Corynebacterium diphtheriae.

(genus C. diphtheriae)

Morphology
-Gram positive, non acid fast, non sporing, non motile bacilli.
-Thin, slender, pleomorphic, non capsulated
-Show club shaped swelling (coryne) due to metachromatic granules at both ends.
-with Albert’s stain – green rod shaped resembling ‘L’ @ ‘V’ @ Chinese letter pattern @ cuneiform (due to incomplete separation of daughter cells after binary fusion) with bluish black metachromatic granules at the poles.

metachromatic granules
-also called babe Ernst granules @ volutin
-take up bluish purple colour of loeffler’s methylene blue
-composed of polymetaphosphates
-f(x)- energy storage

Cultural characteristics.
- Grow best in enriched media.
- Scanty in ordinary media.
- Aerobic (facultatively anaerobic)
- Temp=15-40c
- pH7.2
- eg; loeffler’s serum slope, tellurite blood agar.

Biochemical reactions.
- Ferment glucose n maltose
- Reduces nitrates to nitrites
- Not hydrolyse urea.

Toxin.
- Pathogenicity due to production of powerful exotoxin by its virulent strains.
- Action- inhibiting protein synthesis.
- Dies at 58c for 10mins @ 100c for 1min.
- Resistant to drying
- Susceptible to panicilin.
- Seen in children (2 – 10yrs)
- Incubation period =3 – 4 days
- Spreading= droplet
- Site= nasal, laryngeal, conjunctival , vulvovaginal.
- Local effect= toxin causes local necrotic changes and inflammatory reaction --> pseudomembrane
- Systemic effect= toxin diffuse into blood stream, have affinity towards cardiac muscle, adrenals, nerve ending.

Laboratory diagnosis
- Isolation organism;
o Collection of specimen
o Direct microscopy- gram stain n Albert’s stain
o Culture
§ loeffler’s serum slope= colonies are small, circular white @creamy
§ Potassium tellurite agar= black @ grey colonies
- Virulence test.

Diphtheroids
- Commensals corynebacteria
- Present in throat, skin.
- Few or no metachromatic granules
- Arranged parallel.

p/s; semoga sedikit sebanyak dapat membantu..insyaAllah