title: MLST scheme of Ehrlichia ruminantium: genomic stasis and recombination in strains from Burkina-Faso.
abstract: Heartwater, caused by the intracellular bacterium Ehrlichia ruminantium, is a major tick-borne disease of livestock in Africa also introduced in the Caribbean. The main problem encountered with the control of this disease is the lack of efficient vaccine in the field. This is thought to be related to the high genetic diversity of strains circulating in a same area. A set of eight circulating strains was isolated from a herd of cows in a small locality in Burkina-Faso and analyzed along with two reference strains, i.e. ERGA and ERWO, for which full-length genome was available. A MLST analysis was developed based on the genes gltA, groEL, lepA, lipA, lipB, secY, sodB and sucA. Phylogeny analysis was conducted both on concatenated MLST loci and on each individual locus. This showed differing phylogenies for each individual target gene. Most of the recorded polymorphism was borne by three strains: 331, 469 and 623. The neutrality hypothesis could not be rejected. Recombination and linkage disequilibrium were shown to have occurred. A core of seven strains displayed little polymorphism and signs of most likely ancient recombination events. The two reference strains, one from the Caribbean separated from west African strains three centuries ago and another one isolated in South Africa, were very closely related to the core strains whereas the three differing strains displayed recombination and most of the parcimony informative sites. These data suggest that some strains are in genomic stasis, as expected for intracellular parasites, while others emerge in the same area with DNA polymorphism. This work also shows that the MLST scheme developed can discriminate between these two kinds of strains.
authors.affiliation: CIRDES Laboratoire de Biotechnologie (URBIO), Bobo-Dioulasso, Burkina-Faso.
authors.forename: Hassane
authors.initials: H
authors.lastname: Adakal
authors.forename: Damien F
authors.initials: DF
authors.lastname: Meyer
authors.forename: Catherine
authors.initials: C
authors.lastname: Carasco-Lacombe
authors.forename: Valérie
authors.initials: V
authors.lastname: Pinarello
authors.forename: Florian
authors.initials: F
authors.lastname: Allègre
authors.forename: Karine
authors.initials: K
authors.lastname: Huber
authors.forename: Frederic
authors.initials: F
authors.lastname: Stachurski
authors.forename: Serge
authors.initials: S
authors.lastname: Morand
authors.forename: Dominique
authors.initials: D
authors.lastname: Martinez
authors.forename: Thierrry
authors.initials: T
authors.lastname: Lefrançois
authors.forename: Nathalie
authors.initials: N
authors.lastname: Vachiery
authors.forename: Roger
authors.initials: R
authors.lastname: Frutos
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics; D002050:Burkina Faso / Q000453:epidemiology; D017691:Caribbean Region; D002417:Cattle; D018834:Chaperonin 60 / Q000032:analysis / Q000235:genetics; D016995:Ehrlichia ruminantium / Q000235:genetics*; D019143:Evolution, Molecular; D005798:Genes, Bacterial; D006357:Heartwater Disease / Q000453:epidemiology / Q000382:microbiology*; D006706:Homeostasis / Q000235:genetics*; D026863:Ixodidae / Q000382:microbiology; D015810:Linkage Disequilibrium; D010802:Phylogeny; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA / Q000379:methods*; D013045:Species Specificity; D013482:Superoxide Dismutase / Q000032:analysis / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D018834:Chaperonin 60; C088618:lipase activator protein, Bacteria; C087504:SodB protein, Bacteria; D013482:Superoxide Dismutase