Affiliation:
1. Department of Microbiology and Immunology, New York Medical College, Valhalla, New York 10595
Abstract
ABSTRACT
The FCT regions of
Streptococcus pyogenes
strains encode a variety of cell wall-anchored surface proteins that bind the extracellular matrix of the human host and/or give rise to pilus-like appendages. Strong linkage is evident between transcription-regulatory loci positioned within the FCT and
emm
regions and the
emm
pattern genotype marker for preferred infection of the throat or skin. These findings provide a basis for the hypothesis that FCT region gene products contribute to tissue-specific infection. In an initial series of steps to address this possibility, the FCT regions of 13 strains underwent comparative sequence analysis, the gene content of the FCT region was characterized for 113 strains via PCR, and genetic linkage was assessed. A history of extensive recombination within FCT regions was evident. The
emm
pattern D-defined skin specialist strains were highly homogenous in their FCT region gene contents, whereas the
emm
pattern A-C-defined throat specialist strains displayed a greater variety of forms. Most pattern A-C strains harbored
prtF1
(75%) but lacked
cpa
(75%). In contrast, the majority of
emm
pattern D strains had
cpa
(92%) but lacked
prtF1
(79%). Models based on FCT and
emm
region genotypes revealed the most parsimonious pathways of evolution. Using niche-determining candidate genes to infer phylogeny,
emm
pattern E strains—the so-called generalists, which lack a strong tissue site preference—occupied a transition zone separating most throat specialists from skin specialists. Overall, population genetic analysis supports the possibility that the FCT region gives rise to surface proteins that are largely necessary, but not always sufficient, to confer tissue site preference for infection.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
92 articles.
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