Corynebacterium diphtheriae
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 Gram stained Corynebacterium diphtheriae culture
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| Corynebacterium diphtheriae Kruse, 1886 |
Corynebacterium diphtheriae is a pathogenic bacterium that causes diphtheria. It is also known as the Klebs-Löffler bacillus, because it was discovered in 1884 by German bacteriologists Edwin Klebs (1834 – 1912) and Friedrich Löffler (1852 – 1915).
C. diphtheriae is a facultatively anaerobic [1] Gram positive organism, characterized by non-encapsulated, non-sporulated, immobile, straight or curved rods with a length of 1 to 8 µm and width of 0.3 to 0.8 µm, which form ramified aggregations in culture (looking like "Chinese characters"). It is not pathogenic only in humans.
Many strains of C. diphtheriae produce diphtheria toxin, a proteic exotoxin, with a molecular weight of 62 kilodaltons which ADP-ribosylates host EF-2, which is responsible for the signs of diphtheria. The inactivation of this toxin with an antitoxic serum (antitoxin) is the basis of the antidiphtheric vaccination. However, not all strains are toxigenic; toxin production is associated with infection of the bacterium by a bacteriophage.
Three subspecies are recognized: C. diphtheriae mitis, C. diphtheriae intermedius, and C. diphtheriae gravis. The three subspecies differ slightly in their ability to metabolize certain nutrients, but all may be toxigenic (and therefore cause diphtheria) or non-toxigenic.
The bacterium is sensitive to the majority of antibiotics, such as the penicillins, ampicillin, cephalosporins, quinolones, chloramphenicol, tetracyclines, cefuroxime and trimethoprim.
[edit] External links
- CoryneRegNet - Database of Corynebacterial Transcription Factors and Regulatory Networks
