Clostridium tetani

Question 1

General features and habitat of Clostridium tetani

Answer 1

Gram +
Rod shape
Reservoir- soil and rusty nails

Question 2

Biochemical Properties of Clostridium tetani

Answer 2

Obligate anaerobe (to distinguish from Bacillus species)
Spore forming

Question 3

Pathogenesis of Clostridium tetani

Answer 3

Transmitted by puncture wound (trauma) from rusty nails or human bites

Puncture wound with foreign object, which contains C. tetani spores

Spores are embedded in the flesh and germinate

Tetanospasmin toxin (AB type neurotoxin) is released and travels through
motor axons to the spinal cord (retrograde axonal transport)

The toxin cleaves SNARE proteins, causes Inhibition of exocytosis of
neurotransmitters into NMJ (synapse)

SNARE cleavage leads to inhibition of the release of GABA and Glycine
(inhibitors of muscle contraction) causes uncontrolled muscle contractions
GABA and Glycine are released by Renshaw cells (but they are inhibited)

Question 4

Clinical Features (Tetanus) of Clostridium tetani

Answer 4

Spastic paralysis- continuous muscle spasms (contractions)

Risus sardonicus (“evil grin”, also known as Lock-Jaw symptom)- tense muscle spasm prevent the jaws from opening

Opisthotonus- exaggerated arching of the back due to back muscles spasm

Complications- involvement of the autonomic system may cause cardiac arrhythmias

Question 5

Diagnosis of Clostridium tetani

Answer 5

Primarily a clinical diagnosis- organism is rarely isolated (not useful to cultivate)

Question 6

Treatment of Clostridium tetani

Answer 6

Passive immunization- anti-toxin (Human Tetanus Immunoglobulin, TETIG)
Can also give DTP if not vaccinated (if vaccinated > 10 years)

Question 7

Prevention of Clostridium tetani

Answer 7

DTP Toxoid vaccine- contains inactive tetanus toxin (i.e. toxoid)