cMLS and M phenotypes among Streptococcus pyogenes isolates in Chennai.

Group A Streptococcus associated diseases continue to be a major public health problem. Asymptomatic carriage of GAS is prevalent in school children. Penicillin remains the drug of choice for GAS infections; alternate therapies include macrolides and cephalosporins. Though resistance to penicillin has never been reported, resistance to macrolides and lincosamides is being increasingly reported in several parts of the world as in France, Italy, Slovenia and Pittsburgh. Macrolide lincosamide susceptibility phenotype patterns have been found to be associated with specific genotypes of erythromycin resistant strains. The M phenotype is associated with the mef gene that encodes a membrane protein responsible for efflux-mediated resistance and the MLS phenotypes are associated with the erm gene, which encodes methylases responsible for resistance. The phenotypes can be identified by a simple double disc diffusion method. In this study we have identified the erythromycin resistant phenotypes present in school children in Chennai.