The emm-pattern and tissue tropism for these M types were also predicted and compared based on the emm-cluster classification.
A complementary typing system, emm-pattern typing, is based on the presence and arrangement of emm and emm-like genes located in the mga locus within the S.pyogenes genome.
The emm gene encodes the M protein, and emm typing based on the nucleotide sequence encoding the 50N-terminal amino acids (aa) of the mature protein is a major epidemiological tool in surveys on GAS, GCS and GGS.
A sequence-based typing system called emm sequence typing, based on the N-terminus hypervariable region (5') of the M protein gene, is now widely used [ 4].
Group A Streptococci (GAS) are classified into 180 emm-types based on the sequence of the amino-terminal hyper-variable region of the M surface protein.
emm typing for both GAS and GGS is based on the heterogeneity of the 5´ ends of the gene, which give rise to different sequence types.
The emm-cluster classification of the strains identified in this study was based on the new functional classification recently proposed by Sanderson-Smith et al. [ 9].
GAS strains are classified based on the aminoterminal sequence of the M protein, a polymorphic cell-surface adhesin and anti-phagocytic factor encoded by the emm gene.
A GAS vaccine under trial that is based on the amino-terminus of the M protein provides type-specific immunity, and hence seems ineffective in India because of heterogeneous emm types.
