Lecture 25. Disease. Health. “ a state of complete physical, mental and social well being” …..World Health Organisation (WHO). Disease. Infectious or communicable diseases – diseases caused by other living organisms, they can be transmitted from one person to another.
“ a state of complete physical, mental and social well being” …..World Health Organisation (WHO)
“The successful invasion, establishment and growth of microorganisms in the tissues of the host”.
Developed in late 1800's , provide basic logical proof that disease is caused by a microbe
3. Avoid host defences.
4. Toxins – exotoxins and endotoxins.
Enters cell, inactivates elongation factor needed for protein synthesis.
Cell gradually loses ability to make proteins (same toxin molecule keeps inactivating more and more factors), shuts down.
2. Botulin toxin, a neurotoxin (attacks nervous system).
Clostridium botulinum, anerobic soil bacterium.
Most potent toxin known- 1 gram could kill 10 million people.
Toxin interferes with synaptic transmission at nerve-muscle junctions ---> flaccid paralysis.
Occurs most typically in improperly canned4. Exotoxins
3. Tetanus toxin, another neurotoxin.
Clostridium tetanus, anerobic soil bacterium.
Blocks synaptic transmission to inhibitory neurons, leads to rigid paralysis.
Common from deep wounds, pulled teeth.
Prevention: toxoid immunization (lasts 5-10 yrs).
4. Cholera toxin = an enterotoxin (attacks enteric tract).
Vibrio cholerae. is free-living in fresh water.
Binds to receptors on intestinal cells, chemically alters molecule involved in c-AMP production, leaves cAMP stuck in the "on" position.
Causes massive outflow of water (chasing outflow of Na+/Cl-). Similar mode of action for other enterotoxin.
Can be spread by drinking water, food (shellfish common).
Untreated, mortality is ~50%. With fluid replacement, <1%. Prevention: clean drinking water.4. Exotoxins
What organisms cause the following infections?
Give details of symptoms and how are the infections are