Group A Streptococci: hyaluronic acid capsule

• all Group A Streptococci have the same capsule

• hyaluronic acid is a glycosaminoglycan, a component of all joint capsules

• this is a stealthy way to avoid our immune system—human hosts cannot afford to make antibody against something found in the joint because it would be very deleterious to our tissues

Group A Streptococci hyaluronic acid capsule mediates invasion via CD44

• mimics component of ECM and uses it to mediate attachment

Group A Streptococci fibronectin-binding proteins

• bacteria bind to matrix molecules

• matrix molecules bind to integrins on a host cell

• this anchors Strep

Sfb1, a Group A Streptococci fibronectin-binding protein

Group A Streptococci makes superantigens and leads to streptococcal toxic shock syndrome

• clonal expansion of T cells leads to scarlet fever

• if we purify toxin and put it into an animal, get renal and hepatic necrosis

Category: Microbiology Notes