EVALUATION OF METHODS FOR EPIDEMIOLOGIC TYPING OF GROUP-A STREPTOCOCCI

Serotyping is widely used for epidemiologic investigation of group A s treptococci (GAS). To evaluate molecular typing methods of GAS, restri ction endonuclease analysis (REA) of genomic DNA and analysis of DNA r estriction fragment length polymorphism of rRNA genes (ribotyping) wer e used in parallel with serotyping. The genomic DNA of 239 epidemiolog ically unrelated GAS isolates from human invasive infections was diges ted with HindIII restriction enzyme. Both REA and ribotyping different iated subclasses within serotypes. However, they did not consistently differentiate between isolates of different serotypes. Ribotyping was less discriminatory than REA. Within the T1M1 serotype, often associat ed with invasive GAS infections, 92% of the REA patterns were identica l, suggesting a common origin for these isolates. Most other serotypes studied were more heterogenic. Among 32 isolates nontypeable by serot yping, 11 distinct REA patterns and 5 ribotypes were identified. REA a nd ribotyping are useful supplementary tools for classification of GAS and can add to the discriminatory power of serotyping.