pathogenesis and toxigenicity part 1

are exotoxins that specifically target the intestinal mucosa.

• affect the camp levels
• result in increased elimination of water from intestinal cells
• cause voimiting and diarrhea

scac

• 1. superantigens
• 2. cytotoxins: type i-v
• 3. ab toxins
• 4. cytolytic toxins.

based on the secretion method that the bacteria uses to export the protein out of the cell.

the action on the toxin is within the cytoplasm

toxin is secreted directly into the cytosol in a contact-dependent manner

• Efficiency: poson enters only the target cell.
• selective: intracellular target is specific

• yes, membrane damaging and pore forming cytotoxins
•  
• yes, inhibit host cell protein synthesis and allow ca to escape from host cells

toxin is injected directly into the cytoplasm of the host cell

used by g- bacteria

• molecular syringes that resemble flagella (type 3)
• molecular syringes that resemble conjugative pili(type iv)

• Toxin enters without the aid of the bacteria 
• Active Binding

• A domain/ subunit- transferred across the plasma membrane into the host cell
• enters the cytoplasm and enzymatically acts on host targets.

• B domain/subunit- binds to cell surface receptors of host.
• helps to translocate the a domin/subunit.

yes, they are covalently joined but can be not joied

before entrance to host cell  and cleaved and activated by enzymes inside the host cell and at the plasma membrane of the host.

single ab protein- diptheria toxin

one a subunit + multiple b = cholera toxin

2 a + 1 b subunit= tripartite toxins or anthrax toxin

• Binary toxins
• before entry

corynebacterium diphtheria

a sub inhibits protein synthesis by the host cell by blocking the transfer of an amino acid from the trna to the polypeptide.

elongation factor 2 (ef2)

childhood disease and it affects the respiratory system.

group of seven related 1a + 1b subunits of ab toxins.

bind to pre-synatptic membranes of stimulatory motor neurons found at the neuromuscular junciton.

blocks the release of acetylcholine preventing muscles fro mreceiving an excitatory signal and therefore no contraction.

tetanospasmin

• motor neurons
• is transported to the spinal column and binds to ganglioside lipids of inhibitory neurons which produce glycine which stops release of acetylcholine which causes muscles to contract.