Clostridium

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Clostridium

  • large Gram +ve rods
  • anaerobic
  • spore forming 
  • pathogenic species usually produce toxins 
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Neurotoxic and histotoxic Clostridia

  • neurotoxic clostridia
    • C. tetani (tetanus) - horses, ruminants, birds, humans etc
    • C. botulinum (botulism) - many animal species and humans 
  • histotoxic clostridia 
    • C. chauvoei (blackleg) - cattle, sheep and occasionally pigs
    • C. septicum (malignant oedema) - cattle, sheep and pigs 
    • C. novyi  Type A - (bighead in rams, gas gangrene) - rams cattle sheep. Type B (black disease, acute toxaemia and necrotic hepatitis) - mainly sheep also cattle 
    • C. sordellii (gas gangrene) - cattle, sheep, horses 
    • C. perfringens Type A (gas gangrene) - humans, dogs
    • C. haemolyticum (bacillary haemoglobinuria) - cattle and sheep 
    • C. colinum (ulcerative enteritis) - chickens, turkeys, and game birds 
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C. tetani

  • gram +ve anaerobes 
  • terminal spores
  • found in soil and intestine 
  • 10 serological types
  • 1 toxin type 
  • infects through wounds
  • spores germinate in tissues resulting in toxin production
  • toxin transported along axon to reach CNS where it blocks release of GABA or glycine from inhibitory interneurons 
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Tetanus - diagnosis, treatment and prevention

  • clinical signs 
    • rigidity of muscles, spasms, opisthotonos, raised tail, difficult respiration
  • toxin identification 
    • laboratory animals with and without serum 
  • treatment 
    • surgical debridement of wound
    • sedation and tranquilisers 
    • anti-microbials and antitoxin are of limited value once symptoms appear 
  • prevention 
    • toxoid administration (vaccine), immuno-therapy and antibiotics for immediate prophylaxis
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C. botulinum

  • oval sub-terminal spores 
  • eight different neurotoxins 
  • C2 and C3 toxins - ADP ribosylating toxins 
  • found in soil
  • disease usually due to ingestion of pre-formed toxin 
  • wound botulism and infant intestinal toxico-infection are more rare 
  • spores germinate in anaerobic environments 
    • cans of meat fish veg
    • carcasses of animals 
    • rotting plants
    • baled silage
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Botulinum pathogenesis

  • spores in environment
  • contamination of food, veg, animal carcasses
  • germination of endospores and toxin production
  • ingestion of toxin
  • transport via blood stream to peripheral nerve ends 
  • inhibition of acetylcoline release
  • flaccid paralysis 
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Botulism - diagnosis, treatment and prevention

  • clinical signs
    • flaccid paralysis, circulatory failure, respiratory paralysis 
  • toxin identification in serum or in foodstuff 
    • inoculation iv or ip into mice with/without antiserum, food is macerated overnight in saline and centrifuged, supernatant is filtered and 9 parts of filtrate are treated with 1 part 1% trypsin 
  • treatment 
    • intravenous antitoxin 
    • trachotomy and assisted ventilation 
  • immunisation 
    • toxoid based vaccines are available 
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Clostridium chauvoei

  • found in intestine and normal tissues - not common in soil 
  • toxins
    • alpha - haemolysin, necrotising
    • beta - deoxyribonuclease
    • gamma - hyaluronidase 
    • delta - haemolysing 
  • spores enter by ingestion - carried to muscle via lymph or blood - trauma in muscles creates anaerobic conditions where spores germinate, bacteria replicate and toxins are released - localised damage is followed by terminal toxaemia and bacteriaemia 
  • wound infection is possible 
  • black leg - necrosis of the muscle, gas bubbles, rancid odor
  • vaccine preparations are based on formalinised cultures possibly with adjuvants
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Clostridium septicum

  • malignant oedema 
  • found in intestine and soil 
  • pathogenesis associated with exogenous infection through wounds or endogenous infection followed by tissue destruction due to toxins that damage tissue components
    • alpha - lethal necrotising (lecithinase)
    • beta - deoxyribonuclease 
    • gamma - hyaluronidase 
  • C. septicum causes malignant oedema and gas gangrene and affects mainly horses, cattle, sheep, and pigs 
  • endogenous infection of sheep is associated with necrotic lesions and haemorrhagic oedema of the abomasal and duodenal wall 
  • vaccine preparations - formalin killed cultures, possibly with adjuvants 
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