Genomic diversity and evolution within the species Streptococcus agalactiae.
Streptococcus agalactiae is a leading cause of invasive infections in neonates, and responsible for bovine mastitis. It is also a commensal bacterium adapted to asymptomatic colonization of the mammalian gut and of the genitourinary tract. Here, we report the analysis of a collection of 75 strains of human and animal origin by using serotyping, multilocus sequence typing, whole genome DNA-array hybridizations and sequence comparison of putatively virulence-associated loci. Although the most variable parts of the genome are the previously predicted genomic islands, significant genetic variations were present in the genome backbone. Evolution within genes encoding surface and secreted proteins and those involved in the biosynthesis of different capsular types is mainly due to recombination events leading to the replacement of a locus of several genes or to the allelic exchange of the internal part of a gene. These two processes, which led to a broad diversity of surface protein patterns, are probably involved in the diversity of interactions with the host and its immune system. According to gene content comparisons and phylogeny, recent gene replacements by horizontal gene transfer may occur but are rare events. Although specific gene patterns, with respect to the origin of the strains and the epidemiological characteristics, were not identified, we show that the recently described hypervirulent ST-17 lineage is a homogeneous group. The study highlights for the first time that this lineage contains a specific and conserved set of surface proteins, probably accounting for its high capacity to cause infections in newborns.
Brochet
Mathieu
M
Unité de Génomique des Microorganismes Pathogènes-URA CNRS 2171, Institut Pasteur, 25-28 rue du Docteur Roux, 75724 Paris Cedex 15, France.
Couvé
Elisabeth
E
Zouine
Mohamed
M
Vallaeys
Tatiana
T
Rusniok
Christophe
C
Lamy
Marie-Cécile
MC
Buchrieser
Carmen
C
Trieu-Cuot
Patrick
P
Kunst
Frank
F
Poyart
Claire
C
Glaser
Philippe
P
D000328:Adult; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D002415:Cats; D002417:Cattle; D002675:Child, Preschool; D004269:DNA, Bacterial / Q000032:analysis; D004285:Dogs; D019143:Evolution, Molecular; D005260:Female; D014644:Genetic Variation; D016680:Genome, Bacterial; D006168:Guinea Pigs; D006801:Humans; D007231:Infant, Newborn; D008565:Membrane Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D011817:Rabbits; D017422:Sequence Analysis, DNA; D012703:Serotyping; D013292:Streptococcus agalactiae / Q000145:classification* / Q000235:genetics* / Q000472:pathogenicity; D014774:Virulence / Q000235:genetics
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008565:Membrane Proteins