How exactly does Streptococcus pyogenes cause the necrotising fasciitis infection?
It’s the toxins released by S. pyogenes that cause the trouble. The toxins directly kill tissue, interfere with blood flow to the tissue and break down the tissue, which rapidly spreads the bacteria and can lead to widespread effects such as shock. What you’re specifically asking for is the pathophysiology of the disease, which is complex. In the first place, consider the virulence factors of Group A streptococci: (1) M protein, fibronectin-binding protein (Protein F) and lipoteichoic acid for adherence; (2) hyaluronic acid capsule as an immunological disguise and to inhibit phagocytosis; M-protein to inhibit phagocytosis (3) invasins such as streptokinase, streptodornase (DNase B), hyaluronidase, and streptolysins; (4) three types of exotoxins, such as pyrogenic (erythrogenic) toxin. It’s a simple matter of following the trail.
