bacterial toxins Flashcards
1
Q
steps required of a bacterium to cause disease
A
- encounter/enter host
- establish an infectious niche
- multiply, cause tissue damage
- spread to other tissues, or other hosts, or both
2
Q
factors responsible for pathogenicity
A
- colonization factors
- survival factors
- factors that cuase damage or spread
- regulatory factors
3
Q
toxins
A
- directly damage the host in specific way
- purpose is to obtain cell associated nutrients, facilitate dissemination, and interfere with host defenses
4
Q
-toxin:
A
protein that damages eukaryotic cells
5
Q
exotoxin vs endotoxin
A
- exotoxin: most classical toxins
- endotoxin: non-proteinaceous lipopolysaccharide of gram neg bacteria
6
Q
classification of toxins
A
- exotoxins named on the basis of their target
- can classify based on their site of action: target on cell surface, target in cytosol
7
Q
What questions can you ask when determining the role of a toxin
A
- toxigenic illnesses were -among the first to be studied
- investigators can ask: does purified toxin mimic the illnes? do Abs that recognize the toxin decrease the illness? phenotype or specific tox- bacteria
8
Q
C difficile toxins (gene comp)
A
- enzymatically active domain
- cystein protease domain
- hydrophobic region
- receptor binding carbohydrates
9
Q
botulism
A
- clostridium botilinum
- obligate anaerobic
- gram +
- spore forming
- toxin causes flaccid paralysis
- rare
- intoxication rather than a true infection
- Abs can alleviate
10
Q
mechanism of botulism toxin
A
- A and B toxins
- A: enzymatically active domain translocated by the B domain. is a protease that prevents Ach release . Cleaves proteins involved in synaptic vescle fusion
- B: cell binding domain recognizes target cell. receptor mediated endocytosis . acidification results in membrane insertion
11
Q
targets of botulism
- A,E
- C
- B,D,F,G
A
- A,E: SNAP-25
- C: syntaxin
- D: synaptobrevin
12
Q
tetanus
A
- c tetani
- spore forming obligate anaerobe
- gram+
- bacillus
- spores enter a wound, germinate, and produce toxin
- similar to the botulism neurotoxin
- poisons neurotransmitters released by cleavage of proteins involved in vesicle fusion
- tetanus toxin causes spastci (not flaccid) paralysis
13
Q
flaccid vs spastic paralysis
A
- conferred by cell binding specificity of the B subunits
- tetanus is translocated to the CNS and prevents the release of NTs such as GABA
- botulism toxins are translocated to the peripheral nerves and prevents the release of stimulatory NTs such as Ach so muscle can not be stimulated to contract
14
Q
cholera
A
- large volume of watery diarrhea
- vibrio cholerae is a gram -, comma shaped, facultative anaerobe
- noninvasive: all important symptoms are due to action of a single toxin
- acquired by ingestion of contaminated water or food
- small intestine is the site of damage induced by toxin
- generates alkaline pH, which inhibits competing bacteria
- cholera toxin inducesprofuse watery rice water diarrhea
- mild to severe cases
- can result in extreme dehyrdration and hypotension
- can be rapidly fatal
15
Q
how is the balance of water controlled in the intestine
A
-ion flux
