What is the pathophysiology of group A streptococcal (GAS) infection?

Updated: Sep 07, 2018
  • Author: Zartash Zafar Khan, MD, FACP; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Answer

S pyogenes tends to colonize the upper respiratory tract and is highly virulent as it overcomes the host defense system. The most common forms of S pyogenes disease include respiratory and skin infections, with different strains usually responsible for each form.

The cell wall of S pyogenes is very complex and chemically diverse. The antigenic components of the cell are the virulence factors. The extracellular components responsible for the disease process include invasins and exotoxins. The outermost capsule is composed of hyaluronic acid, which has a chemical structure resembling host connective tissue, allowing the bacterium to escape recognition by the host as an offending agent. Thus, the bacterium escapes phagocytosis by neutrophils or macrophages, allowing it to colonize. Lipoteichoic acid and M proteins located on the cell membrane traverse through the cell wall and project outside the capsule.


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