Tellurite reduction is used for presumptive identification of which organism?

Tellurite reduction is used for presumptive identification of which organism?

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

Answer: (B)

Tellurite reduction is used as a presumptive test because Corynebacterium diphtheriae can reduce tellurite ions in potassium tellurite-containing media, producing dark, often black colonies. This visible change on the selective medium is a distinctive clue that helps screen for C. diphtheriae in clinical specimens. Other organisms listed do not typically form black colonies on tellurite media, so they won’t give the same characteristic appearance, making this reaction a practical first-step identification for diphtheria before confirmatory testing.

Tellurite reduction is used as a presumptive test because Corynebacterium diphtheriae can reduce tellurite ions in potassium tellurite-containing media, producing dark, often black colonies. This visible change on the selective medium is a distinctive clue that helps screen for C. diphtheriae in clinical specimens. Other organisms listed do not typically form black colonies on tellurite media, so they won’t give the same characteristic appearance, making this reaction a practical first-step identification for diphtheria before confirmatory testing.