Een Salmonella-typhimurium-epidemie in verband gebracht met ambachtelijk gezouten, gerookte en gedroogde varkensham

To discover the cause of an outbreak of gastroenteritis after a family party.

Design

Retrospective cohort study.

Methods

All 109 party-goers were asked to complete a written questionnaire about consumed food products and demografic and clinical variables and to hand in a faeces sample. The data were collected at the Public Health Institute Midden-Limburg, the Netherlands. Faeces and the remaining food products were examined microbiologically. The attack rates and the incidence rates of positive faeces culture among consumers and non-consumers of specific food products were calculated as well as the corresponding relative risks (RR) with 95 confidence intervals (95 CI).

Results

The overall attack rate was 35. Salmonella typhimurium phage type 20 was found in ‘Coburger ham’ and statistically significantly more frequently in faeces of ill compared with non-ill party-goers (RR: 6.4; 95 CI: 2.5-16.1). Twenty-eight different food products were served. Consumption of ‘Coburger ham’ only, was statistically significantly related to a positive faeces culture (RR: 4.1; 95 CI: 2.0-8.5). Only consumption of ‘Coburger ham’ and of ‘bone ham’ was statistically significantly related to being ill (RR: 2.4; 95 CI: 1.5-4.0 and RR: 1.4; 95 CI: 1.1-1.9, respectively). ‘Coburger ham’ and ‘bone ham’ originated from the same batch of raw meat and were prepared in the same manner in the same salt bath. The shorter duration of salting and drying of ‘Coburger ham’ compared with ‘bone ham’ corresponded with a higher relative risk of becoming ill.

Conclusion

Consumption of ‘bone ham’ and ‘Coburger ham’ infected with S. typhimurium phage type 20 caused the outbreak. Traditional salting, drying and smoking of raw pork meat was not antimicrobiologically effective against S. typhimurium. Investigation of the antimicrobiological effect of the tradional preparation of meat and the importance of Good Manufacturing Practices and quality control in all stages of production of pork meat, according to the principles of Hazard Analysis and Critical Control Points, is advised.