title: MLVA forSalmonella entericasubsp.entericaSerovar Dublin: Development of a Method Suitable for Inter-Laboratory Surveillance and Application in the Context of a Raw Milk Cheese Outbreak in France in 2012.
abstract: Salmonella entericasubspeciesenterica serovarDublin (S. Dublin) figures among the most frequently isolatedSalmonellastrains in humans in France. This serovar may affect production and animal health mainly in cattle herds with corresponding high economic losses. Given that the current gold standard method, pulsed-field gel electrophoresis (PFGE), provides insufficient discrimination for epidemiological investigations, we propose a standard operating procedure in this study for multiple-locus variable number tandem repeat analysis (MLVA) ofS.Dublin, suitable for inter-laboratory surveillance. Anin silicoanalysis on the genome ofS.Dublin strains CT_02021853 was performed to identify appropriate microsatellite regions. Of 21 VNTR loci screened, six were selected and 401 epidemiologically unrelated and related strains, isolated from humans, food and animals were analyzed to assess performance criteria such as typeability, discriminatory power and epidemiological concordance. The MLVA scheme developed was applied to an outbreak involvingSaint-Nectairecheese for which investigations were conducted in France in 2012, making it possible to discriminate between epidemiologically related strains and sporadic case strains, while PFGE assigned only a single profile. The six loci selected were sequenced on a large set of strains to determine the sequence of the repeated units and flanking regions, and their stability was evaluatedin vivothrough the analysis of the strains investigated from humans, food and the farm environment during the outbreak. The six VNTR selected were found to be stable and the discriminatory power of the MLVA method developed was calculated to be 0.954 compared with that for PFGE, which was only 0.625. Twenty-four reference strains were selected from the 401 examined strains in order to represent most of the allele diversity observed for each locus. This reference set can be used to harmonize MLVA results and allow data exchange between laboratories. This original MLVA protocol could be used easily and routinely for monitoring of serovar Dublin isolates and for conducting outbreak investigations.
authors.affiliation: Université PARIS-EST, Agence Nationale de Sécurité Sanitaire de l'Alimentation, de l'Environnement et du Travail, Laboratory for Food Safety Maisons-Alfort, France.
authors.forename: Marie-Léone
authors.initials: ML
authors.lastname: Vignaud
authors.affiliation: Université PARIS-EST, Agence Nationale de Sécurité Sanitaire de l'Alimentation, de l'Environnement et du Travail, Laboratory for Food Safety Maisons-Alfort, France.
authors.forename: Emeline
authors.initials: E
authors.lastname: Cherchame
authors.affiliation: Université PARIS-EST, Agence Nationale de Sécurité Sanitaire de l'Alimentation, de l'Environnement et du Travail, Laboratory for Food Safety Maisons-Alfort, France.
authors.forename: Muriel
authors.initials: M
authors.lastname: Marault
authors.affiliation: Université PARIS-EST, Agence Nationale de Sécurité Sanitaire de l'Alimentation, de l'Environnement et du Travail, Laboratory for Food Safety Maisons-Alfort, France.
authors.forename: Emilie
authors.initials: E
authors.lastname: Chaing
authors.affiliation: French National Reference Center for E. coli, Shigella and Salmonella, Institut Pasteur Paris, France.
authors.forename: Simon
authors.initials: S
authors.lastname: Le Hello
authors.affiliation: Department of Dairy Products, Center of Expertise for the Food Industry La Roche-sur-Foron, France.
authors.forename: Valerie
authors.initials: V
authors.lastname: Michel
authors.affiliation: French National Public Health Agency Saint-Maurice, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Jourdan-Da Silva
authors.affiliation: Université PARIS-EST, Agence Nationale de Sécurité Sanitaire de l'Alimentation, de l'Environnement et du Travail, Laboratory for Food Safety Maisons-Alfort, France.
authors.forename: Renaud
authors.initials: R
authors.lastname: Lailler
authors.affiliation: Université PARIS-EST, Agence Nationale de Sécurité Sanitaire de l'Alimentation, de l'Environnement et du Travail, Laboratory for Food Safety Maisons-Alfort, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Brisabois
authors.affiliation: Université PARIS-EST, Agence Nationale de Sécurité Sanitaire de l'Alimentation, de l'Environnement et du Travail, Laboratory for Food Safety Maisons-Alfort, France.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Cadel-Six
keywords: MLVA analysis; PFGE analysis; Salmonella Dublin; foodborne outbreak; protocol for inter-laboratory surveillance; raw milk cheese