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28 Cards in this Set

  • Front
  • Back
Corynebacterium diphtheriae
1. high G + C gram-positive bacteria
2. Related taxonomically related to streptomyces and mycobacteria
3. obligate aerobe
4. non-motile
5. non-encapsulated
bacillus anthracis
spore-forming, poly-D-glu encapsulated, gram positive, rod-shaped; two virulence factors: 3-protein toxin and a capsule
anthrax toxin (protective antigen)
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.
lethal factor LF
kills macrophages by inducing inflammasome and caspase-1 mediated cell death
cholesterol-dependent cytolysins
specific pore-former; binds to cholesterol (ex. streptolysin O)
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
streptococcus pneumoniae
1. Gram-positive
2. diplococcus
3. low G + C
4. encapsulated with 80 serotypes
5. facultative anaerobe
6. non-motile
7. obligate parasites
Unique features of the gram-positive wall
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
S. pneumoniae virulence factors
1. capsule - antiphagocytic
2. M-like proteins -adherence
3. penumolysin- member of the CDC family of pore forming hemolysins
staphylococcus aureus
1. non-motile
2. facultative anaerobe
3. low G + C
4. gram-positive
5. grape-like clusters
6. can tolerate high salt
S. aureus virulence factors (determinants of pathogenesis)
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
streptococcus pyogenes
1. gram positive
2. fastidious
3. growth in chains
4. facultative anaerobes
5. low G + C
streptococcus pyogenes virulence factors
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
vibrio cholerae characteristics
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
cholera toxin structure
AB toxin; two A subunits (A1 and A2 linked by disulfide linkages; ratio of B:A is 5:1; transcribed as an operon
binding of cholera toxin
CT binds via the B-subunits to the GM1 ganglioside
cholera toxin mode of action
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
What effects does v. cholerae have on immunity?
cholera is a non-inflammatory disease and CT blocks inflammation. Promotes IL-10 production
toxin co-regulated Pilus (TCP) role in virulence
mediates attachment or mediates bacterium-bacterium interaction promoting biofilm formation
membrane spanning protein that is also a transcription factor that directly activates the CT promoter
Bordetellae pertussis
1. gram-negative
2. obligate aerobe
3. extracellular
FHA and pertactin
FHA: mediates adherence and target of antibody
Pertactin: also a surface protein that is a target of antibody
trachael cytotoxin (TCT)
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
adenylate cyclase
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
Type III secretion
newly discovered and present in both B. pertussis and B. bronchiseptica
acellular pertussis vaccine
purified mutated PT (non-toxic) mixed with FHA and pertactin
Differences between bordetella bronchiseptica and pertussis
B. bronchiseptica is motile at all temperatures; motility is needed for survival in environment
Why are strains ectopically expressing flagella avirulent?
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