Elek's test or the Elek plate test is an '' in vitro'' test of virulence performed on specimens of ''

Corynebacterium diphtheriae ''Corynebacterium diphtheriae'' is the pathogenic bacterium that causes diphtheria. It is also known as the Klebs–Löffler bacillus, because it was discovered in 1884 by German bacteriologists Edwin Klebs (1834–1912) and Friedrich Löffl ...

'', the bacteria that causes diphtheria. It is used to test for toxigenicity of ''C. diphtheriae'' strains. The test uses

immunodiffusion Immunodiffusion is a diagnostic test which involves diffusion through a substance such as agar which is generally soft gel agar (2%) or agarose (2%), used for the detection of antibodies or antigen. The commonly known types are: :# Single diffusi ...

. A strip of filter paper impregnated with diphtheria antitoxin is buried just beneath the surface of a special agar plate before the

agar Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from ogonori (''Gracilaria'') and "tengusa" (''Gelidiaceae''). As found in nature, agar is ...

hardens. Strains to be tested are streaked with known positive and known negative toxigenic strains on the agar's surface in a line across the plate, and at a right angle to the antitoxin paper strip. After incubation for 24 hours at 37 degrees Celsius, plates are examined with transmitted light for the presence of fine

precipitin A precipitin is an antibody which can precipitate out of a solution upon antigen binding. Precipitin reaction The precipitin reaction provided the first quantitative assay for antibody. The precipitin reaction is based upon the interaction of anti ...

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. The test was characterized in 1949 by Hungarian-born British

microbiologist A microbiologist (from Ancient Greek, Greek ) is a scientist who studies microscopic life forms and processes. This includes study of the growth, interactions and characteristics of Microorganism, microscopic organisms such as bacteria, algae, f ...

Stephen Dyonis Elek (1914–1992). It provided an easier way to test the toxigenicity of ''C. diphtheriae'' specimens compared with previous tests. It also allowed an ''in vitro'' test to replace a clinical test on laboratory animals, helping with the "reduce" component of the three R's. Diphtheria was a major public health scourge, killing entire families with acute airborne pulmonary disease, before

diphtheria vaccine Diphtheria vaccine is a toxoid vaccine against diphtheria, an illness caused by '' Corynebacterium diphtheriae''. Its use has resulted in a more than 90% decrease in number of cases globally between 1980 and 2000. The first dose is recommended ...

brought it under control. At the time Elek developed this test, control of the disease was not yet secured in all regions of the world. Today its control is threatened by vaccine hesitancy.

References

Medical tests Diphtheria {{microbiology-stub