title: Salmonella Gallinarum field isolates from laying hens are related to the vaccine strain SG9R.
abstract: Salmonella enterica subspecies enterica serotype Gallinarum can cause severe systemic disease in chickens and a live Salmonella Gallinarum 9R vaccine (SG9R) has been used widely to control disease. Using whole-genome sequencing we found point mutations in the pyruvate dehydrogenase (aceE) and/or lipopolysaccharide 1,2-glucosyltransferase (rfaJ) genes that likely explain the attenuation of the SG9R vaccine strain. Molecular typing using Pulsed Field Gel Electrophoresis and Multiple-Locus Variable number of tandem repeat Analysis showed that strains isolated from different layer flocks in multiple countries and the SG9R vaccine strain were similar. The genome of one Salmonella Gallinarum field strain, isolated from a flock with a mortality peak and selected on the basis of identical PFGE and MLVA patterns with SG9R, was sequenced. We found 9 non-silent single-nucleotide differences distinguishing the field strain from the SG9R vaccine strain. Our data show that a Salmonella Gallinarum field strain isolated from laying hens is almost identical to the SG9R vaccine. Mutations in the aceE and rfaJ genes could explain the reversion to a more virulent phenotype. Our results highlight the importance of using well defined gene deletion mutants as vaccines.
authors.affiliation: Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium. Electronic address: filip.vanimmerseel@ugent.be.
authors.forename: F
authors.initials: F
authors.lastname: Van Immerseel
authors.forename: D J
authors.initials: DJ
authors.lastname: Studholme
authors.forename: V
authors.initials: V
authors.lastname: Eeckhaut
authors.forename: M
authors.initials: M
authors.lastname: Heyndrickx
authors.forename: J
authors.initials: J
authors.lastname: Dewulf
authors.forename: I
authors.initials: I
authors.lastname: Dewaele
authors.forename: S
authors.initials: S
authors.lastname: Van Hoorebeke
authors.forename: F
authors.initials: F
authors.lastname: Haesebrouck
authors.forename: H
authors.initials: H
authors.lastname: Van Meirhaeghe
authors.forename: R
authors.initials: R
authors.lastname: Ducatelle
authors.forename: K
authors.initials: K
authors.lastname: Paszkiewicz
authors.forename: R W
authors.initials: RW
authors.lastname: Titball
mesh_terms: D000818:Animals; D002645:Chickens; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D005838:Genotype; D018598:Minisatellite Repeats; D058889:Molecular Typing; D009154:Mutation; D020641:Polymorphism, Single Nucleotide; D011201:Poultry Diseases / Q000382:microbiology*; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D022562:Salmonella Vaccines; D019779:Salmonella enterica / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D022562:Salmonella Vaccines
keywords: Reversion; Salmonella Gallinarum; Vaccine; Whole genome sequencing