Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
11 Cards in this Set
- Front
- Back
|
A second method to differentiate streptococci from staphylococci invoves the enzyme catalse.
Which of these two results in a catalase positive test? |
Staphylococci possess the enzyme "catalse", whereas streptococci do not. (both are gram positive coccus)
Staphylococci are thus referred to as catalse positive and strep are catalse negative. |
|
|
Catalse rx. and Catalse test.
|
Converts H2O2 into H2O and O2. To test for catalse, a wire loop is rubbed a cross a colony of gram + cocci and mixed on a slide with H2O2. If bubbles appear, the enzyme catalase must be present, and so staphylococci are present.
|
|
|
Classification of streptococci
|
Streptococci are divided into 3 groups based on their specific hemolytic ability: Beta-hemolytic, Alpha-hemolytic, and gamma hemolytic.
The streptococci can also be classified based on the antigenic characteristics of the C carbohydrate (a carbohydrate found on the cell wall) (also known as Lancefield antigens) lettered A, B, C, D, E through S). |
|
|
Beta-Hemolytic Streptococci
|
Completely lyse the RBCs, leaving a clear zone of hemolysis around the colony.
|
|
|
Alpha-Hemolytic Streptococci
|
only partially lyse the RBCs, leaving a greenish discoloration of the culture medium surrounding the colony. This discolored area contains unlysed RBCs and a green-colored metabolite hemoglobin.
|
|
|
Gamma-Hemolytic streptococci
|
Are NOT able to hemolyze the RBCs, and therefore we should really not use the word "hemolytic" in this situation (often referred to as non-hemolytic)
|
|
|
The differentiation of Th1 cells from Th0 cells is markedly enhanced by
|
IL-12 (from macrophages) and Interferon Gamma (from TH1 and NK cells)
|
|
|
The differentiation of Th2 cells from Th0 cells is markedly enhanced by
|
IL-4 (from Th2 cells or NK T cells).
|
|
|
IL-4, IL-10 (from Th2 cells) and TGF-b (from CD4+ cells)
|
inhibit the generation of Th1 cells
|
|
|
Interferon-gamma inhibits what?
|
Th2 cell proliferation
|
|
|
Th2 cell proliferation is inhibited by?
|
Interferon Gamma
|
