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A regional outbreak of S. Typhimurium in Denmark and identification of the source using MLVA typing

M Torpdahl1, G Sorensen, S Ethelberg

  • 1Statens Serum Institut, Department of Bacteriology, Mycology and Parasitology, Copenhagen, Denmark.

Euro Surveillance : Bulletin Europeen Sur Les Maladies Transmissibles = European Communicable Disease Bulletin
|June 8, 2006
PubMed

Insights

Multiple Locus Variable Number of Tandem Repeats analysis (MLVA) identified a Salmonella Typhimurium outbreak in Denmark. MLVA traced the human infections to a specific pig herd, demonstrating its value in surveillance and outbreak investigations.

Area of Science:

  • Foodborne illness surveillance
  • Microbial typing techniques
  • Public health microbiology

Background:

  • Salmonella Typhimurium surveillance in Denmark relies on phage typing, antibiogram typing, and pulsed-field gel electrophoresis (PFGE).
  • PFGE has limitations in discriminating between certain phage types and distinguishing related from unrelated isolates.
  • Multiple Locus Variable Number of Tandem Repeats analysis (MLVA) was implemented for enhanced S. Typhimurium surveillance since 2004.

Purpose of the Study:

  • To evaluate the effectiveness of MLVA in identifying and tracing outbreaks of Salmonella Typhimurium.
  • To compare the discriminatory power of MLVA with PFGE in distinguishing S. Typhimurium isolates.
  • To identify the source of a 2005 S. Typhimurium outbreak in Denmark.

Main Methods:

  • Application of MLVA for routine surveillance typing of S. Typhimurium isolates.
  • Comparative analysis of MLVA and PFGE profiles for human, animal, and food isolates.
  • Epidemiological data collection to support source attribution.

Main Results:

  • MLVA identified a 2005 outbreak involving 26 cases of S. Typhimurium infection.
  • Human outbreak isolates shared identical PFGE and MLVA types with an isolate from a local pig herd and its slaughterhouse.
  • Other S. Typhimurium DT12 isolates with the same PFGE profile exhibited distinct MLVA types, highlighting MLVA's superior discriminatory ability.

Conclusions:

  • MLVA significantly enhanced the ability to detect and investigate S. Typhimurium outbreaks.
  • The study successfully traced the source of the outbreak to a specific pig herd.
  • MLVA is a valuable tool for both routine surveillance and outbreak investigations of S. Typhimurium.

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