaluate that argument and state the immediate corrective actions for the remaining food and service.
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Reheating is not a cure. High heat kills vegetative bacteria, but the toxins of B. cereus and S. aureus are heat-stable; the rice may also be heated unevenly in a large pot. The argument therefore fails on both microbiology and practice.
Immediate actions: (1) stop serving the remaining rice and stew and place them on hold, labelled; (2) discard them if they cannot be kept safely - they have already been implicated and held in the danger zone; (3) take the names of ill guests and advise them to seek care, especially if vomiting persists; (4) notify the local government environmental health officer and the state ministry of health; (5) exclude the handler with the uncovered thumb cut from food handling until the lesion is covered and healed; (6) clean and sanitise pots, tables and the store room; (7) keep samples or records that help the investigation. Do not simply reheat and serve again.
3. What specific control would have prevented this outbreak at each step: cooking, holding, cooling, and reheating?
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Controls by step:
- Cooking: cook rice in batches small enough to reach safe temperature; do not leave large pots to cool slowly.
- Holding: if serving is delayed, hold hot food at 60°C or above; use a probe thermometer, not guesswork. The 42°C pot was in the danger zone.
- Cooling: if food must be cooled, divide it into shallow pans, use an ice bath or cold room, and get it from 60°C to 5°C within a short, monitored period (a common target is 2 hours to 21°C and a further 4 hours to 5°C).
- Reheating: reheat to at least 74°C throughout, measured at the centre, and hold at 60°C; discard food that has spent more than 2 hours in the 5–60°C zone.
- Handler: cover cuts with a waterproof dressing and glove, or move the handler away from ready-to-eat food.
The key is time-temperature control, not smell or taste.