Salmonella Typhimurium outbreak associated with smoked pork tenderloin in Denmark, January to March 2011

Abstract

Background: An outbreak of salmonellosis (Salmonella Typhimurium, phage type DT120) occurred from 26 January to 15 March 2011, in Denmark, with 22 laboratory confirmed cases. Hypothesis-generating patient interviews gave rise to the suspicion that smoked pork tenderloin was the source of infection. The primary objective of this study was to identify the source of the outbreak in order to initiate appropriate control measures. Methods: A matched (1:2) case–control study was conducted. A case was defined as a person residing in Denmark whose stool sample tested positive for S. Typhimurium, with a particular multilocus variable-number tandem repeat profile, from January to March 2011. Controls were matched to cases on age, gender, and municipality of residence. Results: Of 21 interviewed cases, 19 (91%) indicated that they typically ate smoked pork tenderloin more than once a week, compared with 13 (33%) of 39 interviewed controls (matched odds ratio 19.6, 95% confidence interval 2.6–153). Eighteen (86%) cases indicated that they might have consumed smoked pork tenderloin the week before becoming ill, compared with 1 (4%) control who had eaten the product a week before the interview. Two cases provided the brand name of the product and the supermarket where it was purchased. Conclusions: The results show a strong statistically significant association between the consumption of smoked pork tenderloin and S. Typhimurium infection. The European Rapid Alert System for Food and Feed was used to notify these findings to the competent authorities in the country of origin of the product. Subsequently, the smoked pork tenderloin of the brand in question, dating from 1 January to 1 May 2011, was recalled from consumers.

Keywords::

• Salmonella Typhimurium
• case–control study
• foodborne outbreak
• Denmark
• pork

Acknowledgements

The authors would like to thank the medical microbiology laboratories for submitting samples to SSI for typing, Gitte Sørensen at the Danish Technical University (DTU Food) for performing the phage typing, and Mia Torpdahl for providing additional MLVA information. The authors would also like to acknowledge the work of the Central Outbreak Management Group (COMG), as well as the interview team, Dominik Wessely, Henriette Juel Larsen, Louise Hansen, and Martin Vestergaard, in this investigation. The authors thank Marion Muehlen, EPIET coordinator, and Kåre Mølbak, Head of the Epidemiology Department at SSI, for their suggestions and contributions to the manuscript.

Declaration of interest: None declared. This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.