Klebsiella granulomatis is the etiologic agent of granuloma inguinale, or donovanosis, a sexually transmitted disease.
GENERAL CHARACTERISTICS
K. granulomatis is an encapsulated, pleomorphic, gram-negative bacillus that is usually observed in vacuoles in the cells of large mononuclear cells.
EPIDEMIOLOGY AND PATHOGENESIS
Granuloma inguinale is uncommon in the United States but is recognized as a major cause of genital ulcers in India, Papua New Guinea, the Caribbean, Australia, and parts of South America. The causative agent is sexually transmitted, although there is a possibility that it may be nonsexually transmitted as well. Infectivity of this bacillus must be low, because sexual partners of infected patients often do not become infected or require repeated expo sures to become infected.
SPECTRUM OF DISEASE
Granuloma inguinale is characterized by the presence of enlarged subcutaneous nodules that evolve to form beefy, erythematous, granulomatous, painless lesions that bleed easily. The lesions, which usually occur on the genitalia, have been mistaken for neoplasms. Patients often have inguinal lymphadenopathy.
LABORATORY DIAGNOSIS
The organism can be visualized in scrapings of lesions stained with Wright’s or Giemsa stain. Subsurface infected cells must be present; surface epithelium is not an adequate specimen. Groups of organisms are seen within mononuclear endothelial cells; this pathognomonic entity is known as a Donovan body, named after the physician who first visualized the organism in such a lesion. The organism stains as a blue rod with prominent polar granules, giving rise to a “safety pin” appearance, sur rounded by a large, pink capsule.
Cultivation in vitro is difficult, but it can be done using media containing some of the growth factors found in egg yolk. A medium described by Dienst has been used to culture K. granulomatis from aspirated bubo material. More recently, this agent was cultured in human monocytes from biopsies of genital ulcers of patients with donovanosis.
ANTIBIOTIC SUSCEPTIBILITY TESTING AND THERAPY
No antibiotic susceptibility testing is performed. Trimethoprim/sulfamethoxazole and doxycycline are the most effective drugs for the therapy of granuloma inguinale. Ciprofloxacin, azithromycin, or erythromycin (in pregnancy) also provides effective treatment for granuloma inguinale.
