Multiple strains of Streptococcus pyogenes in skin sores of aboriginal Australians.

A molecular technique (random amplification of polymorphic DNA) was used to characterize group A streptococcal (GAS) strains among 194 isolates from 55 swabs from 12 Australian Aboriginal children and adults with multiple pyoderma lesions. Ninety-three percent of the lesions contained only one strain of GAS, but 8 of 12 individuals were infected with more than one strain. We conclude that accurate epidemiologic surveys require that more than one swab specimen be obtained from each person, whereas typing of more than one colony per swab is less informative. Characterization of GAS strains by random amplification of polymorphic DNA analysis should help to provide important insights into the epidemiology of GAS, particularly in tropical populations where many isolates are M nontypeable, and into the mechanisms of genetic variation of GAS in such populations.