Cell Wall and Surface Molecules: Capsule

Excerpt

In the 1920s, it was recognized that a mucoid or matte colony phenotype of Streptococcus pyogenes was associated with virulence in mice and with resistance to killing by human blood leukocytes. The gelatinous material produced by the mucoid isolates, currently known as capsule, was later characterized as hyaluronic acid, a linear polymer of N-acetylglucosamine and glucuronic acid with a high molecular mass that is structurally identical to hyaluronic acid found in the extracellular matrix of many higher animals, including human beings. It is now recognized that most (but not all) clinical isolates of group A streptococci produce hyaluronic acid, which is associated with the cell surface during exponential growth and shed during stationary phase. This chapter presents a summary of information on the capsule of Streptococcus pyogenes, its biochemistry, genetics, and role in virulence.