Term
| What is the difference between endotoxins and exotoxins? |
|
Definition
-Endotoxins are *LPSs, not proteins, and are secreted until death of the bacteria
-Exotoxins are actively secreted *proteins
-The proteins tend to be directly toxic while LPS's toxicity lies in its ability to overstimulate the immune system |
|
|
Term
| In what cells do we see endotoxins? What is the actual toxic portion? Can we make it into a toxoid for vaccination? What makes it toxic? |
|
Definition
-Endotoxin is basically another name for LPS, which we see in gram- bacteria only
-The toxic portion is lipid A which is not released until death (except in the case of N. meningitidis
-LPS is heat stable (how we convert it) and strongly immunogenic, so we cannot make it into a toxoid
-It is toxic because it over-activates **macrophages leading to secretion of many cytokines and stimulating bradykinin(-->vasodilation & shock) and Hageman factor(-->DIC) over-activation
-Reminder; Hageman factor (AKA F12) is at the top of the endogenous pathway of the coagulation cascade |
|
|
Term
|
Definition
-It is another structural protein (like LPS) that acts as a toxin
-Similar, but less severe, than LPS, but from gram+ cells
-However, not considered an endotoxin! |
|
|
Term
| What cells secrete exotoxins? Can we make them into toxoids? Give the two examples of exotoxins? |
|
Definition
-Gram+ bac (and some gram-) produce these proteins
-We can make them into toxoids for vaccination
A-B component toxins;
-B component Binds allowing internalization
-A component is Active (toxic)
-Can be enterotoxins, neurotoxins, or cytotoxins
Cytolysins; lyse cells
-C. perfringens alpha toxin & Staphlococcus aureus alpha toxin are both examples |
|
|
Term
| What are four examples of protein synthesis inhibiting exotoxins? Give organism, toxin, and mode of action? |
|
Definition
-There are two main mechanisms employed
ADP Ribosylation of EF-2 (elongation factor 2);
-Diphtheria toxin from Corynebacterium diphtheriae (+)
-Exotoxin A from Pseudomonas aeruginosa (-)
Interference with 60S ribosomal subunit;
-Shiga toxin from Shigella dysenteriae (-) (causes bloody diarrhea)
-Verotoxin from Enterohemorrhagic E. coli (-) (same) |
|
|
Term
| Give the two neurotoxin examples of exotoxins? What kind of paralysis do they present with? Mode of action? |
|
Definition
-Tetanus toxin from Clostridium tetani (+) causes a spastic type of paralysis (arched back etc.)
-Works by blocking inhibitory transmitters glycine and GABA
-Botulinum toxin from Clostridium botulinum (+) causes flaccid type paralysis
-Works by blocking release of acetylcholine at cholinergic synapses
-This is the active ingredient in BOTOX
-Notice that both are from the same genus (I think lol) |
|
|
Term
| Give the two super-antigen examples of exotoxins? When do they result in? |
|
Definition
-TSST-1 from Staphylococcus aureus (+)
-Exotoxin A from Streptococcus pyogenes (+) (note; diff than one from pseudomonas)
-Both have their effect by overstimulating the immune system and causing toxic shock (toxic shock synd. toxin) |
|
|
Term
| Go through the cAMP inducing exotoxins (4) and mode of action? |
|
Definition
1. Heat labile toxin (LT) from Enterotoxigenic e. Coli (-)
-ADP ribosylation and *stimulation of Gs protein
2. Cholera toxin from Bibrio cholerae (-)
-Same as E. coli LT (both causing profuse diarrhea)
3. Anthrax toxin from Bacillus anthracis (+)
-Actually a mix of three proteins, two of which are toxins
-EF (edema factor) and LF (lethal factor) are the toxins (causing edema and cell death, respectively)
-PA (protective antigen) is the B component (binding) for both of the toxins above
4. Pertussis toxin from Bordetella pertussis (-)
-ADP ribosylation and *inhibition of Gi protein |
|
|
Term
| What are the two cytolysin exotoxins? |
|
Definition
-Both are Alpha toxins
-One is from Clostridium perfringens (+) and the other from Staph. aureus
-Note, however, that staph aureus also has TSST-1 which is much more important to its virulence
Both form puncture membrane;
-CP's alpha toxin is a *lecithinase (a phospholipase)
-SA's intercalates to form a pore
-Neither are really that potent of exotoxins |
|
|
Term
| As a review, what antibiotics act on the ribosome? |
|
Definition
-Chloramphenicol (blocks pep bond)
-Erythromyosin (blocks translocation)
-Tetracycline (blocks incoming AAs)
-Aminoglycosides (e.g. kanamysin and stroptomysin) (blocks fMet and causes misreading)
-The protein inhibiting exotoxins do the same sort of things, but to eukaryotic cells |
|
|
