Clostridium tetani is a gram-positive rod-shaped bacterium that is found worldwide in soil; it is usually in its dormant form, spores, and becomes the rod-shaped bacterium when it multiplies. The vegetative rods produce the spore usually at one end of the rod (Figure 1). The organisms are considered anaerobic, meaning they do not require oxygen to survive.
- Clostridium tetani is the bacterium responsible for the disease. The bacteria are found in two forms: as a spore (dormant) or as a vegetative cell (active) that can multiply.
- The spores are in soil, dust, and animal waste and can survive there for many years. These spores are resistant to extremes of temperature.
- Contamination of a wound with tetanus spores is rather common. Tetanus, however, can only occur when the spores germinate and become active bacterial cells that release exotoxins.
- The active bacterial cells release two exotoxins, tetanolysin and tetanospasmin. The function of tetanolysin is unclear, but tetanospasmin is responsible for the disease.
- The disease typically follows an acute injury or trauma that results in a break in the skin. Most cases result from a puncture wound, laceration (cut), or an abrasion (scrape).
- Other tetanus-prone injuries include the following:
- Crush wound
- IV drug users (site of needle injection)
- Wounds with devitalized (dead) tissue (for example, burns or crush injuries) or foreign bodies (debris in them) are most at risk of developing tetanus.
- Tetanus may develop in people who are not immunized against it or in people who have failed to maintain adequate immunity with active booster doses of vaccine.
Figure 1: Picture of Clostridium tetani
, with spore formation (oval forms at end of rods). Source: CDC/Dr. Holdeman
Medically Reviewed by a Doctor on 8/6/2015
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