Salmonella Outbreaks in Restaurants in Minnesota, 1995 Through 2003: Evaluation of the Role of Infected Foodworkers

J Food Prot. 2006 Aug;69(8):1870-8. doi: 10.4315/0362-028x-69.8.1870.

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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Consumer Product Safety
  • Disease Outbreaks
  • Electrophoresis, Gel, Pulsed-Field
  • Food Contamination / analysis*
  • Food Handling / methods*
  • Food Microbiology
  • Humans
  • Hygiene*
  • Minnesota / epidemiology
  • Restaurants*
  • Salmonella / classification
  • Salmonella / isolation & purification*
  • Salmonella Food Poisoning / epidemiology*
  • Serotyping
  • Time Factors