MOLECULAR EPIDEMIOLOGY OF IMPETIGINOUS GROUP-A STREPTOCOCCAL INFECTIONS IN ABORIGINAL COMMUNITIES OF NORTHERN AUSTRALIA

Group A streptococcal infections among the Aboriginal communities of t he Northern Territory of Australia are endemic, with a concurrently hi gh rate of the postinfection sequelae of rheumatic fever and acute pos tstreptococcal glomerulonephritis. The majority of the group A strepto coccal isolates from the Northern Territory are not typeable by M typi ng. We recently developed a novel genotyping method, Vir typing. A pre liminary study using this method discriminated all the M-nontypeable ( MNT) isolates. Vir typing is based on restriction fragment length poly morphisms 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 Abor iginal communities over a 4-year period were typed by this genotyping method. Forty-two distinct genotypes were found among the isolates, in cluding 22 among the MNT isolates. The correlation between Vir type an d M type was good. This genotyping method allows the characterization of all group A streptococcal isolates from Aboriginal communities in t he Northern Territory. We also propose that Vir typing be used in conj unction with M typing for epidemiological surveillance in geographical regions where the majority of isolates are MNT.