Overview of Genus Clostridium
- Gram-positive, spore-forming rods
- Strict anaerobes
- Found in soil, decaying vegetation, and the intestinal tract of animals/humans
- All Clostridium species produce exotoxins, many of which are neurotoxins or cytotoxins
General Characteristics
- Gram-positive bacilli with terminal round spores
- Characteristic “drumstick” appearance
- Motile — has peritrichous flagella
- Strict anaerobe
- Found in soil, dust, animal feces, and contaminated objects like cotton, wool, and surgical instruments
- Spores are extremely resistant and survive in harsh environments
Virulence Factors
- Tetanospasmin is antigenic and can be neutralized by antitoxin.
- All serotypes produce the same toxin, though they differ in surface antigens.
Pathogenesis of Tetanus
- 1. Spores enter via wound (deep puncture wounds, unsterile instruments, umbilical stump, injections, etc.)
- 2. Anaerobic conditions allow spores to germinate
- 3. Vegetative bacteria release tetanospasmin
- 4. Toxin binds to motor nerve endings, travels retrograde to CNS
- 5. Inhibits release of GABA & glycine → uncontrolled muscle contraction
- 6. Results in spastic paralysis, starting with lockjaw (trismus)
No tissue invasion or inflammation by the bacteria; disease is entirely toxin-mediated.