High-Resolution Genotyping of Streptococcus pyogenes

The numerous virulence factors of Streptococcus pyogenes (group A streptococcus, GAS) allow it to produce a wide range of diseases in man. One of these is the filamentous M protein encoded by the emm gene which is the basis of the Lancefield serotyping scheme. Nucleotide sequences for emm genes have been determined and can be amplified by polymerase chain reaction (PCR) with universal primers [4] for restriction fragment length polymorphism (RFLP) analysis. GAS produce several antigenically distinct streptococcal pyrogenic exotoxins (SPEs). The occurrence of different spe genes can be studied with respect to their epidemiology or population genetics. We have previously defined genotyping methods to subtype strains both between and within prevalent M serotypes [5]. In the present study, we have used these and additional molecular methods to ask how high resolution genotyping alters or improves the classical phenotypic (M protein-based) epidemiological study of GAS outbreaks. We have also asked how this approach would perform as a tool for population genetics analysis, in this case of serotypes M1 and M5.