Klebsiella granulomatis is an unflagellated, Gram-negative, rod-shaped bacterium of the Enterobacteriaceae family. It lives facultatively anaerobically in the cytoplasm of large, mononuclear cells and is the causative agent of the venereal disease donovanosis. The bacterium does not form spores and therefore depends on direct human-to-human transmission, usually through sexual intercourse, for longer-term survival.
What is Klebsiella granulomatis?
Klebsiella granulomatis is the causative agent of the venereal disease donovanosis, also called granuloma inguinale. The bacterium belongs to the enterobacteria family because most species are found in the digestive tract. The gram-negative bacterium is unflagellated and not capable of independent locomotion. It lives facultatively anaerobically in the cytoplasm of large, mononuclear cells, occasionally intracellularly in certain leukocytes with polymorphic nuclei. Its mode of appearance is pleomorphic, meaning that it can assume other forms besides rod form. For example, immature bacteria can assume a small spherical (coccoid) shape. Mature bacteria of the Klebsiella granulomatis species can form elliptical capsules, but also occur as cocci or diplococci, depending on the environmental conditions, in which two cocci join together like a pair at a time. The bacterium does not form permanent forms or spores, so it relies on direct host-to-host transmission for its longer-term survival.
Occurrence, distribution, and characteristics
Klebsiella granulomatis is the causative agent of the sexually transmitted disease donovanosis, which is classified as an STD. STDs are subject to anonymous reporting in Germany. The disease has an endemic prevalence in some developing countries, as there is often no medical care available or those affected cannot afford the necessary drug treatment. Major areas of dementia were found in regions and countries such as India, Brazil, South Africa and Papua New Guinea. In Australia, the disease was particularly rampant among Aborigines. Education and better medical care have now greatly curbed infectious donovanosis. The bacterium can only be transmitted through intensive skin contact. By far the most common way of infection is therefore through sexual intercourse. The bacteria predominantly colonize tissues of the external genital organs and the anal area. Several days to several weeks after infection, painless ulcers appear, which can be confused with ulcers as they are also typical for the venereal disease syphilis. Typical distinguishing features of ulcerations caused by Klebsiella granulomatis from syphilitic ulcers are their painlessness and their rolled edge. Another distinguishing feature is that Klebsiella granulomatis infections usually do not involve the lymph nodes, thus do not show any swelling or tenderness. In addition, microscopic detection using smears or biopsies from the margins of the lesions can provide certainty. The microscopic image typically shows so-called Donovan corpuscles in the cells that were previously stained according to Wright-Giemsa. The corpuscles are clearly visible under the light microscope after staining as oval structures intracellularly in macrophages and histiocytes. The bacterium cannot be grown on culture media. Klebsiella granulomatis responds well to certain antibiotics. Usually, the bacteria are treated with macrolide antibiotics or tetracyclines. Macrolide antibiotics are usually well tolerated and have a bacteriostatic effect on many bacterial species by effectively inhibiting their protein synthesis. They are also commonly used to treat gonorrhea and to control chlamydial infections. The group of tetracyclines have broad bacteriostatic activity against many gram-negative and gram-positive bacteria. However, tetracyclines have strong calcium-binding properties that lead to side effects and should be considered. Treatment of donovanosis is also common with cotrimoxazole. This is a combination of the two antibiotics trimethoprim and sulfamethoxazole with very broad antibiotic activity. When combating Klebsiella granulomatis, it should be noted that the bacterium – like many other gram-negative bacteria – is resistant to beta-lactam antibiotics.
Diseases and ailments
If left untreated, the venereal disease granuloma inguinale can lead to tissue destruction of the external genital organs and the anal area. Not only is this associated with partially disfiguring and mutilating effects, but the progressive tissue destruction with marked hemorrhage increases the risk of secondary microbial infection. Due to the existing lesions, the skin largely loses its ability to prevent the penetration of microorganisms. The hemorrhages that take place allow certain pathogenic germs to enter directly into the bloodstream. For example, donovanosis is associated with an increased risk of HIV infection because HIV pathogens have “easier game” for infection. At existing hemorrhages on the genitals, the skin barrier that normally has to be overcome is severely weakened or completely absent. AIDS viruses are therefore shown to be significantly more infectious in individuals who already have advanced Klebsiella granulomatis than in individuals who do not have this pre-existing condition. Donovanosis is relatively effectively treatable with certain antibiotics, but there is a risk of recurrent disease for up to 18 months after successful treatment. Sexual partners who had intercourse with the infected person up to 40 days before the first symptoms appeared also carry the risk of infection. Infected individuals should also abstain from all sexual intercourse during treatment with appropriate antibiotics until the disease is completely healed. This will ensure that they do not infect others during this time.
