Most common stain used for staining of metachromatic granules :
Ans: a (Alberts stain) Ref: Ananthanarayan,7th ed, p. 231Most common stain used for staining of metachromatic granule is Albert stain.Metachromatic granules of diphtheria are also known as Babes Ernst or volutin granules which are composed of polymetaphosphate and are more strongly gram positive.Special stains to see metachromatic granules areAlbert stainNeisser stainPonder stainCorynebacterium diphtheria: (Klebs Loefflers bacillus)- Characteristically club shaped, pleomorphic, non capsulated non sporing bacilli- Arranged in pairs palisades, cluster and is known by the name "Chinese letter or cuneiform arrangement.Selective medium- Tellurite blood agar (2 days) or tinsdale mediumBut for rapid growth, Loeffler serum slope is used (6-8 hours)Diphtheria toxin:Theorthopaedic disease in which histology revealsChinese letter pattern is fibrous dysplasia.Polypeptide exotoxin, production depends on iron concentration.It is composed of two fragments- fragment B for bindingFragment A (enzymatic activity) for inactivating EF-2 in presence of NAD.Hence it inhibits protein synthesis. Toxin acts both locally and systemically while bacilli remain localized.Hence diphtheria is toxaemia not bacteraemia.Corynophage controls production of toxin, hence it shows lysogenic or phage conversion.The strain almost universally used for toxin production is the "Park William 8 strain."DiagnosisIsolation on tellurite medium. Eleks gel precipitation is in vino test which indicates toxigenicity.Treatment:Antitoxin most important element in respiratory diphtheriaAntitoxin does not prevent colonization nor eradicates carrier stateDOC -Erythromycin or procaine penicillin GGlucocorticoids do not reduce the risk of myocarditis or polyneuropathAlso:Shick test: susceptibility test for diphtheriaDick test: susceptibility test for scarlet fever.
Albert's
Geimsa
AFB
Wayson
Corynebacterium