Technique	ELEK TEST for DIPHTHERIA TOXIN ,(/,)/,(
Principle	The Elek test is an in vitro test to determine whether or not a strain of C. diptheriae is toxinogenic
Cautions
Method	Mix a tube of melted nutrient agar with 2 ml of sterile horse serum. Rotate the tube to mix the serum and agar. Do not shake the tube. Pour the mixture into a sterile Petri dish. Using lightly flamed forceps, lay the strip of anti-toxin impregnated filter paper across the centre of the Petri dish allowing it to sink beneath the agarsurface. Allow the agar to set, then lift one corner of the lid and let the plate dry for 30-45 min in the incubator. When dry inoculate with a toxinogenic strain of C. diptheriae by streaking a single line of inoculum across the plate and paper strip at right angles to the strip. Repeat this about 1 inch away from the C. diptheriae inoculum with a test strain. Incubate the plate for 24 hrs and observe the results. If toxin is produced by the test strain, it diffuses sideways from the streak. The antitoxin diffuses from the filter paper and where the toxin and the antitoxin meet a precipitate is formed. The control strain also will cause a precipitate to form which will coalesce with the precipitate of the test strain to form a line of identity
Results
Positive control
Negative control
Reagents
Reference