title: Identification of superantigen genes speM, ssa, and smeZ in invasive strains of beta-hemolytic group C and G streptococci recovered from humans.
abstract: 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.
authors.affiliation: Centers for Disease Control and Prevention, Respiratory Diseases Branch, 1600 Clifton Rd, Mailstop CO2, 30333, Atlanta, GA, USA
authors.forename: Emeka I
authors.initials: EI
authors.lastname: Igwe
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Shewmaker
authors.forename: Richard R
authors.initials: RR
authors.lastname: Facklam
authors.forename: Monica M
authors.initials: MM
authors.lastname: Farley
authors.forename: Chris
authors.initials: C
authors.lastname: van Beneden
authors.forename: Bernard
authors.initials: B
authors.lastname: Beall
mesh_terms: D000942:Antigens, Bacterial / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics; D001427:Bacterial Toxins / Q000235:genetics*; D005098:Exotoxins / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D013290:Streptococcal Infections / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000235:genetics*; D018089:Superantigens / Q000235:genetics*
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D005098:Exotoxins; C423447:SpeJ protein, Streptococcus pyogenes; C469921:SpeM protein, Streptococcus pyogenes; D018089:Superantigens; C107894:mitogenic exotoxin Z protein, Streptococcus; C457360:speL protein, Streptococcus pyogenes; C117321:streptococcal superantigen SSA