Chancroid is caused by: September 2005
**Core Concept**
Chancroid is a sexually transmitted infection characterized by painful genital ulcers. The underlying cause of this condition is a bacterial infection. **Haemophilus ducreyi** is the bacterium responsible for chancroid.
**Why the Correct Answer is Right**
**Haemophilus ducreyi** causes chancroid by infecting the skin and mucous membranes, leading to the formation of painful ulcers. This bacterium is typically spread through sexual contact with an infected person. The infection manifests as one or more painful ulcers or open sores in the genital area.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the cause is not specified.
**Option B:** Incorrect as it is not related to chancroid.
**Option C:** Incorrect as it is not the bacterium that causes chancroid.
**Option D:** Incorrect as it is not **Haemophilus ducreyi**.
**Clinical Pearl / High-Yield Fact**
Chancroid is an important diagnosis to consider in patients with painful genital ulcers, as it can be distinguished from other causes of genital ulcers, such as syphilis and herpes simplex virus infection.
**Correct Answer:** D. Haemophilus ducreyi.