Granuloma inguinale is caused by:
**Granuloma Inguinale**
**Core Concept**
Granuloma inguinale, also known as Donovanosis, is a chronic, sexually transmitted bacterial infection characterized by the formation of granulomatous lesions in the genital area. The causative agent is a gram-negative bacterium that belongs to the genus Klebsiella.
**Why the Correct Answer is Right**
The bacterium responsible for granuloma inguinale is Klebsiella granulomatis (previously known as Calymmatobacterium granulomatis). This bacterium infects the skin and mucous membranes, leading to the formation of granulomas that contain Donovan bodies, which are characteristic inclusions found within macrophages. The infection is transmitted through direct contact with an infected person's lesion or through sexual contact.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the bacterium that causes granuloma inguinale is not Chlamydia trachomatis, which is a different sexually transmitted pathogen that causes chlamydia.
**Option B:** This option is incorrect because Haemophilus ducreyi is the causative agent of chancroid, a different sexually transmitted infection that presents with painful genital ulcers.
**Option C:** This option is incorrect because Treponema pallidum is the bacterium that causes syphilis, another sexually transmitted infection that has distinct clinical manifestations and diagnostic features.
**Clinical Pearl / High-Yield Fact**
Donovan bodies, the characteristic inclusions found within macrophages in granuloma inguinale, are named after the Australian pathologist Thomas Donovan, who first described them in 1905. Identifying Donovan bodies on histopathology is crucial for diagnosing granuloma inguinale.
**Correct Answer: C. Treponema pallidum**