Corynebacterium

Corynebacterium

Gram positive rods:

Organism belonging to the genus :  Corynebacterium ( koryne’Greek=Club) are gram positive rods’ arranged in pairs and in palisades. They have metchromiatic granules, are often club shaped and frequently show involution forms. They are non-molite, non-sporing,non –capsulated and non- acid –fast, C. diphtheria is the causative organism for diphtheria in human beings. It is generally termed as KLB (Klebs-Loeffler Bacillus).

Classification of Corynebacterium:

Corynebacterium two types:A. Pathogenic species                          B. Non –pathogenic species.

1. C. diphtheria                                    a. C. hofmanie
2. C. ulcerans                                       b. C.xerosis
3. C.haemolyticum                               c. C.acnes
4. C. pseudotuberculosis.                     d. C. pseudogenitalium
5. C. reanle                                           e. C. pseudodiphtheriticum.

Corynebacterium diphtheria:

Habitat: Nose, nasopharynx ,throat.

Morphology of Corynebacterium diphtheria:

Shape       : Club shaped

Size          : 3-5  µm in length.

Arrange   : In pair (like V &L)

Spore       : Absent

Capsule   : Absent

Motility   : Non –molile.

Staining   : They are gram positive and non-acid –fast.

Cultural character:

1.  Aerobic and facultative anaerobes.
2. Optimum Ph : 7.2
3. Optimum temperature : 37°C.
4. Growth:

1. On telluride agar media : colonies are black ,small ,smooth circular and opaque.
2. On Loeffer’s serum slope: colonies are small, 1 mm in diameter , smooth circular & opaque,
3. On blood agar media: colonies are haemolytic.

Biochemical character:

- They ferment various sugars.

- They produce acid but no gas.

Pathogenic effects of Corynebacterium diphtheria:

1. Effects of bacilli themselves:

- Formation of a pseudo –membrane (thick, gray, adherent),

2. Effects of exotoxin:

• Pyrogenic effect: fever.
• Tissue poisoning effects on:

Heart : toxic myocarditis , fatty degeneration and acute circulatory failure .

Blood vessels: peripheral circulatory failure.

Kidneys : Nephritis and interstitial nephritis.

Adrenal gland: Hemorrhage.

Nerves: toxic neuritis.

3. Effects of secondary ihvaders:

• High fever
• Bronchopneumonia.
• Cervical lymphadenitis.
• Streptococcal septicemia.