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9 Cards in this Set
- Front
- Back
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What are streptococci?
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They are Gram+ spherical cocci arranged in chains or pairs. All are catalase negative. Staph are positive.
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What are alpha hemolytic strep?
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They are streptococci that form a green zone around their colonies as aresult of incomplete lysis of RBCs in the agar.
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What are beta hemolytic strep?
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They form a clear zone around their colonies because complete lysis of the red cells.
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Beta hemolysis is due to what?
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It is due to the production of enzymes(hemolysins) called streptolysin O and Streptolysin S.
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Are some strep nonhemolytic?
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Yes. This is gammahemolysis.
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What are the two important antigens of beta hemolytic streptococci. What are they?
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C carbohydrate
M protein |
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What is C carbohydrate?
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It determines the group of beta hemolytic streptococci. It is in the cell wall, and determined by an amino sugar.
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What is the M protein?
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It is the most important virulence factor and determines the type of group A beta hemolytic streptococci. It protrudes from the outer surface of the cell, and interferes with the ingestion by phagocytes, it is antiphagocytic.
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How many serotypes are based on the M protein?
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App. 80.
Some types are rheumatogenic, cause rheumatic fever, whereas strains of S. pyogenes that produce other M protein types are nephritogenic, cause acute glomerulonephritis. |
