All are true about streptococcus except:: (A) M-protein is responsible for production of mucoid colonies, (B) M- protein is responsible for virulence, (C) Mucoid colonies are virulent, (D) No resistance to penicillin has been reported
Answer is A. Mucoid colonies are due to production of capsule of hyaluronic acid not due to M-protein. Growth characteristic of strep. Pyogenes:
On blood agar virulent stains form matt or mucoid colones while avirulent from glossy colonies.
M, T, R are proteins found on outer part of cell wall and forms the basis of Griffith classification.
M protein – acts as virulence factor and antibody against it are protective.
T and R protein – No relation to virulence