![]() The most important known mechanisms implicated in GAS macrolide resistance are a 14- and 15-membered ring macrolide-specific efflux (M phenotype), encoded by the mef(A) gene, as well as the modification of the ribosomal target by a methylase encoded by the erm(B) or the erm(TR) gene the latter is currently referred to as erm(A) or erm(A) subclass erm(TR) gene. This system has already been used to analyze the GAS epidemiology in the Pacific region, which is characterized by a great variety of circulating emm types. The emm cluster system is expected to guide vaccine design when attempting to predict vaccine efficacy. It adds valuable information regarding tissue tropism and immune response to GAS infections in various settings on a worldwide level. Recently, an emm cluster system based on strong phylogenetic support has been described, which serves as a functional classification scheme for GAS M proteins. N-terminal M protein peptides evoke protective antibodies against epidemiologically important GAS types with the greatest bactericidal activity. Ī protein-based multivalent type-specific GAS vaccine containing amino-terminal M peptides from 30 different emm types has been developed. More than 220 emm types have been recognized to date. ![]() The gene encoding M protein, emm, is the basis for sequence typing used to differentiate among strains of GAS this differentiation is founded on relatively minor sequence differences in the 5ʹ regions of the gene. The M protein of GAS is a surface protein, which constitutes a major virulence factor as well as the major immunologic epitope of GAS it possesses a hypervariable region of the amino-terminal, 40 to 50 amino acid residues. Streptococcus pyogenes infections are a major cause of morbidity and mortality worldwide and are responsible for a diverse array of noninvasive, invasive and immune-related diseases.
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