Salmonella Outbreaks in Restaurants in Minnesota, 1995 through 2003: Evaluation of the Role of Infected Foodworkers
Abstract:The 23 restaurant-associated salmonellosis outbreaks that occurred in Minnesota from 1995 through 2003 were reviewed to characterize the role of infected foodworkers. The median duration of the outbreaks was 21 days (range, 1 to 517 days). The median number of culture-confirmed patron cases per outbreak was seven (range, 1 to 36 cases). The median incubation for patron cases ranged from 9 h to 5.9 days. A specific food vehicle was implicated in four outbreaks and suspected in five. Salmonella of the same serotype and pulsed-field gel electrophoresis subtype as that found in patrons was recovered from foodworkers in 19 outbreaks. Overall, 12% (129 of 1,033) of foodworkers tested positive for Salmonella. Sixty-four (53%) of 121 Salmonella-positive foodworkers reported not having had a recent gastrointestinal illness. Overall, the median duration of Salmonella shedding was 16 days. Among foodworkers who reported gastrointestinal illness, the median shedding duration was 30 days as compared with 3 days for asymptomatic foodworkers. Positive environmental samples were recovered in 4 (33%) of 12 outbreaks. No specific food vehicle was identified in any outbreaks associated with Salmonella-positive environmental samples. The median duration of outbreaks with positive environmental samples (187 days) was significantly longer than the median duration of outbreaks with negative environmental results (26 days, P = 0.03). A higher proportion of Salmonella-positive foodworkers (22 versus 8%) was identified in outbreaks with positive environmental samples. Salmonella outbreaks in restaurants are frequently prolonged yet produce a small number of confirmed patron cases. Prolonged outbreak durations suggest a persistent reservoir of contamination. Infected foodworkers likely serve as an important source for Salmonella transmission. Therefore, assessment of foodworker infection is essential for controlling restaurant outbreaks.
Document Type: Research Article
Affiliations: 1: Acute Disease Investigation and Control Section, Minnesota Department of Health, P.O. Box 64975, St. Paul, Minnesota 55164-0975, USA; Division of Environmental Health Sciences, School of Public Health, University of Minnesota, 1260 Mayo (MMC 807), 420 Delaware Street S.E., Minneapolis, Minnesota 55455, USA 2: Acute Disease Investigation and Control Section, Minnesota Department of Health, P.O. Box 64975, St. Paul, Minnesota 55164-0975, USA 3: Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, 136F Andrew Boss, 1354 Eckles Avenue, St. Paul, Minnesota 55108, USA 4: Public Health Laboratory, Minnesota Department of Health, P.O. Box 64899, St. Paul, Minnesota 55164-0899, USA 5: Division of Environmental Health Sciences, School of Public Health, University of Minnesota, 1260 Mayo (MMC 807), 420 Delaware Street S.E., Minneapolis, Minnesota 55455, USA
Publication date: August 1, 2006
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