title: Genetic diversity and relationships among Streptococcus pyogenes strains expressing serotype M1 protein: recent intercontinental spread of a subclone causing episodes of invasive disease.
abstract: 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.
authors.affiliation: Department of Pathology, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: J M
authors.initials: JM
authors.lastname: Musser
authors.forename: V
authors.initials: V
authors.lastname: Kapur
authors.forename: J
authors.initials: J
authors.lastname: Szeto
authors.forename: X
authors.initials: X
authors.lastname: Pan
authors.forename: D S
authors.initials: DS
authors.lastname: Swanson
authors.forename: D R
authors.initials: DR
authors.lastname: Martin
mesh_terms: D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002352:Carrier Proteins; D020170:Caspase 1; D003546:Cysteine Endopeptidases / Q000235:genetics; D004196:Disease Outbreaks; D005098:Exotoxins / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D014943:Global Health; D006801:Humans; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D012150:Polymorphism, Restriction Fragment Length; D017386:Sequence Homology, Amino Acid; D013290:Streptococcal Infections / Q000453:epidemiology* / Q000235:genetics / Q000635:transmission; D013297:Streptococcus pyogenes / Q000145:classification / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D005098:Exotoxins; D008565:Membrane Proteins; C117980:SpeA protein, Streptococcus pyogenes; C027951:erythrogenic toxin; C082385:nephritis plasmin binding protein, Streptococcus; C014689:streptococcal M protein; D003546:Cysteine Endopeptidases; D020170:Caspase 1