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Microbiology · Gram-positive rods

Clostridium tetani !

  • Bacterium
  • Gram-positive
  • Exam priority: high

A soil bacterium whose spores enter through wounds and make a toxin that causes severe muscle spasms; vaccination prevents it.

Updated 2026-11-01

Also called: tetanus bacillus

At a glance

Gram
Gram-positive
Shape
Rod with a terminal spore (drumstick)
Oxygen
Obligate anaerobe
Family
Clostridiaceae
Stain
Gram positive; spore former

Morphology

  • Slender Gram-positive rod
  • Round terminal spore that gives a drumstick shape
  • Spores resist heat and many antiseptics

Transmission

  • Spores from soil, dust, ash or animal faeces enter through wounds
  • Deep, puncture or soil-contaminated wounds
  • Umbilical cord cut with non-sterile tools (neonatal tetanus)
  • Not spread from person to person

Isolation precautions

What the care team adds to standard precautions.

  • Standard

Virulence factors

  • Tetanospasmin: travels up axons to the spinal cord
  • Cleaves synaptobrevin and stops GABA and glycine release from inhibitory interneurons
  • Result: sustained muscle contraction and spasms

Diseases it causes

  • Generalised, local, cephalic and neonatal tetanus Tetanus →

Clinical picture

  • Trismus (masseter spasm) as a frequent first sign
  • Risus sardonicus and neck stiffness
  • Opisthotonos and painful spasms set off by stimuli
  • Autonomic instability; consciousness preserved

Diagnosis

  • The diagnosis is clinical
  • Wound culture rarely helps and a negative culture does not rule it out

Treatment

Human tetanus immune globulin to neutralise free toxin, wound cleaning and debridement, an antibiotic (metronidazole), and spasm control with benzodiazepines plus ventilatory support in intensive care. Having tetanus gives no immunity: the patient is vaccinated on recovery.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • A complete tetanus toxoid series with boosters
  • Proper wound care
  • Tetanus immune globulin for high-risk wounds in people without a complete series
  • Clean delivery and hygienic umbilical cord care

Vaccine: Tetanus toxoid is in Colombia's PAI: pentavalent vaccine in infants, a DTP booster at five years, Td in adults and Tdap in every pregnancy to protect the newborn.

Test yourself

Think of the answer, then tap the question to see it.

What is the mechanism of tetanospasmin?

It cleaves synaptobrevin in spinal inhibitory interneurons and stops GABA and glycine release, so muscles stay contracted.

What is usually the first sign of tetanus?

Trismus, a spasm of the jaw muscles.

Why should a tetanus survivor be vaccinated?

Because the amount of toxin that causes disease is too small to induce protective immunity.

How is neonatal tetanus prevented?

By vaccinating the pregnant woman with tetanus toxoid and with clean delivery and hygienic cord care.

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← Back to the group: Gram-positive rods

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: About Tetanus (CDC, 2024); Tetanus (WHO, 2026); Tetanus: MedlinePlus Medical Encyclopedia (MedlinePlus (NLM), 2024); Informe de Evento 2023 Tétanos Neonatal (Instituto Nacional de Salud (INS), Colombia, 2024).

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Representative model, for educational purposes only.