Corynebacterium diphtheriae

  1. Gram Stain appearance?
    Small GPB, often presenting as cocco-bacillary, pleomorphic, pallisades or chinese letter like appearance.
  2. Media
    • SBA:
    • Small, grayish white may or may not be hemolytic

    • Tellurite Cysteine Agar CTBA:
    • Small Black colonies

    • Tinsdale:
    • Grayish black colonies with a brown halo
  3. Biochemical tests
    • Negative:
    • Urease
    • Positive:
    • Nitrate & Catalase
    • Variable:
    • Esculin & Motilitiy

    • Toxin testing: (tests for toxin phage
    •    in vitro: culture and antitoxin in rabbit
    •    in vitro: immunodiffusion
  4. Epidemiology
    • Usually presents as a repiratory disease or occasionally cutaneous inf.
    • Spread person to person

    Rare due to vaccinations.
  5. Pathogenesis & virulence factors
    • Invasion: bacterai colonize and proliferate in local tissues of the throat creating pseudomembrane.
    • Toxigenesis: Bacteria produce an exotoxin which causes the death eukaryotic cells and tissues by inhibition of cell protein systhesis.
  6. Susceptibility treatment
    Penicillin or erythromycin
  7. C. jeikeium
    • Normal on skin
    • disease causing in some immunocompromised or noscomial 
    • Antimicrobial resistance.
    • Line related infections
Card Set
Corynebacterium diphtheriae