*CLOSTRIDIUM TETANI SARANYA B GOMATHY 2ND M.B.BS TRAVANCORE MEDICAL COLLEGE, KOLLAM KERALAMORPHOLOGYRelatively large, Gram-positive, slender bacillus with straight axis, parallel sides & rounded ends.Occurs singly, occasionally in chainsSpores are spherical, terminal & bulging—drumstick- appearanceNon-capsulated and motile by peritrichate flagellaFound in soil, especially heavily-manured soils, and in the intestinal tracts and feces of various animalsStrictly fermentative mode of metabolism.CULTURAL CHARACTERISTICSObligate anaerobe; 37 degrees C and pH 7.4Grows on ordinary mediaSurface colonies swarming over surface of agar.If water of condensation at the bottom of a slope of nutrient agar is inoculated with mixed cell culture,after incubation for 24h, subcultures from the top of tube will yield a pure growth of the bacillus. (Fildes’technique)Deep agar shake cultures—spherical fluffy ball coloniesGelatin stab cultures—fir tree type of growthGrows well in RCMBlood agar-alpha followed by beta hemolysis (tetanolysin)VIRULENCE AND PATHOGENICITY Not pathogenic to humans and animals by invasive infection but by the production of a potent protein toxin
tetanus toxin or tetanospasmin The second exotoxin produced is tetanolysin—function not known.Produced when spores germinate and vegetative cells grow after gaining access to wounds. The organismmultiplies locally and symptoms appear remote from the infection site.Estimated lethal human dose ofTetanospamin = 2.5 Nano grams/kg bodyThe toxin has a specific affinity for nervous tissue, it is referred to as a neurotoxinInitially binds to peripheral nerve terminalsTransported within the axon and across synaptic junctions until it reaches the central nervous system.Becomes rapidly fixed to gangliosides at the presynaptic inhibitory motor nerve endings, then taken upinto the axon by endocytosis.Blocksthe release of inhibitory neurotransmitters (glycine and gamma-amino butyric acid) across thesynaptic cleft, which is required to check the nervous impulse.If nervous impulses cannot be checked by normal inhibitory mechanisms, it leads to unopposed muscularcontraction and spasms that are characteristic of tetanus.METHODS OF TRANSMISSIONC. tetani can live for years as spores in animal feces and soil. As soon as it enters the human body througha major or minor wound and the conditions are anaerobic, the spores germinate and release the toxins.Tetanus may follow burns, deep puncture wounds, ear or dental infections, animal bites, abortion.Only the growing bacteria can produce the toxin.It is the only vaccine-preventable disease that is infectious but not contagious from person to person.SYMPTOMS Tetanic seizures (painful, powerful bursts of muscle contraction) if the muscle spasms affect the larynx or chest wall, they may cause asphyxiation stiffness of jaw (also called lockjaw) stiffness of abdominal and back muscles contraction of facial muscles, fast pulse, fever, sweatingTYPES OF TETANUS Incubation period: 3-21 days, average 8 days.
UNCOMMON TYPES:Local tetanus: persistent muscle contractions in the same anatomic area as the injury, which willhowever subside after many weeks; very rarely fatal; milder than generalized tetanus, although it couldprecede it.Cephalic tetanus: occurs with ear infections or following injuries of the head; facial muscles contractionsMost common types:Generalized tetanus - Descending pattern: lockjaw (trismus) stiffness of neck difficulty swallowing rigidity of abdominal and back muscles. (Opisthotonus) - Spasms continue for 3-4 weeks, and recovery can last for months - Death occurs when spasms interfere with respiration.Neonatal tetanus: - Form of generalized tetanus that occurs in newborn infants born without protective passive immunity because the mother is not immune. - Usually occurs through infection of the unhealed umbilical stump, particularly when the stump is cut with an unsterile instrument.LAB DIAGNOSISBased on the patient’s account and physical findings that are characteristic of the disease.Diagnostic studies generally are of little value, as cultures of the wound site are negative for C. tetanitwo-thirds of the time. When the culture is positive, it confirms the diagnosis of tetanusTests that may be performed include the following: Culture of the wound site (may be negative even if tetanus is present) Tetanus antibody test Other tests may be used to rule out meningitis, rabies, strychnine poisoning, or other diseases with similar symptoms.PROPHYLAXIS 1. Surgical attention 2. Antibiotics
3. Immunization-Active, Passive, CombinedSurgical- removal of foreign bodies, necrotic tissue & blood clotsAntibiotics-destroy or inhibit the bacilli in wounds so that toxin production is prevented. Long actingpenicillin inj or erythromycin (500mg b.d for 5 days). To be started before wound toilet. Neomycin orbacitracin may also be applied locallyPassive immunization-ATS from hyper immune horses-1500U s/c or i/m in nonimmune personssoon after receiving any tetanus prone injury. (Risk of hypersensitivity)TIG-250U, has a longer half-lifeActive immunization-most effectiveAchieved by spaced inj of formal toxoid (plain/adsorbed). The tetanus toxoid is given either alone oralong with diphtheria toxoid and pertussis vaccine (DPT/ triple vaccine)3 doses of TT i/m, with an interval of 4-6 wks between the first two inj and the 3rd dose 6 months later. Afull course of immunization confers immunity for a period of at least 10 yrsCombined immunizationTIG inj at one site, along with 1st dose of TT at the contralateral site, followed by 2nd& 3rd doses of toxoid(adsorbed) at monthly intervalsTREATMENTIsolate pt from noise and light (may provoke convulsions)Control spasms using muscle relaxantsMaintain airway by tracheostomy with intermittent positive pressure respiration & attention to feedingHuman TIG 10,000U suitably diluted—given IVAntibacterial therapy-penicillin or metronidazolePatients recovering from tetanus should receive a full course of active immunizationAnswering a question is an art, which has to be perfected. Our student in Microbiologywrites the article on Clostridium tetani as part of problem solving question in AppliedMicrobiology. The answer is well-scripted and expressing solutions with a scientific spirit.If this methodology is followed every one can score the best.The article is published as part empowering the Students