Elek's test

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Elek's test, also known as the immuno diffusion technique, is an in vitro virulence test performed upon Corynebacterium diphtheriae.[1] It is used to test for toxigenicity of C. diphtheriae.

It was characterized in 1949 by the American Microbiologist, Stephen Dyonis Elek (1914–1992).[2] A filter paper strip impregnated with diphtheria antitoxin is buried just beneath the surface of a special agar plate before the agar hardens. Strains to be tested, known positive and negative toxigenic strains are streaked on the agar's surface in a line across the plate, and at a right angle to the antitoxin paper strip. After 24 hours of incubation at 37 degrees Celsius, plates are examined with transmitted light for the presence of fine precipitin lines at a 45-degree angle to the streaks. The presence of precipitin lines indicates that the strain produced toxin that reacted with the antitoxin.


  1. ^ Schubert JH, Bickham ST, Wiggins GL (November 1968). "Tissue culture method for toxigenicity testing of Corynebacterium diphtheriae". Appl Microbiol. 16 (11): 1748–52. PMC 547753Freely accessible. PMID 4973065. 
  2. ^ ELEK SD (November 1949). "The plate virulence test for diphtheria". J. Clin. Pathol. 2 (4): 250–8. doi:10.1136/jcp.2.4.250. PMC 1023322Freely accessible. PMID 15396422. 

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