Diphtheria

Diphtheria
1. is an upper respiratory tract illness
2. Characterized by sore throat, low fever, and an adherent membrane (a pseudomembrane) on the tonsils, pharynx, and nasal cavity.
3. Caused by Corynebacterium diphtheriae, an aerobic Gram-positive bacterium, 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") and sometimes which have clubbed ends . The bacterium may contain polymetaphosphate aggregates called Volutin granules. It is pathogenic only in humans. C. diphtheriae produce diphtheria toxin,
Classification:
1. C. diphtheriae mitischodis,
2. C. diphtheriae intermedius,
3. C. diphtheriae gravis,
4. C. diphtheriae belfanti.
The four subspecies differ slightly in their colonial morphology and biochemical properties such as the ability to metabolize certain nutrients, but all may be toxigenic (and therefore cause diphtheria) or non-toxigenic.
Diagnosis:
Gram stain:
Gram-positive, highly pleomorphic organisms with no particular arrangement (classically resembling Chinese characters). Then, culture the organism on an enrichment medium, namely Löffler's serum, to allow it to overgrow any other organisms present in the specimen. After that, use a selective plate known as tellurite agar which allows all Corynebacteria (including C. diphtheriae) to reduce tellurite to metallic tellurium producing brown colonies and, only in the case of C. diphtheriae, a black halo around the colonies allowing for easy differentation of the organism.
Sensitivity:
The bacterium is sensitive to the majority of antibiotics, such as the penicillins, ampicillin, cephalosporins, quinolones, chloramphenicol, tetracyclines, cefuroxime and trimethoprim