INTRODUCTIONNon-typhoidal Salmonellae are important causes of bacterial food-borne infection, especially in institutional settings. An outbreak of gastrointestinal infection occurred in a military camp in January 2007, and an epidemiological outbreak investigation was conducted.

MATERIALS AND METHODSA survey was conducted on soldiers in the camp on their clinical symptoms, and recent meals consumed. After determining the affected meal, a subsequent survey was conducted on those who had eaten the meal. A case-control study was then performed to determine the outbreak's likely food source. Laboratory tests were also conducted to determine the bacteriological cause.

RESULTSOf the 94 responders, 55 (58.5%) met our case definition of gastrointestinal illness. The dinner on 9 January was the most likely affected meal, with the onset of symptoms occurring within 6 to 36 hours. The mashed potato was the most likely food source with an attack rate of 80.7% for those who consumed it versus 32.7% for those who did not (P <0.01). From the multivariate analysis, the mashed potato remained the only food item independently and significantly associated with infection, with a relative risk of infection 9.49 times those who did not consume it (95% CI, 2.73-32.97). Salmonella group E was cultured from 4 individuals. Although no specific contamination was identified, the mashed potato was stored for more than 5 hours before the last serving.

CONCLUSIONRisk during preparation of large quantities of food should be identified a priori, and measures taken to reduce them, to prevent outbreaks.

Case-Control Studies ; Disease Outbreaks ; Food Microbiology ; Gastroenteritis ; etiology ; Military Medicine ; Salmonella ; isolation & purification ; Salmonella Food Poisoning ; etiology ; Singapore ; Solanum tuberosum