title: Molecular identification in monophasic and nonmotile variants of Salmonella enterica serovar Typhimurium.
abstract: Variant strains of Salmonella enterica serovar Typhimurium, lacking one or both flagellar phases have been widely reported. The monophasic S.1,4,[5],12:i:- variant has emerged worldwide in the past few years and has become one of the most frequently encountered in many countries. In contrast, monophasic S.1,4,[5],12:-:1,2 and nonmotile S.1,4,[5],12:-:- strains are rarely described. This study investigated seven molecular markers to identify and delineate monophasic S.1,4,[5],12:i:- (n = 90), S.1,4,[5],12:-:1,2 (n = 25), nonmotile S.1,4,[5],12:-:- (n = 17) strains, and some serovar Typhimurium strains (n = 124) collected through the French Salmonella network between 2001 and 2010. Three markers were commonly detected in serovar Typhimurium and in all variant strains: STM2757, mdh and fliA-B. Monophasic S.1,4,[5],12:i:- were genotypically confirmed by the absence of the fljB, fljA, and hin genes. Nevertheless, 13 (14.5%) of them were positive for these last three genes, revealing monophasic strains named "inconsistent" as previously described. All nonmotile 1,4,[5],12:-:- strains had the fliC, fljA, fljB, and hin genes and the fliC gene was detected in 88% of monophasic S.1,4,[5],12:-:1,2 strains. The combination of the seven markers detection enables to recognize eight different genotypes within the S.1,4,[5],12:i:- collection, among which the Spanish and the U.S. clones previously described could be distinguished and assigned to a genotype. Based on this molecular approach, 71% of the French S.1,4,[5],12:i:- collection belonged to the Spanish clone, whereas only 2% were assigned to the U.S. clone. This study highlights the usefulness of these molecular markers and genotypes for identifying lineages, especially among the epidemiologically important monophasic S.1,4,[5],12:i:- variant.
authors.affiliation: French Agency for Food, Environmental and Occupational Health and Health (ANSES), Laboratory for Food Safety, 23 Avenue du Général de Gaulle, 94706, Maisons-Alfort, France.
authors.forename: M
authors.initials: M
authors.lastname: Bugarel
authors.forename: M-L
authors.initials: ML
authors.lastname: Vignaud
authors.forename: F
authors.initials: F
authors.lastname: Moury
authors.forename: P
authors.initials: P
authors.lastname: Fach
authors.forename: A
authors.initials: A
authors.lastname: Brisabois
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005602:France; D005819:Genetic Markers / Q000235:genetics; D014644:Genetic Variation; D016680:Genome, Bacterial; D016133:Polymerase Chain Reaction; D012486:Salmonella typhimurium / Q000145:classification / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D005819:Genetic Markers