Tetanus Practice Questions

Correct answer: Clostridium tetani

Clostridium tetani is the specific anaerobic, Gram-positive, spore-forming bacterium responsible for tetanus. While other Clostridium species cause diseases like botulism or gas gangrene, only C. tetani produces the tetanospasmin toxin.

Correct answer: Terminal spores giving a drumstick appearance

C. tetani produces spherical terminal spores that are wider than the vegetative cell, creating a characteristic 'drumstick' or 'tennis racket' appearance under the microscope. This morphological feature is a key diagnostic identifier in microbiology.

Correct answer: Neurotoxin

Tetanospasmin is a potent neurotoxin that specifically targets the nervous system. It blocks the release of inhibitory neurotransmitters, leading to the characteristic muscle spasms of the disease.

Correct answer: Cleavage of SNARE proteins to prevent neurotransmitter release

Tetanospasmin is a zinc metalloprotease that cleaves synaptobrevin, a SNARE protein required for vesicle docking. By destroying this protein, the toxin prevents the release of inhibitory GABA and glycine into the synaptic cleft.

Correct answer: GABA and Glycine

The toxin prevents the release of Gamma-aminobutyric acid (GABA) and glycine, which are the body's primary inhibitory neurotransmitters. Without these, lower motor neurons become hyperactive, causing tetanic muscle contractions.

Correct answer: Facial muscles

Risus sardonicus, or the 'sardonic grin,' is caused by the involuntary contraction of the masseter and facial muscles. It is a classic early clinical sign of generalized tetanus.

Correct answer: Via retrograde axonal transport in motor neurons

The toxin is taken up by the nerve terminals of lower motor neurons and moves toward the spinal cord and brainstem via retrograde axonal transport. Once in the CNS, it migrates transsynaptically into inhibitory interneurons.

Correct answer: 3 to 21 days

The incubation period for tetanus typically ranges from 3 to 21 days, with an average of about 8 days. Generally, a shorter incubation period is associated with more severe disease and a higher risk of mortality.

Correct answer: Infection of the umbilical cord stump

Neonatal tetanus usually occurs through infection of the unhealed umbilical cord stump, often when non-sterile instruments are used for cutting or when contaminated dressings are applied. It is a significant cause of infant mortality in areas with poor birthing hygiene.

Correct answer: Low oxygen tension (anaerobic)

C. tetani is an obligate anaerobe, meaning spores will only germinate and produce toxin in environments lacking oxygen. Necrotic tissue or deep puncture wounds provide the ideal anaerobic conditions for this process.

Correct answer: Localized tetanus

Localized tetanus involves persistent muscle contractions in the same anatomic area as the injury. While it can be a precursor to generalized tetanus, it often remains a milder, localized form in partially immune individuals.

Correct answer: Head trauma or otitis media

Cephalic tetanus is a rare form of the disease associated with head wounds or otitis media (chronic ear infections). It frequently involves cranial nerve palsies, particularly the seventh cranial nerve (facial nerve).

Correct answer: To neutralize unbound toxin in the bloodstream

TIG provides passive immunity by neutralizing circulating tetanospasmin that has not yet bound to nerve endings. It cannot reverse the effects of toxin that is already fixed to the nervous system, which is why supportive care is also required.

Correct answer: Inactivated tetanus toxin

The vaccine is a toxoid, which is the tetanus toxin that has been modified (usually by formaldehyde) to remain antigenic while losing its toxicity. It stimulates the body to produce protective antibodies against the toxin.

Correct answer: Metronidazole

While Penicillin G was traditionally used, Metronidazole is now preferred because it has better penetration into anaerobic tissues and does not potentially antagonize GABA receptors like penicillin might.

Correct answer: Labile blood pressure and tachycardia

Advanced tetanus can cause autonomic nervous system dysfunction, leading to 'autonomic storms.' These are characterized by unpredictable fluctuations in heart rate (tachycardia) and blood pressure (hypertension/hypotension), as well as sweating and fever.

Correct answer: The lethal dose of toxin is insufficient to trigger immunity

Tetanospasmin is extremely lethal at very low concentrations. A dose sufficient to cause clinical disease is actually below the threshold required to stimulate a protective immune response, so natural infection does not confer immunity.

Correct answer: Every 10 years

Antibody levels against tetanus toxin decline over time. To maintain protective levels of antitoxin, a booster dose (Td or Tdap) is recommended every 10 years for all adults.

Correct answer: Clinical presentation and history

The diagnosis of tetanus is almost entirely clinical, based on the history of an injury and the presence of characteristic symptoms like muscle rigidity and spasms. Laboratory tests and cultures are often negative and are not required for diagnosis.

Correct answer: Involuntary arching of the back

Opisthotonos is a state of severe hyperextension and spasticity in which the patient's head, neck, and spinal column enter a complete 'bridging' or arching position. It results from the powerful contraction of the extensor muscles of the back.