​Infectious Diseases and Microbiology - Streptococcus pharyngitis ( Streptococcus pyogenes)

​Infectious Diseases and Microbiology - Streptococcus pharyngitis ( Streptococcus pyogenes) 
This bacterium is gram-positive, belongs to the Lancefield group A, is catalase-negative, beta hemolytic, and bacitracin-sensitive; it also has 80 different serotypes determined by the M protein.
Direct touch and breathing droplets are the vectors of transmission. Cuts and scrapes are the entry points for skin infections.
 Children often experience pharyngitis. A "strawberry" tongue, fever, and a widespread rash are the hallmarks of scarlet fever. Impetigo, erysipelas, and necrotizing fasciitis are infections of the skin and soft tissues.
Sepsis and streptococcal toxic shock syndrome are forms of systemic symptoms. As a result of an infection, rheumatic fever and acute glomerulonephritis can develop.

Spore A, Spore B, and Spot C are erythrogenic superantigen toxins; C5a peptidase, hyaluronidase, streptokinase, DNase, streptolysin S, and streptolysin O are streptolytic enzymes; and the hyaluronic acid capsule, M protein, F protein, and M-like proteins are structural components of the virus. Autoantibodies targeting M proteins cause rheumatic fever when they bind to cardiac muscle. The buildup of immunological complexes causes acute glomerulonephritis.
 S pyogenes is susceptible to bacitracin, has no catalase, and breaks the blood clots. 

When diagnosing pharyngitis, the quick strep test comes in handy. Culture is done when fast strep tests come back negative. In individuals suffering from rheumatic fever or acute glomerulonephritis, anti-streptolysin O antibodies (ASO) can be helpful in confirming the presence of previous S pyogenes infections.
Pharyngeal infections, rather than cutaneous infections, typically result in elevated ASO titers.

The majority of S. pyogenes infections can be effectively treated with penicillin and erythromycin. Surgical excision of infected deep skin may be necessary. People who have had rheumatic fever in the past can avoid additional heart damage by taking antibiotics as a preventative measure.