MICROBIOLOGY NOTES

 

   

Donovanosis (granuloma inguinale)

Donovanosis is a sexually transmitted disease caused by Calymmatobacterium granulomatis, a gram-negative intracellular bacillus found in mononuclear cells. This bacterium is now reclassified as Klebsiella granulomatis. The bacterium was formerly known as Donovania granulomatis, named after its discoverer; Charles Donovan. The disease, also called Granuloma inguinale is more common in some tropical and subtropical countries. Donovanosis is a chronic, progressive, granulomatous disease involving skin and subcutaneous tissue of genital, inguinal and anal region.

Etiology: 
C.granulomatis is a capsulated gram negative bacillus which is non-motile, pleomorphic, non-sporing and displays bipolar staining. The safety pin appearance is due to single or bipolar condensation of chromatin. On staining with Wright's stain it appears as blue bacillus with pink capsule. The name Calymmatobacterium has been derived from the Greek word kalymna, meaning veil or hood that represent its distinct capsule. 

Mode of transmission: 
Sexual contact

Incubation period: 
One to two weeks

Signs and symptoms: 
Sites of infection are the penis, scrotum, groin, and thighs in men; the vulva, vagina, and perineum in women; the anus and buttocks in homosexual men. The initial lesion is a painless, red nodule that slowly enlarges as an elevated, malodorous, granulating ulcerated plaque. The single or multiple subcutaneous nodules erodes the skin to produce clear, sharply defined painless ulcer. "Pseudobuboes" may form that break down to form inguinal ulcers.

In contrast to lymphogranuloma venerum, lymphadenopathy is absent. The disease spreads by extension and autoinoculation. The ulcers may persist for months and may extend into the inguinal region or may cover the genitalia. Healing is slow with scarring. Lesions may sometimes be seen on non-genital parts such as mouth, lips, throat and face.

Secondary infection is common and can cause gross tissue destruction. Pseudoelephantiasis of external genitilia can rarely occur. Hematogenous dissemination to bones, joints, or liver may occur occasionally. 

Laboratory diagnosis: 

  • Specimen collected: Before obtaining any specimen the lesion must be swabbed with sterile saline. Scrapings from the edge or extending border of the ulcer are collected. If scrapings are non-productive, punch biopsy is collected from the edge of the lesion.

  • Microscopy: Impression smears from biopsy specimens stained with Wright or Giemsa stain show clusters of encapsulated bacilli in the cytoplasm of mononuclear cells. These aggregates are called Donovan bodies and are considered diagnostic.

  • Culture: It does not grow on ordinary culture medium but can be cultivated in yolk sac of embryonated egg. Coagulated egg yolk slants or a semi-defined medium containing lactalbumin hydrolysate has been used.

Treatment: 
Tetracyclines, macrolides, and trimethoprim-sulfamethoxazole have been used most successfully, but aminoglycosides, quinolones, and chloramphenicol have also been effective. 


Print This Page

   Last edited in March 2008