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Tetanus
Etiology
• Tetanospasmin neurotoxin produced by
Clostridium tetani
A-B type Exotoxin
B
B
A
Virulence factors
1. Portal of entry:
Parenteral rout. Microbe is an obligate
anerobe therefore the wound must be
deep enough to provide anaerobic
conditions.
Virulence factors
2. Attachment:
The glycocaylx and the structure of the wound
itself keeps the microbe in place. The microbe
produces Tetanospasmin, an exotoxin, that
targets neurons.
Tetanospasmin enters the nervous system at
neuromuscular junction. The B-chain of the toxin
binds to disialogangliosides (GD2 and GD1b) on
the neuron membrane.
Virulence factors
3.
Evade the Immune System
• The small amount of toxins required to cause
disease is so small that it doesn’t elicit an immune
response.
Virulence factors
• Tissue distruction:
• Tetanospasmin blocks neurotransmitters that cause muscles
to relax.
– The A-chain stops the affected neurons from releasing the
inhibitory neurotransmitters GABA (gamma-aminobutyric acid).
– The A-chain does this by degrading the protein synaptobrevin.
» Synaptobrevin is a protein found on membranes that allow
the fusion of vessicles with the plasma membrane and is
key for exocytosis. Vessicles carrying GABA are unable to
release the neurotransmiter by exocytosis.
– The consequence is dangerous over activity in the muscles
from the smallest stimulus.
• Short nerons are affected first such as those that innervate
the jaw.
• Death usually results when Respiratory muscles become
affected.
Transmission
• Indirect contact through a fomite.
– Enters body through a break in the skin. In
most cases, it spreads through a wound
contaminated by soil, dust or manure that
harbors the organism.
Reservoir
• Soil continated w/ animal fecal waste
• Tetanus is often associated with rust, especially
rusty nails, but this relationship is somewhat
misleading. Objects that accumulate rust are
often found outdoors, or in places that harbor
anaerobic bacteria, but the rust itself does not
cause tetanus nor does it contain more C. tetani
bacteria.
Signs and symptoms
• Tetany: which is spastic paralysis.
• Muscles of the jaw are affected early
(Lock-Jaw).
• Death results in respiratory failure.
Prophylaxis
• DTP Vaccination (Toxoid)
– 96% of 6 year olds have good immunity
– 30% of 70 year olds have good immunity
• Tetanus immune globulin (TIG) provides
temporary immediate immunity.
History
• Hundreds of thousands of cases of
tetanus occurred during the Civil War.