<i>Streptococcus</i>and<i>Lactobacillus</i>

Kilian, Mogens

doi:10.1002/9780470688618.taw0033

Cited by 13 publications

(14 citation statements)

References 525 publications

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“…Phylogenetic analysis based on 16S rRNA sequences of type strains of the more than 50 Streptococcus species reveal a clustering pattern that reflect their pathogenic potential and ecological preferences [1], [2]. One exception is the Mitis group, which contains one of the leading pathogens affecting mankind, Streptococcus pneumoniae , along with 11 species that are prototype commensals of the upper respiratory tract.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Streptococcus pneumoniae and Its Close Commensal Relatives

et al. 2008

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Streptococcus pneumoniae is a member of the Mitis group of streptococci which, according to 16S rRNA-sequence based phylogenetic reconstruction, includes 12 species. While other species of this group are considered prototypes of commensal bacteria, S. pneumoniae is among the most frequent microbial killers worldwide. Population genetic analysis of 118 strains, supported by demonstration of a distinct cell wall carbohydrate structure and competence pheromone sequence signature, shows that S. pneumoniae is one of several hundred evolutionary lineages forming a cluster separate from Streptococcus oralis and Streptococcus infantis. The remaining lineages of this distinct cluster are commensals previously collectively referred to as Streptococcus mitis and each represent separate species by traditional taxonomic standard. Virulence genes including the operon for capsule polysaccharide synthesis and genes encoding IgA1 protease, pneumolysin, and autolysin were randomly distributed among S. mitis lineages. Estimates of the evolutionary age of the lineages, the identical location of remnants of virulence genes in the genomes of commensal strains, the pattern of genome reductions, and the proportion of unique genes and their origin support the model that the entire cluster of S. pneumoniae, S. pseudopneumoniae, and S. mitis lineages evolved from pneumococcus-like bacteria presumably pathogenic to the common immediate ancestor of hominoids. During their adaptation to a commensal life style, most of the lineages gradually lost the majority of genes determining virulence and became genetically distinct due to sexual isolation in their respective hosts.

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Section: Introductionmentioning

confidence: 99%

Evolution of Streptococcus pneumoniae and Its Close Commensal Relatives

et al. 2008

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“…Isolates were cultured as described and species designation was confirmed by a combination of standard tests (40). …”

Section: Methodsmentioning

confidence: 99%

Emergence and Global Dissemination of Host-Specific Streptococcus agalactiae Clones

Sørensen

Poulsen

Ghezzo

et al. 2010

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To examine the global diversity of Streptococcus agalactiae (group B streptococci [GBS]) and to elucidate the evolutionary processes that determine its population genetics structure and the reported changes in host tropism and infection epidemiology, we examined a collection of 238 bovine and human isolates from nine countries on five continents. Phylogenetic analysis based on the sequences of 15 housekeeping genes combined with patterns of virulence-associated traits identified a genetically heterogeneous core population from which virulent lineages occasionally emerge as a result of recombination affecting major segments of the genome. Such lineages, like clonal complex 17 (CC17) and two distinct clusters of CC23, are exclusively adapted to either humans or cattle and successfully spread globally. The recent emergence and expansion of the human-associated and highly virulent sequence type 17 (ST17) could conceivably account, in part, for the increased prevalence of neonatal GBS infections after 1960. The composite structure of the S. agalactiae genome invalidates phylogenetic inferences exclusively based on multilocus sequence typing (MLST) data and thereby the previously reported conclusion that the human-associated CC17 emerged from the bovine-associated CC67.

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“…dysgalactiae was proposed for animal isolates. However, the names S. dysgalactiae and S. equisimilis are still used in clinical settings, and it has been argued that it would be practical to maintain the two taxa as separate species (29). According to the proposal of Vandamme and coworkers (52), S. dysgalactiae subsp.…”

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Delineation of Streptococcus dysgalactiae, Its Subspecies, and Its Clinical and Phylogenetic Relationship to Streptococcus pyogenes

Jensen

Kilian

2012

J Clin Microbiol

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The taxonomic status and structure of Streptococcus dysgalactiae have been the object of much confusion. Bacteria belonging to this species are usually referred to as Lancefield group C or group G streptococci in clinical settings in spite of the fact that these terms lack precision and prevent recognition of the exact clinical relevance of these bacteria. The purpose of this study was to develop an improved basis for delineation and identification of the individual species of the pyogenic group of streptococci in the clinical microbiology laboratory, with a special focus on S. dysgalactiae. We critically reexamined the genetic relationships of the species S. dysgalactiae, Streptococcus pyogenes, Streptococcus canis, and Streptococcus equi, which may share Lancefield group antigens, by phylogenetic reconstruction based on multilocus sequence analysis (MLSA) and 16S rRNA gene sequences and by emm typing combined with phenotypic characterization. Analysis of concatenated sequences of seven genes previously used for examination of viridans streptococci distinguished robust and coherent clusters. S. dysgalactiae consists of two separate clusters consistent with the two recognized subspecies dysgalactiae and equisimilis. Both taxa share alleles with S. pyogenes in several housekeeping genes, which invalidates identification based on single-locus sequencing. S. dysgalactiae, S. canis, and S. pyogenes constitute a closely related branch within the genus Streptococcus indicative of recent descent from a common ancestor, while S. equi is highly divergent from other species of the pyogenic group streptococci. The results provide an improved basis for identification of clinically important pyogenic group streptococci and explain the overlapping spectrum of infections caused by the species associated with humans.

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StreptococcusandLactobacillus

Cited by 13 publications

References 525 publications

Evolution of Streptococcus pneumoniae and Its Close Commensal Relatives

Evolution of Streptococcus pneumoniae and Its Close Commensal Relatives

Emergence and Global Dissemination of Host-Specific Streptococcus agalactiae Clones

Delineation of Streptococcus dysgalactiae, Its Subspecies, and Its Clinical and Phylogenetic Relationship to Streptococcus pyogenes

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