Infections due to group A streptococcus: new concepts and potential treatment strategies

Important new information has been gained on the pathogenesis and treatment of life-threatening invasive infections caused by group A streptococci (GAS), i.e. the streptococcal toxic shock syndrome (STSS) and necrotizing fasciitis (NF). Both STSS and NF lead to superantigen reactions with activation of up to 10% of the CD4+ lymphocytes and release of large amounts of cytokines; mainly tumour necrosing factor beta, interferon gamma, interleukin 1 and interleukin 6. Streptococcal products known to trigger the superantigen reactions are the pyrogenic exotoxins, spe A, spe B and spe C and the M-proteins. Therapeutically clindamycin has been shown to reduce mortality in animal experiments in comparison to penicillin treatment. A possible mechanism is the effect of clindamycin on protein synthesis which might decrease the production of superantigens. In man, the use of intravenous immunoglobulin has been shown to significantly reduce mortality in STSS and NF. The most probable mechanism is neutralisation of superantigens by antibodies in the immunoglobulin preparations used.