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23 Cards in this Set
- Front
- Back
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What is septic shock?
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Sepsis that results in dangerous drops in blood pressure and organ dysfunction. It is also referred to as endotoxic shock b/c endotoxin often triggers the immune response that results in sepsis and shock.
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What is tumor necrosis factor?
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It is an endogenous mediator of sepsis. It is also called cachectin, b/c it is released from tumors, producing a wasting syndrome, called cachexia, in cancer patients.
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Does TNF trigger the release of other substances?
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TNF triggers the release of the cytokine, interleukin-1, from macrophages and endothelial cells, which in turn triggers the release of others cytokines and prostaglandins.
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What is catalase, and what bacteria possess it?
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Catalase is used by one method to differentiate streptococcus from staphylococcus. Staph species possess the enzyme catalase and strep species do not. staph are called catalase positive.
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What else does catalase do and how can one test for it?
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Catalase converts H2O2(which is used by macrophages and neutrophiles) into H2O and O2. To test for it, a wire loop is rubbed across a colony of gram + cocci and mixed on a slide with H2O2. If bubbles appear, the enzyme catalase must be present, which confirms the presence of Staph species.
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How are Strep. species classified?
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Certain species of streptococci can either completely or partially hemolyze RBC. Three groups are recognized;
Beta hemolytic Alpha hemolytic Gamma non-hemolytic. |
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Define each of these classifications.
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Beta h.- the strep completely lyse RBC, leaving a clear zone of hemolysis around the colony.
Alpha h.- RBC are partially lysed, leaving a greenish discoloration of the culture medium. The discolored area represents unlysed RBC and a green colored metabolite of hemoglobin. Gamma-non-hemolytic; strep are unable to lyse the RBC. |
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What are Lancefield antigens?
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Strep can also be classified based on the antigenic characteristics of the C carbohydrate(found on the cell wall). These antigens are given letter names from A,B,C,D,E through S.
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Are all of these antigen groups significant?
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Although there are more than 30 species of streptococci, only 5 are significant human pathogens. Three of these pathogens have lancefield antigens, groups A, B, and D.The other 2 do not have Lancefield antigens, and are called by their species names. One is Strep. pneumoniae and the other is actually a big group of streptococci collectively called the Viridans group streptococci.
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What is meant by Group A Beta- Hemolytic Streptococci?
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These organisms are so named b/c they possess the Lancefield group A antigen and are Beta hemolytic on blood agar. They are also called Strep. pyogens, which means pus producing and cause the diseases, strep throat/ scarlet fever/rheumatic fever and post-streptococcal glomerulonephritis.
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List several components of the streptococcal cell wall that are antigenic.
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C carbohydrate- The C carb. was used by Rebecca Lancefield to divide streptococci into groups. Strep pyogenes has the lancefield group Atype of C carbohydrate.
M protein(80 types) This is a major virulence factor for the group A streptococcus. it inhibits the activation of complement and protects the organism from phagocytosis. It is also the weakest point in the organisms defense, because plasma (B) cells generate antibodies against the M protein. These antibodies bind to the M protein(opsonization) aiding in the destruction of the organism by macrophages and neutrophils. |
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Beta hemolytic group A strep. cocci have many enzymes that contribute to their pathogenicity. List several of them.
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Streptolysin O
Strep. S Pyrogenic exotoxin Streptokinase |
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What is Streptolysin O?
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The O is for oxygen labile as it is inactivated by O2. This enzyme destroys red and white blood cells and is the reason for the beta-hemolytic group A streptococci's beta hemolytic ability. Following pharyngeal or systemic infection with this group, antistreptolysin O(ASO) antibodies develop.
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What is streptolysin S?
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The S stands for oxygen stabile. This is also responsible for beta hemolysis, but is not antigenic.
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What is a pyrogenic exotoxin?
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It is also called erythrogenic exotoxin. This is found in only a few strains of beta-hemolytic group A streptococci. These starins can cause Scarlet fever.
Some strains produce pyrogenic exotoxins that are superantigens. The exotoxins directly superstimulate T cells to pour out inflammatory cytokines. This causes a streptococcal toxic shock syndrome. |
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List several components of the streptococcal cell wall that are antigenic.
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C carbohydrate- The C carb. was used by Rebecca Lancefield to divide streptococci into groups. Strep pyogenes has the lancefield group Atype of C carbohydrate.
M protein(80 types) This is a major virulence factor for the group A streptococcus. it inhibits the activation of complement and protects the organism from phagocytosis. It is also the weakest point in the organisms defense, because plasma (B) cells generate antibodies against the M protein. These antibodies bind to the M protein(opsonization) aiding in the destruction of the organism by macrophages and neutrophils. |
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Beta hemolytic group A strep. cocci have many enzymes that contribute to their pathogenicity. List several of them.
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Streptolysin O
Strep. S Pyrogenic exotoxin Streptokinase |
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What is Streptolysin O?
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The O is for oxygen labile as it is inactivated by O2. This enzyme destroys red and white blood cells and is the reason for the beta-hemolytic group A streptococci's beta hemolytic ability. Following pharyngeal or systemic infection with this group, antistreptolysin O(ASO) antibodies develop.
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What is streptolysin S?
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The S stands for oxygen stabile. This is also responsible for beta hemolysis, but is not antigenic.
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What is a pyrogenic exotoxin?
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It is also called erythrogenic exotoxin. This is found in only a few strains of beta-hemolytic group A streptococci. These starins can cause Scarlet fever.
Some strains produce pyrogenic exotoxins that are superantigens. The exotoxins directly superstimulate T cells to pour out inflammatory cytokines. This causes a streptococcal toxic shock syndrome. |
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What are some other enzymes produced by beta hemolytic group A streptococci?
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Streptokinase- activates the proteolytic enzyme, plasmin, which breaks up fibrin and blood clots.
Hyoluronidase DNAases Anti-C5a peptidase. |
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Beta hemolytic group A streptococci cause 4 types of diseases by local invasion and/or exotoxin release. List them.
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Strep pharyngitis
Streptococcal skin infections Scarlet fever Streptococcal toxic shock syndrome. |
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List 2 diseases that this same group can cause by delayed antibody mediated diseases.
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Rheumatic fever
Glomerulonephritis. |
