Clostridium Properties

  1. Clostridia are one of those bacilli which are gram positive.
  2. Obligate anaerobes,spore forming and highly pleomorphic.
  3. Shows stately motility and have peritrichate flagella.
  4. Cl. Welchi and Cl.tetani type VI do not have peritrichate flagella.
  5. Clostridia are normal residents of GIT and female genital tract.
  6. The only capsulated clostridia are Cl.Welchii and Cl.Butyricum.
  7. Cl. histolyticum is aerotolerant.
  8. Cl.Perfingens is most common Clostridium isolated from tissue infections

Cl.Perfingens/Cl.Welchii

  1. Capsulated and non motile.
  2. Stormy fermentation on litmus milk.
  3. Betahemolytic target hemolysis on blood agar.
  4. Virulence factor:Alpha toxin(Lecithinase C),destroys cell membranes.
  5. Naegler reaction:Alpha toxin in presence of in presence of Calcium and magnesium splits lecithin into phosphoryl choline and a  diglyceride.

Causes:

  1. Gasgangrene/Clostridial myonecrosis
  2. Gastroenteritis-Due to preformed heat labile enterotoxin, diarrhoea prominent but vomiting absent.
  3. Necrotising enteriti/Pigbel-Caused by beta toxin produced by type C strains.
  4. Emphysematous cholecystitis-MC in diabetics.

DOC:Penicillin,clindamycin,debridement.

To remember:Cl.perfingens most commonly isolated so it has alpha toxin and nonmotile because it causes gangrene.

Cl.Tetani

Drumstick appearance-due to terminal spores.

Toxins-Hemolysin/tetanolysin and neurotoxin/tetanospasmin.

Tetanospasmin is an exotoxin which acts presynaptically,it inhibits the release of inhinitory neurotransmitters and lead to unopposed stimulation of nerve.

Features:Lockjaw,risus sardonicus, death is usually due to respiratory failure.

Cl.Botulinum

  1. Subterminal spores
  2. Botulinum toxin is preformed heatlabile toxin,blocks release of acetylcholine.

Causes

  1. Classic botulism-Symptoms begin 1-36 hours after ingestion.Descending paralysis with significant bulbar effects.(Ocular paresis,diplopia,dysarthria,dysphagia,neuropathy),respiratory collapse.
  2. Wound botulism-spores in soil
  3. Infant botulism-bacterial spores in honey

Cl.Difficile

Virulence factors

  1. Toxin A is an enterotoxin binds to mucosal receptors , enter cell and cause fluid secretion and mucosal damage.
  2. Toxin B is a cytotoxin binds to Rho receptors on cell membrane and is 1000 times more potent.

Causes

  • Antibiotic associated colitis/pseudomembranous colitis-Clindamycin,penicillins,cephalosporins.
  • Diagnosed by identification of toxin in stool by tissue culture.
  • Epithelial ulceration with classic volcano exudates of fibrin and neutrophils.

DOC:Metronidazole(ist line),vancomycin.

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