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23 Cards in this Set

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What is septic shock?
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.
What is tumor necrosis factor?
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.
Does TNF trigger the release of other substances?
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.
What is catalase, and what bacteria possess it?
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.
What else does catalase do and how can one test for it?
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.
How are Strep. species classified?
Certain species of streptococci can either completely or partially hemolyze RBC. Three groups are recognized;
Beta hemolytic
Alpha hemolytic
Gamma non-hemolytic.
Define each of these classifications.
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.
What are Lancefield antigens?
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.
Are all of these antigen groups significant?
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.
What is meant by Group A Beta- Hemolytic Streptococci?
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.
List several components of the streptococcal cell wall that are antigenic.
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.
Beta hemolytic group A strep. cocci have many enzymes that contribute to their pathogenicity. List several of them.
Streptolysin O
Strep. S
Pyrogenic exotoxin
Streptokinase
What is Streptolysin O?
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.
What is streptolysin S?
The S stands for oxygen stabile. This is also responsible for beta hemolysis, but is not antigenic.
What is a pyrogenic exotoxin?
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.
List several components of the streptococcal cell wall that are antigenic.
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.
Beta hemolytic group A strep. cocci have many enzymes that contribute to their pathogenicity. List several of them.
Streptolysin O
Strep. S
Pyrogenic exotoxin
Streptokinase
What is Streptolysin O?
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.
What is streptolysin S?
The S stands for oxygen stabile. This is also responsible for beta hemolysis, but is not antigenic.
What is a pyrogenic exotoxin?
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.
What are some other enzymes produced by beta hemolytic group A streptococci?
Streptokinase- activates the proteolytic enzyme, plasmin, which breaks up fibrin and blood clots.
Hyoluronidase
DNAases
Anti-C5a peptidase.
Beta hemolytic group A streptococci cause 4 types of diseases by local invasion and/or exotoxin release. List them.
Strep pharyngitis
Streptococcal skin infections
Scarlet fever
Streptococcal toxic shock syndrome.
List 2 diseases that this same group can cause by delayed antibody mediated diseases.
Rheumatic fever
Glomerulonephritis.