Journal Article

Distribution of Streptococcal Inhibitor of Complement Variants in Pharyngitis and Invasive Isolates in an Epidemic of Serotype M1 Group A Streptococcus Infection

Nancy P. Hoe, Jaana Vuopio-Varkila, Martti Vaara, Diana Grigsby, David De Lorenzo, Yun-Xin Fu, Shu-Jun Dou, Xi Pan, Kazumitsu Nakashima and James M. Musser

in The Journal of Infectious Diseases

Published on behalf of Infectious Diseases Society of America

Volume 183, issue 4, pages 633-639
Published in print February 2001 | ISSN: 0022-1899
Published online February 2001 | e-ISSN: 1537-6613 | DOI:

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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.

Journal Article.  4204 words.  Illustrated.

Subjects: Infectious Diseases ; Immunology ; Public Health and Epidemiology ; Microbiology