Sequence type 1 group B Streptococcus, an emerging cause of invasive disease in adults, evolves by small genetic changes.
Proc Natl Acad Sci U S A
; 112(20): 6431-6, 2015 May 19.
Article
em En
| MEDLINE
| ID: mdl-25941374
ABSTRACT
The molecular mechanisms underlying pathogen emergence in humans is a critical but poorly understood area of microbiologic investigation. Serotype V group B Streptococcus (GBS) was first isolated from humans in 1975, and rates of invasive serotype V GBS disease significantly increased starting in the early 1990s. We found that 210 of 229 serotype V GBS strains (92%) isolated from the bloodstream of nonpregnant adults in the United States and Canada between 1992 and 2013 were multilocus sequence type (ST) 1. Elucidation of the complete genome of a 1992 ST-1 strain revealed that this strain had the highest homology with a GBS strain causing cow mastitis and that the 1992 ST-1 strain differed from serotype V strains isolated in the late 1970s by acquisition of cell surface proteins and antimicrobial resistance determinants. Whole-genome comparison of 202 invasive ST-1 strains detected significant recombination in only eight strains. The remaining 194 strains differed by an average of 97 SNPs. Phylogenetic analysis revealed a temporally dependent mode of genetic diversification consistent with the emergence in the 1990s of ST-1 GBS as major agents of human disease. Thirty-one loci were identified as being under positive selective pressure, and mutations at loci encoding polysaccharide capsule production proteins, regulators of pilus expression, and two-component gene regulatory systems were shown to affect the bacterial phenotype. These data reveal that phenotypic diversity among ST-1 GBS is mainly driven by small genetic changes rather than extensive recombination, thereby extending knowledge into how pathogens adapt to humans.
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Texto completo:
1
Bases de dados:
MEDLINE
Assunto principal:
Streptococcus agalactiae
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Adaptação Biológica
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Doenças Transmissíveis Emergentes
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Evolução Biológica
Limite:
Adult
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Humans
País/Região como assunto:
America do norte
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Ano de publicação:
2015
Tipo de documento:
Article