Journal Article

Identification of superantigen genes speM, ssa, and smeZ in invasive strains of beta-hemolytic group C and G streptococci recovered from humans

Emeka I. Igwe, Patricia L. Shewmaker, Richard R. Facklam, Monica M. Farley, Chris Van Beneden and Bernard Beall

in FEMS Microbiology Letters

Volume 229, issue 2, pages 259-264
Published in print December 2003 |
Published online January 2006 | e-ISSN: 1574-6968 | DOI:

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Group C and G Streptococcus dysgalactiae subspecies equisimilis (GCSE and GGSE) cause a substantial percentage of invasive disease caused by beta-hemolytic streptococci. To determine whether Streptococcus pyogenes superantigen (SAg) genes commonly exist within these organisms, 20 recent invasive GCSE and GGSE human isolates and one group G Streptococcus canis human isolate were tested for the presence of SAg genes speH, speJ, speL, speM, ssa and smeZ by polymerase chain reaction (PCR). Prior to this work, sequence-based evidence of the speM, ssa, and smeZ genes in GCSE, GGSE, and S. canis had not been documented. Eleven of the 21 isolates were PCR-positive for the presence of one to two of the SAgs speM, ssa, or smeZ, with four of these isolates carrying ssa+speM or ssa+smeZ. No isolate was positive for speH, speJ and speL. All six ssa-positive GGSE strains harbored the ssa3 allele, previously only found among S. pyogenes strains. All three smeZ-positive GGSE isolates carried one of two smeZ alleles previously only found within S. pyogenes, however the single S. canis isolate carried a new smeZ allele. All five GCSE and GGSE speM-positive isolates harbored a newly discovered speM allele. The identification of these SAgs within S. dysgalactiae subsp. equisimilis and S. canis with identical or near-identical sequences to their counterparts in S. pyogenes suggests frequent interspecies gene exchange between the three beta-hemolytic streptococcal species.

Keywords: Group C streptococcus; Group G streptococcus; Superantigen; Streptococcal pyrogenic exotoxin

Journal Article.  3260 words.  Illustrated.

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