top of page

Microbiology Glossary

Virulence Factors

  • Adherence factor: allows for better adherence to squamous epithelial cells of urogenital tract (not skin or mucosa) than other catalase neg staph.

  • Alpha- hemolysin​: lyse rbcs & damages platelets and macrophages

  • Beta- hemolysin: "hot-cold" lysin; acts on the plasma membrane of rbcs

    • enhances Beta- hemolysis (make CAMP test work)​

    • lethal to polynucleated WBCs

    • contributes to invasiveness of S. aureus

    • associated with severe cutaneous infections & necrotizing pnuemonia

  • CAMP factor:

  • Capsule: protects bacteria from phagocytosis

  • Catalase: enzyme

  • Coagulase: enzyme

  • Cytolytic Toxins:​

    • Includes alpha-, beta- and gamma- hemolysins

  • Enterotoxin

  • Exfoliative Toxin:

    • Causes SSS & Ritter's Disease​

    • Also causes bullous impetigo

  • Gamma- hemolysin: only in association with Panton-Valentine leucocidin (PVL) in community acquired S. aureus 

  • Hemolysis:

  • Hyaluronidase: also known as "spreading factor"

    • an enzyme that ​dissolves the the hyaluronic acid found in connective tissues

  • ​

  • Lipase​​​: enhance spread of infection by working on lipids on skin & oil glands (sebaceous glands)

  • M Protein: 

  • Protein A:

    • Help bind the Fc portion of IgG preventing phagocytosis & negate protective effect of IgG​​

  • Pyrogenic Exotoxins: (4 types)

    • causes a spreading rash in Scarlet Fever​

    • functions as a "super antigen"

    • have the ability to stimulate a strong T-cell proliferation

    • not all Strep A have one or all 4 of these

  • Sialic Acid: in addition to a capsule, it help bacteria evade innate immune response of host

  • Streptokinase: Lyses fibrin clots

  • Streptolysin O: 

    • causes the beta hemolysis anaerobically​

    • oxygen labile

    • destroys platelets, WBCs, & RBCs

    • Serologic test, ASO, tests for antibodies against it

  • Streptolysin S

bottom of page