Clostridium tetani

Categorization
Cell Wall: Gram Positive Metabolism: Obligate Anaerobe
Shape: Spore-forming Rod. A single, terminal spore is present at the end of each rod, giving a "Tennis Racket" like appearance
Transmission
  • C. tetani spores are common in the soil and may exist on sharp objects on the ground like rusty nails. Spores are introduced via puncture wounds and germinate in the anaerobic necrotic environment, subsequently elaborating tetanus exotoxin.
Virulence Factors
  • Tetanus Toxin
    • Tetanus exotoxin is absorbed at the neuromuscular junction and directs its retrograde transport up the peripheral nerve's axon to the cell body in the spinal cord. Remarkably, it then crosses the synapse and enters the presynaptic neuron terminal and inhibits release of inhibitory neurotransmitters such as GABA and Glycine. Consequently, spasm of innervated muscles occurs.
Clinical Consequences
  • Tetanus is characterized by increases in muscle tone and paroxysmal muscle spasms. The following muscle groups are typically affected
    • Masseter Muscle: Resulting in "Lock Jaw".
    • Muscles of the Face: Resulting in the characteristic sneer termed "Risus Sardonicus"
    • Muscles of Swallowing: Resulting in dysphagia
    • Muscles of Breathing: Can compromise capacity to breath and may result in fatality
Vaccine
  • DPT vaccine: One component of this vaccine (DPT) is the inactivated, formalin-fixed Tetanus Toxin which results in humoral immunity and thus inactivating antibodies to the toxin.
Treatment
  • Immunization is usually performed on all individuals regardless of symptomology or previous immunization status. Antitoxin therapy composed of an antibody which binds and neutralizes the toxin is given to those who have not been immunized or whose immunizations occurred more than a decade ago. Antibiotics are of unclear value but natural penicillin is usually administered to symptomatic patients. Muscle relaxants and respiratory support are administered as needed to clearly symptomatic individuals.