37. Anaerobic spore-forming bacteria – genus Clostridium. General characteristics. Clostridium tetani. Morphology, biology and toxin production. Pathogenecity and immunity. Microbiological diagnosis. Specific prophylaxis and therapy. The causative agents of gas gangrene. Morphology, biology and toxin production. Pathogenecity, disease and immunity. Microbiological diagnosis. Prophylaxis and therapy. Clostridium botulinum. Morphology, biology and toxin production. Pathogenesis and immunity. Microbiological diagnosis. Prophylaxis and therapy.

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.