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Infect. Immun., 03 1995, 994-1003, Vol 63, No. 3
JM Musser, V Kapur, J Szeto, X Pan, DS Swanson and DR Martin
Chromosomal diversity and relationships among 126 Streptococcus pyogenes
strains expressing M1 protein from 13 countries on five continents were
analyzed by multilocus enzyme electrophoresis and restriction fragment
profiling by pulsed-field gel electrophoresis. All isolates were studied
for the presence of the gene encoding streptococcal pyrogenic exotoxin A by
PCR. Strain subsets were also examined by automated DNA sequencing for
allelic polymorphism in genes encoding M protein (emm), streptococcal
pyrogenic exotoxin A (speA), streptokinase (ska), pyrogenic exotoxin B
(interleukin-1 beta convertase) (speB), and C5a peptidase (scp). Seven
distinct emm1 alleles that encode M proteins differing at one or more amino
acids in the N-terminal variable region were identified. Although
substantial levels of genetic diversity exist among M1-expressing
organisms, most invasive disease episodes are caused by two subclones
marked by distinctive multilocus enzyme electrophoretic profiles and
pulsed-field gel electrophoresis restriction fragment length polymorphism
(RFLP) types. One of these subclones (ET 1/RFLP pattern 1a) has the speA
gene and was recovered worldwide. Identity of speA, emm1, speB, and ska
alleles in virtually all isolates of ET 1/RFLP type 1a means that these
organisms share a common ancestor and that global dispersion of this M1-
expressing subclone has occurred very recently. The occurrence of the same
emm and ska alleles in strains that are well differentiated in overall
chromosomal character demonstrates that horizontal transfer and
recombination play a fundamental role in diversifying natural populations
of S. pyogenes.
Copyright © 1995, American Society for Microbiology
Genetic diversity and relationships among Streptococcus pyogenes strains expressing serotype M1 protein: recent intercontinental spread of a subclone causing episodes of invasive disease
Department of Pathology, Baylor College of Medicine, Houston, Texas 77030.
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