TETANUS

TETANUS• Tetanus is a

medical condition characterised by prolonged contraction of skeletal muscle fibres.

Introduction• Primary symptoms by-tetanospasmin, a

neurotoxin produced by the Gram-positive, obligate anaerobic bacterium Clostridium tetani.

• Infection generally occurs through wound contamination, & often involves a cut or deep puncture wound.

Introduction• As the infection progresses, muscle

spasms in the jaw develops, hence the common name, lockjaw.

• This is followed by difficulty swallowing & general muscle stiffness & spasms in other parts of the body.

• Infection can be prevented by proper immunisation & by post-exposure prophylaxis.

Clostridium tetani• Cl.tetani is widely

distributed in soil & in intestine of human beings & animals.

• They cause tetanus in both man & animal.

Morphology• Gram-positive, 4-

8µm×0.5µm bacillus.

• Has straight axis, parallel sides & rounded ends.

• Occurs singly & occasionally in chains.

• It is capsulated & motile with peritrichate flagella (except typeVI Cl. tetani-nonflagellar strain).

• Young cultures are strongly Gram positive but older cells show variable staining & may be even Gram negative.

Morphology

Cultural characteristics• It is an obligatory anaerobe (grows only in

absence of oxygen).• Optimum temparature-37°C & pH-7.4.• It grows on ordinary media.

Cultural characteristics• 1.Robertson’s cooked meat medium:

turbidity & some gas formation. The meat is not digested but turns black on prolonged incubation.

• 2.Blood agar: fine translucent film of growth.α hemolysis is produced, which later develops into β hemolysis, due to the production of hemolysin (tetanolysin)

Cultural characteristics• 3.Deep agar shake cultures: spherical

fluffy balls, 1-3mm in diameter, made of filaments with radial arrangement.

• 4.Gelatin stab culture: fir tree appearance with slow liquefaction.

Spore• The spores are

spherical, terminal & bulging, giving the bacillus the characteristic ‘drumstick’ appearance.

• Morphology depends on stage of development.

• Young spore may be oval rather than spherical.

Biochemical reactions• Feeble proteolytic but no saccharolytic property.• Forms indole.• MR & VP negative.• H2S is not formed.• Nitrates are not reduced.• Gelatin liquefaction-slow.• Greenish fluorescence produced on media

containing neutral red.

Resistance• Spore resistance to heat show strain

variation.• Majority are killed by boiling for 15min.• Some withstand boiling for 3hr & dry heat

at 160°C for 1hr.• Spores can survive in soil for years & are

resistant to most antiseptics.• Not destroyed by 5% phenol or 0.1% HgCl2

solution in 2 weeks or more.

Susceptibility• Autoclaving at 121°C for 15min kills the

spores readily.• Iodine(1% aqueous soon) and H2O2 (10

volume) kills spores within few hours.

Toxins• All types produce same toxins which

are pharmacologically & antigenically identical.

• Plasmid mediated.• 1.Tetanolysin• 2.Tetanospasmin

Tetanolysin

• Heat & O2 labile hemolysin.• Cause red cell lysis.• Pathogenic role not clear.• May act as leucocidin.

Tetanospasmin

• O2 stable & heat labile neurotoxin.• Good antigen & specifically

neutralised by antitoxin.• Similar to botulinum toxin in str.• Gets toxoided spontaneously or in

presence of formaldehyde.

Pathogenesis• Usual mode of infection-Penetrating

injury.• Germination & toxin production

occurs only in favorable condition-↓OR potential, devitalised tissues, foreign bodies, concurrent infection.

• Resembles strychnine poisoning

Antigens• All strains share common somatic (O)

antigen.• On basis of flagellar (H) antigen 10 types(Ι

to X) are recognised by agglutination tests.

• Type VI is non-flagellated strain.

1.Local tetanus Persistent spasm of

musculature at site of primary infection (injury site).

Contractions persist for weeks before subsiding.

Its generally milder, 1% cases are fatal but may precede the generalised tetanus.

2.Cephalic tetanus• Primary site of infection is head injury or

otitis media.• Associated with disfunction of 1 or more

cranial nerves, most commonly facial nerve.

• Poor prognosis.

3.Generalised tetanus• Most common form(80%

of cases).• Presents with a

descending pattern.• 1st sign is trismus(lockjaw)

-due to spasm of masseter muscles.

• Followed by stiffness of the neck, difficulty in swallowing, rigidity of abdominal muscles.

Risus sardoricus• Characteristic

sardonic smile in tetanus

• Results from sustained contraction of facial muscles.

Opthisthotonus• Back spasm seen in

tetanus

4.Tetanus neonatorum• It is the

generalised tetanus that occurs in newborn infants.

• Occurs in infants of non-immunised mothers.

Tetanus neonatorum• Occurs from infection

of un-healed umbilical stump particularly when stump is cut with non-sterile instrument.

• Very poor prognosis

Laboratory diagnosis• Diagnosis made based on

clinical presentation.• Specimen: Wound swab,

exudate or tissue from the wound.

• 1.Direct smear & gram staining

• 2.Culture• 3.Animal inoculation

Direct smear• Show Gram-positive

bacilli with drum-stick appearance.

• Morphologically indistinguishable from similar nonpathogenic bacilli.

Culture• Done in blood agar & aminoglycoside

blood agar under anaerobic condition or in Robertson’s cooked meat medium.

• Produces swarming growth after 1-2 days of incubation.

• In contaminated specimen heat at 80°C for 10mins before culture to destroy non-sporing organisms.

Animal inoculation• To demonstrate

toxigenicity.• Positive case : test

animal develops stiffness & spasm of tail & inoculated hind limb within 12-24hrs which spreads to rest of the body. Death occurs in 1-2 days.

Prophylaxis• 1.Surgical attention• 2.Antibiotics• 3.Immunisation-passive,active or

combined.

Surgical Prophylaxis Aims at removal of foreign bodies,

necrotic tissue & blood clots,

To prevent an anaerobic envt favourable for the Clostridium tetanae

Antibiotic prophylaxis• Aims at destroying or inhibiting tetanus

bacilli & pyogenic bacteria in wounds so that toxin production is prevented.

• Long-acting Penicillin is the drug if choice. Erythromycin is an alternative.

• Bacitracin or neomycin can be applied locally.

• Has no action on toxin.

Immunisation• Combined immunisation:

Tetanus immunoglobulin(TIG) & tetanus toxoid are given on different arms.

• Provides both passive & long-lasting immunity.

Treatment• Isolate pt. from noise &

light which may provoke convulsions.

• Followed by supportive care.

• TIG is infused.• Antibacterial therapy

started.

Epidemiology• World wide

distribution- higher in developing countries due to warm climate, unhygienic practices & poor medical services.

Prevention & control• By active immunisation

with tetanus toxoid.1.TT-2 doses for pregnant

women,2.DPT at 6, 10, 14 weeks

after birth,3.DPT booster at 18 months4.DT at 5yrs.5.TT boosters at 10 & 16 yrs.