Clostridium tetani

Background

• Ubiquitous soil organism
• Acquired either by direct inoculation or via umbilical stump in neonates

Microbiology

• Thin Gram-positive bacillus, with terminal spore (drumstick appearance), with numerous spores

Pathophysiology

• The toxin, tetanospasmin, is a zinc-dependent matrix metalloproteinase that blocks inhibitory interneurons in the spinal cord and autonomic nervous system

Epidemiology

• Rare in developed countries (0.1 to 0.2 cases per million people in the US)
• Cases and deaths have decreased substantially after introduction of vaccination

Clinical Manifestations

• Incubation period of 3 to 21 days, which is followed by a period of onset to the first generalized spasm
  • Shorter incubation period and period of onset are both associated with poorer prognosis

Generalized Tetanus

• Disease is characterized by tonic spasms
• Classically starts with muscles of the jaw, causing trismus, lockjaw, and risus sardonicus, and sometimes abdominal rigidity
• Progresses to generalized spasm, which involves decorticate posturing with opisthotonus, arm flexion, and leg extension
  • Spasms may be triggered by sensory stimuli
  • May cause airway obstruction, and may involve diaphragm, both of which can be fatal
• Disease progresses over two weeks, with complete recovery taking another month

Localized Tetanus

• Rigidity of muscles near the site of inoculation
• May be mild and often resolves spontaneously over time
• May progress to generalized tetanus

Cephalic Tetanus

• Localized tetanus involving the cranial nerves following a head injury

Neonatal Tetanus

• Caused by infection of the umbilical stump, due to contamination in the context of unimmunized mothers
• Presents with generalized weakness and failure to nurse, followed eventually by rigidity and spasms
• Very high mortality (90%)

Prognosis and Complications

• 30% mortality
• Can cause bony fractures, asphyxia, hematomas, and rhabdomyolysis

Diagnosis

• Almost entirely a clinical diagnosis, due to low yield of organism and toxin from clinical samples
• Baseline IgG serology; if positive, then they are tetanus-immune and it rules out the diagnosis
• Send wound swab or tissue for culture or PCR

Management

• Supportive care
  • Early intubation for airway protection
  • Benzodiazepines to manage muscle spasms
    • Rarely, need to escalate to neuromuscular blockage
  • May need α- or β-adrenergic blockade with labetalol to manage autonomic dysfunction
    • Avoid unopposed α effect, which can cause severe hypertension
  • Increased nutritional support, given the high metabolic demands of the illness
• Immunization
  • Tetanus antitoxin, tetanus immune globulin (TIg), or IVIg can shorten the duration of illness. Administer as early as possible and within 24 hours.
  • Vaccination with toxoid vaccine, within 24 hours, into a different limb.
• Metronidazole may improve outcomes compared to penicillin
• Wound care with debridement as indicated, though it does not alter the course of the disease

Prevention

Vaccination

• The tetanus toxoid vaccine is part of the routine childhood immunization

Postexposure Prophylaxis

• Postexposure prophylaxis involves either tetanus vaccination, tetanus immunoglobulin (TIg), or both

Immunization Status	Wound	Vaccine	Immunoglobulin
did not complete childhood series, or unknown	clean, minor injury	yes	no
	all others	yes	yes
completed childhood series	clean, minor injury	only if last was given ≥10 years ago	no
	all others	only if last was given ≥5 years ago	no