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28 Cards in this Set
- Front
- Back
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Corynebacterium diphtheriae
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1. high G + C gram-positive bacteria
2. Related taxonomically related to streptomyces and mycobacteria 3. obligate aerobe 4. non-motile 5. non-encapsulated |
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bacillus anthracis
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spore-forming, poly-D-glu encapsulated, gram positive, rod-shaped; two virulence factors: 3-protein toxin and a capsule
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anthrax toxin (protective antigen)
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binds to cellular receptor and is then cleaved by a host protease which activates it; forms a pore-complex and EF/LF bind to it and get sucked into host cytosol which makes cells undergo apoptosis.
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lethal factor LF
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kills macrophages by inducing inflammasome and caspase-1 mediated cell death
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cholesterol-dependent cytolysins
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specific pore-former; binds to cholesterol (ex. streptolysin O)
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superantigens
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bind to MHC class 2 molecules and activate subsets of T-cells which release IL-2 and then indirectly, TNF; can activate as many as 1/5 T-cells
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streptococcus pneumoniae
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1. Gram-positive
2. diplococcus 3. low G + C 4. encapsulated with 80 serotypes 5. facultative anaerobe 6. non-motile 7. obligate parasites |
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Unique features of the gram-positive wall
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1. lack a periplasm
2. No outer membrane 3. no LPS 4. lipoproteins/surface proteins are anchored to peptidoglycan with LPXTG sequence near the C-terminus |
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S. pneumoniae virulence factors
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1. capsule - antiphagocytic
2. M-like proteins -adherence 3. penumolysin- member of the CDC family of pore forming hemolysins |
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staphylococcus aureus
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1. non-motile
2. facultative anaerobe 3. low G + C 4. gram-positive 5. grape-like clusters 6. can tolerate high salt |
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S. aureus virulence factors (determinants of pathogenesis)
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1. protein A: classic LPXTG protein (binds to Fc region of antibody IgG- can shield itself from host immunity and may prevent antibody specific to the bug from binding productively to the bug because protein A is in between)
2. 15 enzymes or enzyme activators |
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streptococcus pyogenes
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1. gram positive
2. fastidious 3. growth in chains 4. facultative anaerobes 5. low G + C |
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streptococcus pyogenes virulence factors
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1. capsule made of hyaluronic acid identical to the hyaluronic acid in CT. Antiphagocytic and therefore no antibodies to it.
2. M-proteins- surface exposed protein that is primary target of protective IgG |
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vibrio cholerae characteristics
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1. gram-negative
2. facultative anaerobe 3. comma-shaped 4. highly motile with single polar flagella sheathed with LPS 5. over 150 serotypes based on O-antigen but only two O1 and O139 cause disease 6. aquatic bacterium |
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cholera toxin structure
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AB toxin; two A subunits (A1 and A2 linked by disulfide linkages; ratio of B:A is 5:1; transcribed as an operon
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binding of cholera toxin
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CT binds via the B-subunits to the GM1 ganglioside
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cholera toxin mode of action
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CT catalyzes an ADP-ribosylation reaction; acts by transfer of ADP-ribose from intracellular NAD to the alpha chain of a trimeric G protein that functions to stimulate adenylate cyclase resulting in cAMP; prolonged levels of cAMP causes the high level of diarrhea
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What effects does v. cholerae have on immunity?
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cholera is a non-inflammatory disease and CT blocks inflammation. Promotes IL-10 production
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toxin co-regulated Pilus (TCP) role in virulence
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mediates attachment or mediates bacterium-bacterium interaction promoting biofilm formation
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toxR
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membrane spanning protein that is also a transcription factor that directly activates the CT promoter
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Bordetellae pertussis
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1. gram-negative
2. obligate aerobe 3. extracellular 4. |
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FHA and pertactin
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FHA: mediates adherence and target of antibody
Pertactin: also a surface protein that is a target of antibody |
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trachael cytotoxin (TCT)
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induces IL-1 by respiratory epithelial cells which in turn induces nitric oxide that has the toxic effect; potent effect upon neutrophils blocking chemotaxis and phagocytosis
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adenylate cyclase
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produces cAMP only in the presence of calmodulin; N-terminus is the adenylate cyclase, C-terminus is the pore-forming hemolysin (analogous to AB toxin); cyclase acts on phagocytic cells and renders them non-phagocytic
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Type III secretion
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newly discovered and present in both B. pertussis and B. bronchiseptica
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acellular pertussis vaccine
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purified mutated PT (non-toxic) mixed with FHA and pertactin
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Differences between bordetella bronchiseptica and pertussis
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B. bronchiseptica is motile at all temperatures; motility is needed for survival in environment
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Why are strains ectopically expressing flagella avirulent?
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1. TLR 5 trigged by flagellin (test with TLR 5 KO)
2. Nai S and Ipath -> activate inflammasome 3. generate antibodies to flagella -> opsonization and clears infection 4. slows down replication 5. type III secretion and flagellar systems are similiar |
