15.1.1.2.3: Clostridium tetani
Organism
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Clostridium tetani is a moderately-sized Gram-positive , endospore-producing bacillus.
- Motile with a peritrichous arrangement of flagella.
- Produce round, terminal endospores that give the bacterium a "tennis-racquet" appearance.
- An obligate anaerobe (def) .
Habitat
- Colonizes the intestinal tract in humans and animals.
Source
- Endospores found in fertile soil or feces.
Epidemiology
- Endospores are found in most soils and in the intestinal tract of many animals and humans.
- Although exposure to endospores is commom, disease is uncommon except in countries with poor medical care and vaccination compliance.
- Fewer than 50 cases per year in the U.S.; most in elderly individuals with waning immunity.
- It is estimated that there is more than one million cases a year worldwide, with a mortality rate of 20% to 50%.
- Most deaths occur in neonates and originates from infection of umbilical stumps in mothers that have no immunity.
Clinical Disease
- Generalized tetanus is most common. Typical presenting symptoms include lockjaw and sardonic smile, arrising as a result of spastic paralysis of the masseter muscles and other facial muscles. Difficulty in swallowing, drooling, irritability, and persistent back spasms are other early symptoms. When the autonomic nervous system is involved, symptoms include perfuse sweating, hyperthermia , cardiac arrhythmias , and fluctuations in blood pressure.
- Cephalic infection primarily infects the head and involves cranial nerves.
- Localized infection involves the muscles in the area of primary injury.
- Neonatal tetanus is in newborns and originates from infection of umbilical stumps in mothers that have no immunity.
- The infection begins when endospores of C. tetani enter an anaerobic wound . Since the bacterium is an obligate anaerobe, an anaerobic environment is needed for the endospores to germinate and the vegetative bacteria to grow. Vegetative bacteria eventually produce tetanospasmin, the toxin responsible for symptoms of tetanus.
Primary Virulence Factors
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Tetanospasmin
- AB exotoxin (neurotoxin)
- Inhibits release of glycine and gamma-amino butyric acid (GABA) from inhibitory motor neurons. As a result, muscular contractions are uncontrolled.
** CDC Recommendations for tetanus prophylaxis.
From Tetanus, by Daniel J Dire, MD, FACEP, FAAEM, Associate Professor, Department of Emergency Medicine, University of Alabama at Birmingham and Daniel J Dire, MD, FACEP, FAAEM, is a member of the following medical societies: American Academy of Clinical Toxicology, American Academy of Emergency Medicine, Association of Military Surgeons of the US, and Society for Academic Emergency Medicine