Which statement correctly describes Shigella dysenteriae?

Which statement correctly describes Shigella dysenteriae?

• A. Lactose fermenter
• B. H2S positive
• C. Citrate utilizers
• D. H2S negative and non-lactose-fermenting

Answer: (D)

Shigella dysenteriae is a non-lactose-fermenting, hydrogen sulfide–negative enteric bacterium. On common diagnostic media like MacConkey agar, it does not ferment lactose, so colonies appear colorless or pale. In H2S tests (such as TSI slants), it does not produce hydrogen sulfide, so there’s no blackening. It also does not typically utilize citrate. Therefore, the description that fits best is H2S negative and non-lactose-fermenting. The other options point to features seen in lactose-fermenting organisms or H2S producers, which Shigella dysenteriae does not have.

Shigella dysenteriae is a non-lactose-fermenting, hydrogen sulfide–negative enteric bacterium. On common diagnostic media like MacConkey agar, it does not ferment lactose, so colonies appear colorless or pale. In H2S tests (such as TSI slants), it does not produce hydrogen sulfide, so there’s no blackening. It also does not typically utilize citrate. Therefore, the description that fits best is H2S negative and non-lactose-fermenting. The other options point to features seen in lactose-fermenting organisms or H2S producers, which Shigella dysenteriae does not have.