FALSE statement about the Streptococcus is:
Strains with well marked capsules produce mucoid colonies. Streptococcus pyogenes can be typed based on surface proteins to M,T,R. M protein is most impoant of these. It act as a virulence factor by inhibiting phagocytosis. It is antigenic and antibody to this promotes phagocytosis of coccus. M protein is heat labile and acid stable but susceptible to tryptic digestion. Also know: Pyrogenic exotoxins (erythrogenic, dick, scarlatinal toxin) -dick test is used to identify children susceptible to scarlet fever, a type of acute pharyngitis with erythematous rash. The M protein itself is a fibrillar coiled-coil molecule with structural homology to myosin. Its carboxy terminus is rooted in the peptidoglycan of the cell wall, and the amino-terminal regions extend out from the surface. The specificity of the multiple serotypes of M protein is determined by variations in the amino sequence of the amino-terminal poion of the molecule. Antigenicity and functions differ in domains of the molecule. There are more than 80 M protein serotypes present. Ref: Ray C.G., Ryan K.J. (2010). Chapter 25. Streptococci and Enterococci. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.
M protein is responsible for production of mucoid colonies
M protein is the major surface protein of group A streptococci
Mucoid colonies are virulent
Endotoxin causes rash of scarlet fever