The immunodiffusion test used to detect toxigenic strains of Corynebacterium diphtheriae is called which test?

The immunodiffusion test used to detect toxigenic strains of Corynebacterium diphtheriae is called which test?

• A. D-test
• B. Elektest
• C. Hodge test
• D. Naglertest

Answer: (B)

Detecting whether Corynebacterium diphtheriae strains produce diphtheria toxin uses an immunodiffusion assay called the Elek test. In this test, a strip containing diphtheria antitoxin is placed in agar, and the bacterial isolate is streaked perpendicular to the strip. If the organism produces diphtheria toxin, the toxin diffuses into the agar and forms a toxin–antitoxin precipitin line where it meets the antibody in the strip. The appearance of these lines indicates toxigenicity, while their absence indicates non-toxigenic strains. Other tests listed are used for different purposes—inducible antibiotic resistance, carbapenemase production, or lecithinase activity—and do not assess diphtheria toxin production.

Detecting whether Corynebacterium diphtheriae strains produce diphtheria toxin uses an immunodiffusion assay called the Elek test. In this test, a strip containing diphtheria antitoxin is placed in agar, and the bacterial isolate is streaked perpendicular to the strip. If the organism produces diphtheria toxin, the toxin diffuses into the agar and forms a toxin–antitoxin precipitin line where it meets the antibody in the strip. The appearance of these lines indicates toxigenicity, while their absence indicates non-toxigenic strains. Other tests listed are used for different purposes—inducible antibiotic resistance, carbapenemase production, or lecithinase activity—and do not assess diphtheria toxin production.