Tetanus (Medical Microbiology)

TetanusTetanusisanacute,oftenfatal,diseasecausedbyanexotoxinproducedbyClostridiumtetani.Itischaracterizedbygeneralizedrigidityandconvulsivespasmsofskeletalmuscles.Themusclestiffnessusuallyinvolvesthejaw(lockjaw)andneckandthenbecomesgeneralized.Minimalinflammationandevenunnoticedwoundinmostofthecases.C. tetani is a slender, gram-positive, anaerobic rod that may develop a terminal spore, givingit a drumstickappearance.The vegetative organism is sensitive to heat and cannot survive in the presence ofoxygen.ClostridiumtetaniThe spores, in contrast, are very resistant to heat and the usual antiseptics surviving autoclaving at 121C for 10-15minutes.The spores are also relatively resistant to phenol and other chemicalagents.Thesporesarewidelydistributedinsoilandintheintestinesandfecesofhorses,sheep,cattle,dogs,cats,rats,guineapigs,andchickens.Spores also present in human skin.Cellular MorphologyRod shaped, pleomorphic2-5 x 0.5-1 umMotile with peritrichous flagellaTerminally located spores with greater diameterCultural CharacteristicsTemperature range rom 20-45 C (optimum temp: 37 C)Alkaline pH10% CO2Require amino acids, vitamins, purines and oleic acidBlood agar, chopped meat glucose medium, egg yolk agar2-5 nm flat, irregular, rhizoid, glistening, translucent colonies with irregular granular surfaceGrowth may be swarming with an offensive odor of manure.Organisms are not biochemically activeDo not ferment carbohydratesExhibit; Gelatin liquificationMeat digestion in brothIndole productionLecithinaseand lipase activityhemolysisCl. TetaniToxins(Pathogenesis)TWO important exotoxins (tetanolysin andtetanospasmin)are produced by vegetativeorganisms:-The genes that produce toxin are encoded on a plasmid which is present in all toxigenic strains, and all strains that are capable of producing toxin produce identical toxinThefunctionoftetanolysinisnotknownwithcertainty.Tetanospasminisaneurotoxinandcausestheclinicalmanifestationsoftetanus.Onthebasisofweight,tetanospasminisoneofthemostpotenttoxinsknown.Thehumanlethaldoseis2.5nanogramsperkilogramofbody(2.5ng/Kg).Tetanospasminis distributed in the blood and lymphatic system of the host. The toxin acts at several sites within the central nervous system, including peripheral nerve terminals, the