Elek's gel precipitation test is used to detect toxicity of?
Ans. d (C.diphtheriae) (Ref. Ananthanarayan, Microbiology, 8th/ p. 236)Toxin production can be detected by precipitation with ab in an Elek's plate = a basis for Elek's gel precipitation test.The presence of arrow head lines of precipitates indicates that the strain of Corynebacterium diphtheriae is toxigenic.Virulence tests for Corynebacterium diphtheriaeIn vivoIn vitro1. Subcutaneous test1. Eleck's gel precipitation test (very convenient & economical)2. Intracutaneous test2. Tissue culture testCorynebacterium diphtheriae# Nonmotile, Aerobic, Nonsporing, Catalase + Gram-positive club-shaped rods/bacilli.# Grows slowly on selective media containing tellurite.0# Colonies appear black because bacterium breaks down tellurite to metallic tellurium which is accumulated.# Grows rapidly on enriched media like Loffler's serum slope.Q# Commensals in human body (commonly on skin)# Humans are the only natural hosts# Rarely causes diseases, mainly seen in areas of poor hygiene and no immunization.# Causes lesions (diphtheria) in Upper Respiratory Tract.# Skin lesions may occur due to toxigenic and nontoxigenic strains.# Along with Coagulase-Negative Staph, it is frequent cause of subacute endophthalmitis following cataract surgery.# Mode of entry is by inhalation.# Attaches to the back of throat of children, followed by secretion of diphtheria toxin which kills cells and causes inflammation and fibrin accumulation, leading to formation of characteristic pseudomembrane.# If toxin enters the bloood stream, it can also affect heart and CNS.# No innate immunity to the toxin, but adults are generally more resistant to throat infection.
E. coli
H. influenzae
N. gonorrhoea
C.diphtheriae
Bacteria