Streptococcus pyogenesstrains containingemm12 andemm55 possess a novel gene coding for distantly related SIC protein

Streptococcus pyogenesinfection and acute glomerulonephritis (AGN), a non-suppurtave disease, are endemic in the Aboriginal people of the Northern Territory (NT) of Australia. Vir typing, a locus-specific polymerase chain reaction (PCR)-based typing method [Gardiner, Hartas, Currieet alPCR Meth Appl19954: 288–93], has revealed high divergence among the NT streptococcal strains. A total of 76 Vir types (VTs) representing about 95% of the NT isolates were screened forsic, a gene for streptococcal inhibitor of complement function, by PCR and hybridization. This revealed that seven VTs are positive forsic, and there are two classes of the gene: those closely related tosic(CRS) originally described by Akesson, Sjoholm & Bjorck [J. Biol. Chem.1996271: 1081–8] and those distantly related tosic(DRS). Among the CRS-positive VTs, VT16, VT78 and VT91 haveemm(gene for M protein) encoding type 1 M protein or related specificity, and VT8 and VT101 containemm57 or related alleles. Chromosomal location of CRS inemm57 is different from that inemm1 or related strains. The DRS-positive VT18 and VT52 containedemm55 andemm12 respectively, which are phylogenetically related. Strains ofS. pyogenestypes 1, 12, 55 and 57 are known to be associated with AGN. Restricted distribution of CRS and DRS among the M types historically associated with AGN suggests that thesesicalleles may have a role in AGN pathogenesis.