OUTBREAK OF SHIGELLA-FLEXNERI LINKED TO SALAD PREPARED AT A CENTRAL COMMISSARY IN MICHIGAN

IN AUGUST 1992, the Michigan Department of Public Health was notified of a cluster of persons with Shigella flexneri infections, all of whom had eaten at different outlets of a single restaurant chain. The chai n prepared many foods at a central kitchen. A matched case-control stu dy to determine risk factors for illness among patrons of the restaura nt chain was undertaken. An inspection of the commissary and a review of commissary inspection and employee records were conducted. Of the 4 6 patients identified, 44 had eaten tossed salad versus 33 of the 71 c ontrols (matched odds ratio = 56.9; 95 percent confidence interval 5.0 , 648.1). Improper salad preparation techniques were used, and the sal ad preparation area had not been inspected in several years. Some sala d preparers had been ill shortly before the outbreak but continued to work. The greater use of central kitchens could lead to larger outbrea ks of illness related to improper food handling. Raw vegetables are a potential vehicle for transmission of shigellosis. Coordination of all agencies responsible for inspecting commissaries should be assured. A ssuring restriction of ill food handlers will require management to ta ke an active role in identification of ill employees and in the develo pment of incentives to report illness.