All of the following proteus species forms indole EXCEPT: September 2004
**Core Concept**
Proteus species are Gram-negative bacteria that can be identified by their ability to produce various enzymes, including indole. Indole production is a characteristic feature of some Proteus species, which is detected using the Ehrlich's reagent test.
**Why the Correct Answer is Right**
Proteus mirabilis, Proteus penneri, and Proteus vulgaris are known to produce indole due to the action of the enzyme tryptophanase. Tryptophanase breaks down tryptophan to form indole, pyruvate, and ammonia. This reaction is specific to these Proteus species, making indole production a useful diagnostic tool.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not specify the Proteus species. However, if we assume it is Proteus mirabilis, it still forms indole.
**Option B:** Incorrect because there is no Proteus species commonly known as "Proteus B". However, if we assume it is another species, it should be mentioned specifically.
**Option C:** Incorrect because Proteus hauseri is known to produce indole, similar to other Proteus species.
**Clinical Pearl / High-Yield Fact**
It is essential to note that indole production is not a foolproof method for identifying Proteus species, as some strains may not produce indole or may have variable indole production. Therefore, identification of Proteus species should be confirmed using multiple tests, including biochemical and molecular methods.
**Correct Answer: D.**