Analysis of DNA corresponding to group A streptococcal A- and B-regions of M protein by restriction fragment length polymorphism

The emm gene amplicons encoding the N- and partial C-terminal regions of the M protein from Group A streptococcus (GAS) isolates were amplified by PCR and digested with a restriction endonuclease, AluI. Digested PCR products were then resolved by polyacrylamide gel electrophoresis. Using one pair of primers, 13 known GAS M types showed one to four bands of PCR products. Digested with AluI, they exhibited different restriction RFLP patterns. Of 106 GAS isolates examined from normal population and patients with GAS-associated complications, 95 isolates showed RFLP patterns that corresponded to the 13 known M types. The other 11 isolates demonstrated different RFLP patterns other than the known M types. They were then analyzed by DNA sequencing and other six M types were obtained. In addition, M93 GAS was the most common from the population studied, which is consistent with a previous study of Thai GAS isolates. This PCR-RFLP protocol has the potential for the rapid screening of GAS emm types, and would be able to characterize the number of C-region in different types of GAS. This method is considerably advantageous as an alternative M typing approach for epidemiological studies in developing countries in which GAS is endemic and DNA sequencer and budgets are limited.