Abstract
BackgroundDuring August 2006, a protracted outbreak of Salmonella (S.) Enteritidis infections in a large Hamburg nursing home was investigated.MethodsA site visit of the home was conducted and food suppliers' premises tested for Salmonella. Among nursing home residents a cohort study was carried out focusing on foods consumed in the three days before the first part of the outbreak. Instead of relying on residents' memory, data from the home's patient food ordering system was used as exposure data. S. Enteritidis isolates from patients and suspected food vehicles were phage typed and compared.ResultsWithin a population of 822 nursing home residents, 94 case patients among residents (1 fatality) and 17 among staff members were counted 6 through 29 August. The outbreak peaked 7 through 9 August, two days after a spell of very warm summer weather. S. Enteritidis was consistently recovered from patients' stools throughout the outbreak. Among the food items served during 5 through 7 August, the cohort study pointed to afternoon cake on all three days as potential risk factors for disease. Investigation of the bakery supplying the cake yielded S. Enteritidis from cakes sampled 31 August. Comparison of the isolates by phage typing demonstrated both isolates from patients and the cake to be the exceedingly rare phage type 21c.ConclusionCake (various types served on various days) contaminated with S. Enteritidis were the likely vehicle of the outbreak in the nursing home. While the cakes were probably contaminated with low pathogen dose throughout the outbreak period, high ambient summer temperatures and failure to keep the cake refrigerated led to high pathogen dose in cake on some days and in some of the housing units. This would explain the initial peak of cases, but also the drawn out nature of the outbreak with cases until the end of August. Suggestions are made to nursing homes, aiding in outbreak prevention. Early outbreak detection is crucial, such that counter measures can be swift and drawn-out outbreaks of nosocomial food-borne infections avoided.
Highlights
During August 2006, a protracted outbreak of Salmonella (S.) Enteritidis infections in a large Hamburg nursing home was investigated
In early August 2006 a large senior care facility in Hamburg reported a nosocomial outbreak of gastroenteritis to the local health department
Enteritidis isolates from the outbreak were submitted to phage typing and compared to other isolates currently circulating in Germany by the National Reference Centre for Salmonellae (NRC)
Summary
During August 2006, a protracted outbreak of Salmonella (S.) Enteritidis infections in a large Hamburg nursing home was investigated. In early August 2006 a large senior care facility in Hamburg reported a nosocomial outbreak of gastroenteritis to the local health department. Residents were falling ill with symptoms of diarrhoea and vomiting and the outbreak was continuing well beyond one week. Stool samples from early cases yielded Salmonella enterica ssp.enterica serotype Enteridis This is the Salmonella serotype most frequently reported in Germany (30,000–50,000 cases per year), especially in later summer. Enteritidis infections [1,2]. On 19 August a formal investigation into the protracted outbreak was launched, aiming to identify and contain the apparently continuous source of infection
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