CLOSTRIDIUMTETANI

Morphology The term “Clostridia” stands for spindle shape

Also known as Nicolaire's bacillus and belong to the phyllum firmicutes found in soil n GIT of animals

Size:4-8μm Shape:slender rods

Gram staining:predominantly gram positive bacilli maybe gram negative,exhibit pleomorphism(3%salt solution)

Posses peritrichous flagella and show motility except type IV

Spore forming bacteria,appear as“tennisracket”/”drumstick shaped” due to presence of terminal spores in mature bacteria

CULTURE CHARACHTERISTCIS• Obligate anaerobes

• Blood agar: Initially alpha haemolytic then later changes to beta haemolysis due to production of toxin tetanolysin(haemolysin)

• Surface colonies tend to swarm produce an extremely fine translucent film of growth

• Fildes technique:bacteria innoculated at the bottom of nutrient agar slope kept in anaerobic incubation for 24hrs- pure colony at the top of the slope

• Robertson cooked meat medium:bacteria grow well,meat is not digested but bacteria show turbidity and gas production.

• Bacteria liquifies gelatin fir tree type of growth is seen

BIOCHEMICAL REACTIONS• Lacks saccharolytic activity hence does not ferment

any sugars

• Does not reduce nitrates,does not produce H2S

• Catalase +ve

• Indole +ve

• Citrate -ve

• Methyl red -ve

• Vogues proskauer -ve

• Mannitol not fermented shows motility

Pathogenesis• It is a non invasive organism localized in the area of

devitalisation(wound,incision,burn)

• The disease is caused due to the production of toxins (toxemia)

• Spores germinate into to vegetative bacilli in the presence of necrotic tissue,calcium salts and asso pyogenic infections which offers Low redox potential and favours growth

• The toxins then travel to the CNS and get attatched to the receptors in spinal cord and brain stem.

The toxins produced are

Tetanospasmin-heat labile protein of MW150000

Tetanolysin-Oxygen and heat labile haemolysin

Neurotoxin

• Tetanospasmin is the main toxin responsible for the clinical manifestation of tetanus

• It is cleaved by an endogenous protease in the bacteria to two peptides linked by a di sulphide bond which now attaches itself to the receptors of the spinal cord and brain stem.

CLINICAL MANIFESTATIONS • Incubation period varies from 4-5 days to weeks

• Painful tonic contractions

• Generalised muscle rigidity with with reflex spams to touch or stimuli

Trismus or lockjaw

Opisthotonus-Arched back with adducted arms,closed fist,extension of lower extremities

• Risus sardonicus- a characteristic sardonic smile

• It is a highly fatal disease and death isprimarily due to respiratory muscle paralysis

• Localised tetanus,Cephalic tetanus,Neonatal tetanus

Lab diagnosis• Excised bits of necrotic tissue is anaerobically

cultured to show presence of bacteria

• Gram staining,culture and bio chemical test properties are confirmed

• Toxigenicity test: In vivo neutralisation on blood agar(4%agar) innoculated with tetanus antitoxin on one half.There is haemolysis in the area not coated with antitoxin& absence of haemolysis/growth around the area of antitoxin

• In mice 0.2 ml of culture is inoculated in the the root of the tail of two mice one immunized with 1000 units of antitoxin before the test.The other mice develops tetanus in 12-24 hours and the animal dies in 48 hrs

• There is no antibody to the tetanus toxin produced in the body or methods to detect toxin in serum hence serological tests are not used

• Clinical test -Spatula test in which the oropharynx is touched using a spatula to initiate the gag reflex.the patient tried to expel the spatula but instead develops a reflx spasm of the masseter and bites the spatula

• Differential diagnosis: Strychnine poisoning

PROPHYLAXIS AND TREATMENT• Equine tetanus antitoxin (ATS)-hypersensitivity

• Active immunization with Tetanus toxoid- prepared by detoxifying it with formalin and then concentrating it.It may be given as plain toxoid or adsorbed with aluminium salt.

• DPT(Diptheria pertussis tetanus vaccine)where pertussis acts as an adjuvant.3 doses i.m interval of 4-6weeks between first two injections and 3rd dose is given 6months later.The person is rendered immune for a period of 10yrs.

Toxoid preparations should not be given to an already immunized individual however booster doses may be given.Frequent administration is avoided-hypersensitivity

• Antitoxin prophylaxis- Administration of 250-500 units of human antitetanus immunoglobulin (TIG) tetanus antitoxin renders the patient systemic protection for 2-4 weeks by neutralizing the toxin that is not bound to nervous tissue.3000-6000 units i.m in children n adults on diagnosis ,500IU for infants

• “Recall” injection of toxoid along with the antitoxin is given in case of a potentially dangerous wound

• Surgical debridement of infected area may be done

• Penicillin,Metronidazole,Tetracyclin,clindamycin, vancomycin, erythromycin are used.

• Muscle relaxants,sedation and assisted ventilation is given

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