Day 2.1 Micro Flashcards
What part of the bacteria stains with crystal violet?
Peptidoglycan layer.
Gram+ have big peptidoglycan layer, so they turn purple (violet)
What are the acute phase cytokines?
IL-1
IL-6
TNF-alpha
Where are Beta-lactamases located?
In the periplasm (space) of gram-neg bacteria. B-lactamases break down Abx like penicillin
What bacteria are encapsulated?
Some Killers Have Nice Shiny Bodies: Strep pneumonia Klebsiella Hemohilus influenza B Neisseria Salmonella B (gp B strep)
How do you test for encapsulated bacteria?
+ quelling reaction
Capsule swells with anti-capsular Ab.
(Doesn’t swell w/o Ab bc capsule protects)
The capsule serves an the Ag in which vaccines?
Pneumococcal (Pneumovax)
HiB
Meningiococcal
These vaccines are all derived from capsular Ag
What are the spore-forming bacteria
Only gram+ rods do this:
Bacillus (anthrax, B. cereus)
Clostridium (perfringens, tetani, botulinum)
Coxiella burnetti (Q fever)
Where is the DNA for Abx-resistance proteins (e.g. B-lactamase) found?
On plasmids. Not part of regular genome.
How does Endotoxin (lipid A) cause septic shock?
It activates macrophages, which release NO. NO causes vasodilation, which leads to hypotension and septic shock.
Where is endotoxin (LPS) found?
On the cell wall of gram-neg bactera, and in one gram+ bacteria: Listeria monocytogenes.
How does endotoxin (LPS) cause anaphylactic shock?
It activates the complement pathway, which causes C3a activation. C3a causes basophils and mast cells to degranulate and rls histamine, which causes vasodilation, hypotension, and edema.
What does C5a cause?
Neutrophil chemotaxis
Which are secreted, endotoxins or exotoxins?
Exotoxins are secreted. Endotoxin (LPS) is part of the cell wall.
Which needs a lower dose in order to be fatal, endo or exotoxin?
Exotoxin is the more fatal, meaning it needs only a small amt to be toxic. The toxicity of endotoxin is low, meaning it needs a higher dose to be toxic.
What are superantigens?
Exotoxins (secreted toxins)- bind directly to MHC-II and TCR simultaneously, activating lg numbers of Tcells to stimulate rls of IFN-gamma and IL-2.
S. aureus and S. pyogenes (gp A) have a lot of them.
What are the S. aureus superantigens (exotoxins)?
alpha-toxin - hemolysis
beta-toxin - sphingomyelinase
gamma-toxin (proteins A, B, C) - A + B = hemolysin (hemolysis), B + C = leukocidin (destroys leukocytes)
Enterotoxins A-E - food poisoning-vom/D
TSST-1 - rls cytokines - TSS
Epidermolytic/exfoliative - epithel cell lysis-scalded skin syndr
What are the Strep pyogenes (Gp A Strep) superantigens (exotoxins)?
Streptolysin O - hemolysis (O2 labile)
Streptolysin S - hemolysis (O2 stabile)
Erythrogenic /pyrogenic toxins - skin rash, fever of scarlet fever
What do ADP-ribosylating A-B toxins do?
Interfere w host cell fn
B (binding) part binds to a receptor on host cell surf, enabling endocytosis of the toxin.
A (active) part attaches and ADP-ribosyl to host cell protein (ADP ribosylation), altering protein fn
What are the pathogens with ADP ribosylating A-B toxins?
C. diptheriae
V. cholera
E.coli (ETEC)
B. pertussis
How does the ADP ribosylating toxin of Corynebacterium diptheria work?
Inactivates EF-2 (elongation factor), causes pharyngitis and pseudomembrane (gray) in throat. Don’t scrape or will get into blood and kill pt.
How does the ADP ribosylating A-B toxin of Vibrio cholera work?
ADP ribosylation of Gs protein stim’s adenylate cyclase, causes incrsd pumping of Cl- into gut and decrsd Na+ absorption. H20 follows salt in gut, causing voluminous rice-water diarrhea
How does the ADP ribosylating A-B toxin of ETEC work?
Heat-labile toxin stim’s adenylate cyclase
Heat-stabile toxin stim’s guanylate cyclase
both cause watery diarrhea
Labile like Air (A = adenylate)
Stabile like Ground (G = guanylate)
How does the ADP ribosylating A-B toxin of Bordetella pertussis work?
Increases cAMP by inhibiting Gi (Inhibits the inhibitor). Causes whooping cough. Inhibits chemokine receptor, causing lymphocytosis (increased lymphocytes)
When C. diptheria inactivates EF-2, this can interfere with protein synthesis in which cells?
Heart cells and nerve cells
What does the toxin of C. perfringens do?
alpha toxin- it’s a lecithinase that acts as a phospholipase to cleave cell membranes
causes gas gangrene
What does the toxin of C. tetani do?
Tetanospasmin
Blocks rls of inhibitory NTs GABA and Glycine.
Causes lockjaw
What drugs potentiate GABA?
Benzos and Barbituates.
GABA is the main inhibitory NT of the brain, so potentiating it means slowing down the brain.
What does the toxin of C. botulinum do?
Blocks rls of ACh, causing anti-cholinergic symptoms, CNA paralysis (esp cranial nerves) and floppy baby flaccid paralysis.
Spores in canned food and honey, don’t give to kids <1 yo
What does the toxin of B. anthracis do?
Includes edema factor, which is itself an adenylate cyclase- so it increases cAMP. (Without the Gprotein first)
What does the toxin of Shigella do?
Shiga toxin cleaves host cell rRNA, inactivating the 60S eukaryotic ribosome. Also enhances cytokine rls, causing HUS.
Shiga toxin is also md by E.coli
What does the toxin of S. pyogenes (Gp A Strep) do?
Streptolysin O- it’s a hemolysin.
It serves as the Ag for ASO Ab, which is used to dx rheumatic fever.
Also Streptolysin S and erythrogenic and pyrogenic toxins.
What toxins induce cAMP?
Vibrio cholera toxin (permanently activates Gs
Pertussis toxin (permanently inactivates Gi)
E. coli (ETEC) heat-labile toxin
B. anthracis (includes edema factor, which is an adenylate cyclase)
What causes scarlet fever? What are the toxins?
S. pyogenes (Gp A strep)- erythrogenic toxin (red skin) and pyrogenic toxin (fever)
What neurotransmitters does Tetanus toxin block?
GABA and Glycine (inhibitory NTs)