Distribution of streptococcal inhibitor of complement variants in pharyngitis and invasive isolates in an epidemic of serotype M1 group A Streptococcus infection.
Streptococcal inhibitor of complement (Sic) is a highly polymorphic extracellular protein made predominantly by serotype M1 group A Streptococcus (GAS). New variants of the Sic protein frequently appear in M1 epidemics as a result of positive natural selection. To gain further understanding of the molecular basis of M1 epidemics, the sic gene was sequenced from 471 pharyngitis and 127 pyogenic and blood isolates recovered from 598 patients living in metropolitan Helsinki, Finland, during a 37-month population-based surveillance study. Most M1 GAS subclones recovered from pyogenic infections and blood were abundantly represented in the pool of subclones causing pharyngitis. Alleles shared among the pharyngitis, pyogenic, and blood samples were identified in throat isolates a mean of 9.8 months before their recovery from pyogenic infections and blood, which indicates that selection of most sic variants occurs on mucosal surfaces. In contrast, no variation was identified in the emm and covR/covS genes.
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Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 S. 4th St., Hamilton, Montana 59840, USA.
Vuopio-Varkila
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J
Vaara
M
M
Grigsby
D
D
De Lorenzo
D
D
Fu
Y X
YX
Dou
S J
SJ
Pan
X
X
Nakashima
K
K
Musser
J M
JM
D000483:Alleles; D000595:Amino Acid Sequence; D000942:Antigens, Bacterial; D016470:Bacteremia / Q000453:epidemiology* / Q000382:microbiology; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics; D003169:Complement Inactivator Proteins / Q000235:genetics / Q000378:metabolism; D004196:Disease Outbreaks; D005387:Finland / Q000453:epidemiology; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008969:Molecular Sequence Data; D010612:Pharyngitis / Q000453:epidemiology* / Q000382:microbiology; D010802:Phylogeny; D011159:Population Surveillance; D012703:Serotyping; D013290:Streptococcal Infections / Q000453:epidemiology* / Q000382:microbiology; D013297:Streptococcus pyogenes / Q000145:classification / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D014774:Virulence / Q000235:genetics
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D003169:Complement Inactivator Proteins; C097739:SIC protein, Streptococcus; C014689:streptococcal M protein