TETANUS By Chandana Krishna 4 th term B.M.C

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. H 2 S 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% HgCl 2 solution in 2 weeks or more.

Susceptibility Autoclaving at 121°C for 15min kills the spores readily. Iodine(1% aqueous soon) and H 2 O 2 (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 & O 2 labile hemolysin. Cause red cell lysis. Pathogenic role not clear. May act as leucocidin.

Tetanospasmin O 2 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. 1 st 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 months 4.DT at 5yrs. 5.TT boosters at 10 & 16 yrs.

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