Transcript Cold sores
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.