Tetanus Flashcards
Clostridium tetani
Clostridium tetani is an obligate anaerobic, gram-positive bacillus with terminal round spore (drum stick appearance).
It is ubiquitous in nature, widely distributed in soil, hospital environment and in the intestine of man and animals.
Virulence factors of tetanus
1. Tetanolysin: hemolysin no role in pathogenesis 2. Tetanospasmin (or tetanus toxin): • neurotoxin responsible for disease • antigenic and is specifically neutralized by its antitoxin • plasmid coded Toxoid: It gets toxoided spontaneously or by formaldehyde(antigenic, but not virulent) ➡️ used for vaccine preparation
Mechanism of Action of Tetanus Toxin
- Tetanus toxin binds to receptors (polysialogangliosides) present on motor nerve terminals
- Toxin internalization.
3. Transported in retrograde way to the GABA and glycine
4. It prevents the presynaptic release of inhibitory neurotransmitters - Spastic muscle contraction.
Tetanus
mode of transmission
- Injury (superficial abrasions, punctured wounds,…)
2. Surgery done without proper asepsis
3. Neonates:
Following abortion/delivery, due to unhygienic practices
4. Otitis media (otogenic tetanus)
It is non-infectious: No person-to-person spread
Tetanus
clinical manifestations
- First symptom: 🔼 masseter tone ➡️ lockjaw
- Muscle pain and stiffness, back pain, and dysphagia
📝 Difficulty in feeding is the initial presentation in 👶 - Painful muscle spasm develops which may be:
• Localized: Involves the affected limb
• Generalized painful muscle spasm ➡️ descending spastic paralysis (except 💪,🦵). Deep tendon reflexes exaggerated
4. Autonomic disturbance is maximal during the 2nd week:
🔽 or 🔼 bp, tachycardia, intestinal stasis, sweating, 🔼 tracheal secretions and acute renal failure.
Tetanus
complication
- Risus sardonicus:
abnormal, sustained spasm of the facial muscles that appears to produce grinning - Opisthotonos position:
due to generalized spastic contraction of the extensor muscles
3. Respiratory muscles spasm:
airway obstruction
Tetanus is more common in developing countries including India, which is attributed various risk factors such as
- Warm climate
- Rural area with fertile soil
- Unhygienic surgeries or deliveries.
Tetanus lab diagnosis
specimen and methods
Specimen:
Excised tissue bits from the necrotic depths of wounds are more reliable than wound swabs.
1. Gram staining:
gram-positive bacilli with terminal and round spores (drum stick appearance)
2. Culture: more reliable
3. Toxigenicity test:
In vivo mouse 🐁 inoculation
Tetanus
gram staining as lab diagnosis
- Gram staining reveals gram-positive bacilli with terminal and round spores (drum stick appearance)
- However, microscopy alone is unreliable as it cannot distinguish C. tetani from morphologically similar non-pathogenic clostridia like C. tetanomorphum and C. sphenoides.
Tetanus
culture as lab diagnosis
Culture is more reliable than microscopy.
1. Robertson cooked meat broth:
C. tetani, being proteolytic turns the meat particles black and produces foul odor
2. Blood agar with polymyxin B:
The plates are incubated at 37°C for 24–48 hours under anaerobic condition.
C. tetani produces characteristic swarming growth
Toxigenicity test for tetanus lab diagnosis
As pathogenesis of tetanus is toxin mediated, the association of the isolated organism can only be established when its toxin production is demonstrated.
Toxin assay can be performed by in vivo mouse inoculation test on specimens such as serum and urine
Treatment of tetanus
- Passive immunization
- Combined Immunization
- Antibiotic
- Symptomatic treatment:
(i) Endotracheal intubation and early tracheostomy
(ii) anti-spasmodic
(iii) Beta-blockers
5. Surgical debridement: Entry wound should be identified, cleaned and debrided of necrotic material, so as to remove the anaerobic foci of infection
6. Patient should be isolated in a separate room as any noxious stimulus (e.g. light) can aggravate the spasm
Passive Immunisation of tetanus
It is the treatment of choice for tetanus.
Two preparations are available:
1. HTIG (Human tetanus immunoglobulin), SII, Pune
2. ATS (Antitetanus serum, equine derived)
Dosage: 250 IU of HTIG or 1,500 IU of ATS single IM dose. Intrathecal route is more effective
Duration of protection:
HTIG 30 days
ATS 7–10 days
📝: HTIG is preferred over ATS as the latter is associated with side effects such as serum sickness and anaphylactoid reactions.
Combined Immunisation for tetanus
In nonvaccinated person, it is ideal to immunize with
- First dose of tetanus toxoid (TT) vaccine in one arm along with administration of
- ATS or HTIG in another arm, followed by
- Complete course of TT vaccine
When are antibiotics useful against tetanus
Which antibiotics are preferred
Antibiotics play only a minor role as they cannot neutralize the toxins which are already released.
However, they are useful:
1. In early infection, before expression of the toxin (<6 hours)
2. To prevent further release of toxin Metronidazole is the drug of choice; given for 7–10 days.
Penicillin or doxycycline can be given alternatively
