Chapter 51 - Streptococcal superantigenic toxins

Abstract

Streptococcus pyogenes is a Gram-positive commensal bacterium that colonizes human tissue. When the host immune system is compromised or when the bacteria are able to penetrate the physical barrier of the skin, S. pyogenes can cause a wide range of diseases. Penetration of the skin barrier by GAS can cause bacteremia and severe invasive deep tissue infections, such as cellulitis, myositis, and necrotizing fasciitis. The most severe form of invasive infection results in clinical symptoms similar to staphylococcal toxic shock syndrome and was therefore described as streptococcal toxic shock syndrome (STSS). It is widely believed that the resurgence of invasive GAS infections is the result of an interplay between changes in bacterial virulence and host susceptibility. This chapter discusses a large number of secreted proteins (over 30) comprising the streptococcal superantigens and virulence factors including several adhesion molecules. GAS is associated with a number of severe invasive diseases, including cellulitis, myositis, and necrotizing fasciitis. Several lines of epidemiological, experimental, and clinical observations strongly imply that at least some SAgs play a pivotal role in the pathogenesis of STSS and possibly in other invasive GAS diseases.