title: Multiple-locus variable-number tandem repeat analysis of Salmonella enterica subsp. enterica serovar Dublin.
abstract: OBJECTIVE
  Salmonella serovar Dublin causes disease in cattle and leads to considerable production losses. In humans, severe invasive disease and high mortality rates are reported. The presently available typing methods provide insufficient discrimination within Salm. Dublin for epidemiological investigations. In this study, we developed a multiple-locus variable-number tandem repeat analysis (MLVA) scheme for high discriminatory typing of Salm. Dublin.
  
  
  RESULTS
  Nine loci of variable number of tandem repeats (VNTRs) were evaluated based on a panel of 40 diverse isolates. The four most discriminative VNTRs were selected for further MLVA analysis. The discriminatory power was evaluated on 272 veterinary and human isolates plus 29 outbreak-related isolates. MLVA divided the 272 isolates into 103 types and successfully identified isolates from an epidemiologically confirmed outbreak. VNTRs exhibited 100% in vitro stability and contained only true repeats. The discriminatory power of the MLVA was compared to pulsed-field gel electrophoresis (PFGE). When analysing a subset of 106 isolates, MLVA obtained 60 types (index of diversity (DI) of 0·97), while PFGE revealed 10 types (DI of 0·57).
  
  
  CONCLUSIONS
  The technique showed a significantly enhanced discriminatory power compared with the current 'gold standard' PFGE. MLVA is a fast and low-cost method.
  
  
  CONCLUSIONS
  This MLVA method can be recommended to be used in routine subtyping of isolates for outbreak investigations and disease surveillance. The method may provide valuable additional information that can improve the effectiveness of epidemiological investigations of Salm. Dublin infections in patients as well as in the primary production and thereby contribute to the efforts of reducing transmission of infection.
authors: Department of Microbiology and Infection Control, Foodborne Pathogens, Statens Serum Institut, Copenhagen, Denmark; National Food Institute, Technical University of Denmark, Mørkhøj, Denmark.
authors: M K
authors: MK
authors: Kjeldsen
authors: M
authors: M
authors: Torpdahl
authors: J
authors: J
authors: Campos
authors: K
authors: K
authors: Pedersen
authors: E M
authors: EM
authors: Nielsen
mesh_terms: D000818:Animals; D015373:Bacterial Typing Techniques / Q000379:methods*; D002417:Cattle; D004196:Disease Outbreaks; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D018598:Minisatellite Repeats; D058885:Multilocus Sequence Typing / Q000379:methods*; D012480:Salmonella Infections / Q000453:epidemiology / Q000382:microbiology; D019779:Salmonella enterica / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification
keywords: Salmonella; genotyping; molecular epidemiology