Davis H, Taylor J P, Perdue J N, Stelma G N, Humphreys J M, Rowntree R, Greene K D
Division of Field Services, Centers for Disease Control, Atlanta, GA 30333.
Am J Epidemiol. 1988 Dec;128(6):1312-21. doi: 10.1093/oxfordjournals.aje.a115084.
In the period August 30-October 7, 1986, 347 persons in adjacent west Texas counties (Ector and Midland) contracted culture-confirmed Shigella sonnei gastroenteritis. A case-control study showed an increased risk of acquiring shigellosis in Ector County with eating at outlets of fast-food Restaurant A, and in Midland County with eating at Restaurant B or C. A second case-control study, of persons who had eaten at Ector County outlets of Restaurant A, showed an increased risk of acquiring shigellosis with eating foods containing shredded lettuce and tomatoes, which were served together (odds ratio = 68.8; 95% confidence interval 8.5-293.1). All implicated restaurants received shredded lettuce produced at one lettuce-shredding plant; two implicated restaurants did not receive tomatoes from the lot delivered to other implicated restaurants. The lettuce-shredding plant distributed shredded lettuce and intact lettuce; restaurants that received only intact lettuce were not involved in the outbreak. Investigation at the lettuce-shredding plant suggested that a food handler might have been the source of contamination and that the method of processing might have allowed cross-contamination to occur. In the laboratory, the outbreak strain of S. sonnei multiplied rapidly on shredded lettuce at 22 C and survived on refrigerated shredded lettuce for at least seven days. This outbreak, one of the largest outbreaks of Shigella infections in the United States in the last decade, indicates that a large, geographically widespread shigellosis outbreak can result from contaminated shredded lettuce that is distributed commercially.
1986年8月30日至10月7日期间，得克萨斯州西部相邻的两个县（埃克特县和米德兰县）有347人感染了经培养确诊的宋内志贺菌性肠胃炎。一项病例对照研究显示，在埃克特县，在快餐餐厅A的门店就餐会增加感染志贺菌病的风险；在米德兰县，在餐厅B或C就餐会增加感染风险。第二项针对在埃克特县餐厅A门店就餐人员的病例对照研究表明，食用含有一起供应的生菜丝和西红柿的食物会增加感染志贺菌病的风险（比值比=68.8；95%置信区间8.5 - 293.1）。所有受牵连的餐厅都收到了一家生菜切丝厂生产的生菜丝；两家受牵连的餐厅没有收到供应给其他受牵连餐厅的那批西红柿。生菜切丝厂既分发生菜丝也分发完整的生菜；只收到完整生菜的餐厅未卷入此次疫情。对生菜切丝厂的调查表明，一名食品处理人员可能是污染源，而且加工方法可能导致了交叉污染。在实验室中，宋内志贺菌的疫情菌株在22℃的生菜丝上迅速繁殖，并且在冷藏的生菜丝上存活了至少七天。此次疫情是美国过去十年中最大的志贺菌感染疫情之一，表明商业分发的受污染生菜丝可导致大规模、地域广泛的志贺菌病疫情。
