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Habitat of Corynebacterium diphtheriae
- Found in nasopharynx as well as in skin lesions, which actually represent a reservoir for the spread of diphtheria.
- Also found in mouth, throat, nose, skin and wound of infected person.
- Animals do not easily contract diphtheria.
- Patients carry toxigenic organism upto 3 months after infection.
Morphology of Corynebacterium diphtheriae
- They are gram +ve rod shaped bacteria.
- Club shaped
- Irregular swelling at one end or both end gives them the “Club Shaped” appearance.
- Thin and slender, long, curved
- Also known as Kleb’s-Loeffler Bacillus.
- 3 µm to 5 µm x 0.5 µm to 0.8 µm in diameter
- Chinese letter arrangement, V or L shaped
- Pleomorphic (Changes in shape and size of the bacteria)
- Seen in pairs or in small groups, appears in clusters
- Arranged in various angles to each other.
- Forms granules (metachromatic granules)
- Granules are the store house of energy
- Lipid rich cell wall contains mesodiaminopimelic acid, arabino-galactam polymers and short chain mycolic acid.
- Pili present
- Alberts’s stain and Ponder’s stain shows metachromatic granules formed in the polar regions
- Appears green in Alberts’s stain along with bluish black metachromatic granules at the poles.
Genome of Corynebacterium diphtheriae
- Contains 2389 Genes
- Protein encoding genes: 2272
- Have 69 Structural RNA gene
- Genome Length: 2,488,635 nucleotide
- 87% are coding
- G+C Content: 53%
- No plasmid
- Contains Pathogenicity Islands (PAI’s)