Strep pyogenes: Overview
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Bacteria - Gram Positive
- Staph aureus: Overview
- Staph aureus: Presentation
- Methicillin-Resistant Staph aureus (MRSA)
- Staph saprophyticus
- Strep pneumoniae: Overview
- Strep pneumoniae: Presentation
- Strep viridans
- Strep pyogenes: Overview
- Strep pyogenes: Presentation
- Strep agalactiae
- Strep bovis
- Enterococcus
- Bacillus anthracis
- Bacillus cereus
- Clostridium tetani
- Clostridium perfringens
- Clostridium botulinum
- Clostridium difficile
- Corynebacterium diphtheriae
- Listeria monocytogenes
- Nocardia
- Actinomyces
Streptococcus pyogenes overview
- Part of Group A streptococci (GAS)
- Characteristics
- Gram + cocci in chains
- Catalase -
- First step in gram positive cocci; determines staph (catalase positive) vs. strep
- Beta-hemolytic
- Second step, narrows type of strep
- Pyrrolidonyl arylamidase (PYR) +
- Because the bacitracin test is not very specific for S pyogenes, it has been replaced in many laboratories by the pyrrolidonyl arylamidase (PYR) test
- Bacitracin sensitive
- Has been widely replaced with the PYR test
- Virulence Factors
- Hyaluronic acid capsule
- Protein M
- Main virulence factor for strep. pyogenes
- Inhibits phagocytosis and activation of complement
- Also cytotoxic to neutrophils and mediator of bacterial attachment
- Streptolysin (Hemolysin) O
- Lyses RBCs (causing beta-hemolysis) and polymorphonuclear leukocytes.
- Anti-streptolysin O (ASO) titers used as marker of recent infection
- Pyrogenic exotoxin
- Pyrogenic = causes fever; cause of Scarlet fever
- Superantigen that results in tissue injury and septic shock; e.g. Toxic shock syndrome
- Streptokinase
- Fibrinolytic (clot-buster) that is now used as a medication
- Enables more spread from initial site of infection
- DNAse
- DNase is an extracellular enzyme that depolymerizes viscous DNA in pus and disintegrates polymorphonuclear leukocytes, allowing the streptococcus to move more freely in the tissue.
- Anti-DNAse is also a titer measured as a marker of recent infection