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The M-protein genes (emm genes) of 103 separate impetiginous Streptococcus pyogenes isolates were sequenced and the sequence types were compared to the types obtained by Vir typing. Vir typing is based on restriction fragment length polymorphism (RFLP) analysis of a 4- to 7-kb pathogenicity island encoding emm and other virulence genes. By using both HaeIII and HinfI to generate RFLP profiles, complete concordance between Vir type and emm sequence type was found. Comparison of the emm sequences with those in GenBank revealed new sequence types sharing less than 90% identity with known types. Diversity in the emm sequence was generated by corrected frameshift mutations, point mutations, and small in-frame mutations.

Group A streptococcal infections among the Aboriginal communities of the Northern Territory of Australia are endemic, with a concurrently high rate of the postinfection sequelae of rheumatic fever and acute post-streptococcal glomerulonephritis. The majority of the group A streptococcal isolates from the Northern Territory are not typeable by M typing. We recently developed a novel genotyping method, Vir typing. A preliminary study using this method discriminated all the M-nontypeable (MNT) isolates. Vir typing is based on restriction fragment length polymorphisms of the 4- to 7-kb Vir regulon of group A streptococci, which contains a number of genes, including emm (the gene for M protein). A total of 407 isolates of group A streptococci obtained from four Aboriginal communities over a 4-year period were typed by this genotyping method. Forty-two distinct genotypes were found among the isolates, including 22 among the MNT isolates. The correlation between Vir type and M type was good. This genotyping method allows the characterization of all group A streptococcal isolates from Aboriginal communities in the Northern Territory. We also propose that Vir typing be used in conjunction with M typing for epidemiological surveillance in geographical regions where the majority of isolates are MNT.