Salmonella outbreaks in restaurants in Minnesota, 1995 through 2003: evaluation of the role of infected foodworkers.
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.
Medus
Carlota
C
Acute Disease Investigation and Control Section, Minnesota Department of Health, P.O. Box 64975, St. Paul, Minnesota 55164-0975, USA. carlota.medus@health.state.mn.us
Smith
Kirk E
KE
Bender
Jeffrey B
JB
Besser
John M
JM
Hedberg
Craig W
CW
D003257:Consumer Product Safety; D004196:Disease Outbreaks; D016521:Electrophoresis, Gel, Pulsed-Field; D005506:Food Contamination / Q000032:analysis*; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D006801:Humans; D006920:Hygiene; D008910:Minnesota / Q000453:epidemiology; D012147:Restaurants; D012475:Salmonella / Q000145:classification / Q000302:isolation & purification*; D012478:Salmonella Food Poisoning / Q000453:epidemiology*; D012703:Serotyping; D013997:Time Factors