Streptococcal Skin Infections M protein Fibrils lacking on fibrils M protein 。 Streptococcus pyogenes 。Group a beta- hemolytic streptococci ·M proteins Figure 21.5 • Streptococcus pyogenes • Group A beta￾hemolytic streptococci • M proteins Streptococcal Skin Infections Figure 21.5