Tellurite reduction is used for the presumptive identification of which organism?

Tellurite reduction is used for the presumptive identification of which organism?

• A. Bacillus anthracis
• B. Corynebacterium diphtheriae
• C. Erysipelothrix rhusiopathiae
• D. Staphylococcus saprophyticus

Answer: (B)

Tellurite reduction on tellurite-containing media is a classic screen for Corynebacterium diphtheriae. This organism reduces the tellurite in the medium to metallic tellurium, producing distinctive black colonies (often with a brown halo on media like Tinsdale agar). That visible reaction makes it a rapid presumptive clue to diphtheria, prompting confirmatory tests for toxin production or molecular detection. The other organisms listed do not characteristically form the same black colonies on tellurite media, so tellurite reduction is not used to presumptively identify them.

Tellurite reduction on tellurite-containing media is a classic screen for Corynebacterium diphtheriae. This organism reduces the tellurite in the medium to metallic tellurium, producing distinctive black colonies (often with a brown halo on media like Tinsdale agar). That visible reaction makes it a rapid presumptive clue to diphtheria, prompting confirmatory tests for toxin production or molecular detection. The other organisms listed do not characteristically form the same black colonies on tellurite media, so tellurite reduction is not used to presumptively identify them.