Growth and cultural characteristics of Calymmatobacterium granulomatis--the aetiological agent of granuloma inguinale (Donovanosis).

ABSTRACT

Granuloma inguinale is a chronic destructive granulomatous disease of the genitalia. The clinical diagnosis is often unreliable and the definitive diagnosis is based on the visualisation of 'Donovan bodies' in tissue smears or biopsy specimens. The organism implicated in its aetiology, Calymmatobacterium granulomatis, was reported to have been cultured > 30 years ago, but little is known about the organism because of its fastidious nature and the difficulty in culturing it. Twenty-two biopsy specimens from female patients with clinical and laboratory-confirmed granuloma inguinale were treated with amikacin 10 mg/L and inoculated in a monocyte co-culture system with peripheral blood mononuclear cells (PBMC) from a single donor and autologous sera. The method was subsequently modified by pretreatment of specimens with vancomycin 5 mg/L and metronidazole 10 mg/L in addition to amikacin 10 mg/L for the purpose of decontamination, pooled blood donor PBMC and by the use of heat-inactivated fetal calf serum instead of autologous serum for culture. This modified method was used to culture additional biopsy specimens and genital ulcer scrapings from female and male patients, respectively. All monocyte co-cultures were examined by a rapid Giemsa (RapiDiff) stain and by an indirect immunofluorescence test with immune sera. Representative cultures were examined by transmission electron microscopy. C. granulomatis was successfully isolated in pure culture by the monocyte co-culture system from four biopsy specimens and 14 genital ulcer scrapings. The cultured organisms were visible both intra- and extra-cellularly and were extremely pleomorphic, with characteristic single and biopolar condensation. The numbers of the organisms increased after each passage. All positive cultures showed bright fluorescence when tested with immune sera. Transmission electron microscopy of the cultured bacteria demonstrated a typical gram-negative cell wall consisting of an outer membrane, middle electron opaque layer and an inner plasma membrane. The capsule was thick and electron dense. Numerous electron dense granules were present within the cytoplasm.