Clostridia are gram-positive, obligate anaerobic bacilli.
C. tetani produces an exotoxin called tetanospasmin, that prevents the release of glycine from inhibitory neurons (Renshaw cells) in the spinal cord causing a spastic paralysis.
When tetanospasmin enters a neuron at the neuromuscular junction, it travels in a retrograde direction via the motor protein dynein to reach the central nervous system.
Once in the central nervous system, tetanospasmin cleaves a SNARE protein (soluble NSF attachment), synaptobrevin 2, thus preventing the fusion of the membrane vesicles and inhibiting the release of GABA and glycine from the inhibitory cells. Therefore, the excitatory neurons are not countered by the inhibitory neurons resulting in a hyperactivity of the muscles when stimulated and leading to tetanic spasms.
The tetanus vaccine is a cell-free purified toxin that is normally given as part of a combined vaccine.
Tetanus vaccine is currently given in the UK as part of the routine immunisation schedule at:
This, therefore, provides 5 doses of tetanus-containing vaccine. Five doses is now considered to provide adequate long-term protection against tetanus.
The Greenbook contains the full criteria. The information below is only an abbreviated summary:
The first step is to classify the wound:
| Clean wound | Tetanus prone wound | High-risk tetanus prone wound |
|---|---|---|
| Wounds less than 6 hours old, non-penetrating with negligible tissue damage | • puncture-type injuries acquired in a contaminated environment e.g. gardening injuries | |
| • wounds containing foreign bodies | ||
| • compound fractures | ||
| • wounds or burns with systemic sepsis | ||
| • certain animal bites and scratches | • heavy contamination with material likely to contain tetanus spores e.g. soil, manure | |
| • wounds or burns that show extensive devitalised tissue | ||
| • wounds or burns that require surgical intervention |
Patient has had a full course of tetanus vaccines, with the last dose < 10 years ago