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.
- 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.
- 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
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