A case-control study investigating an outbreak of Bacillus cereus food poisoning in a hotel in Malta

Abstract

Bacillus cereus food poisoning is an intoxication with a short incubation period, characterised predominantly by sudden onset of nausea and vomiting in some cases and in others by abdominal colic, severe watery diarrhoea and tenesmus. The illness generally persists no longer than 24 hours and is rarely fatal. In February 1996 the Department of Public Health investigated an outbreak of food poisoning involving at least 92 persons among local and foreign guests at a local hotel. B. cereus was implicated as a cause of the outbreak. A case-control study was performed on 61 cases and 80 controls from among hotel residents using a detailed questionnaire. Consumption of rice at a hotel lunch was associated with subsequent development of symptoms (OR = 2.97, 95% CI 1.34 - 6.77). The food-specific attack rate for rice was 0.53 (P = 0.0034). B. cereus (7.5 x 103 organisms /g) was isolated from leftover samples of boiled rice and from the stools of three patients.