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14 Cards in this Set
- Front
- Back
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General characteristics of Streptococcus
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- G+ cocci
- arranged in pairs or chains - most are facultative - complex nutritional requirements - catalase - (differentiates from streptococcus) - |
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classified by three overlapping schemes
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- serologic properties or lancefield groupings
- hemolytic patterns - biochemical properties |
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lancefield or serologic groupings
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- distinguished by major cell wall carbohydrate
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alpha hemolysis
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- green hue from partial hemolysis
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beta hemolytic
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- clearing, complete lysis
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gamma hemolytic
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- no lysing
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Group A Strep
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- mucous membranes and on skin
- pharyngitis- strep throat - skin infections- pyoderma, cellulitis, necrotizing fascitis, toxic shock syndrome |
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pharyngitis and complicatoins
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- GAS (group a strep)
- 70% of all cases - otitis media and sinusitis - scarlet fever - rheumatic fever, autoimmune - acute glomerulonephritis- protein M form Ab complex |
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who does GAS primarily infect
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children from 5-15
can colonize nasopharanyx of healthy people transiently |
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adherence factors
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- virulence factors
- lipotechoic acid mediates attachement to epi cells - protein F binds fibronectin |
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immunoavoidance factors
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- virulence factors
Protein M - antiphagocytic - disrupts complement - cause rheumatic fever - autoimmune issues - common epitopes with brain and heart - M like proteins |
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S. pyogenes immunoavoidance virulence factor
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-Hyaluronic acid capsule
- similar to host connective tissue - prevents phagocytosis |
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virulence of GAS
- toxins and enzymes |
- streptolysis (O and S are hemolytic and leukotoxic)
- O is antigenic - oxygen labile, - S is oxygen stable |
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SpeA, B and C exotoxins
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- superantigens
- activates lots of cytokines |
