Biochemical Test of Klebsiella granulomatis
Klebsiella granulomatis is a gram-negative, rod-shaped bacterium that causes a chronic and progressive infection of the skin and mucous membranes called granuloma inguinale or donovanosis. This infection is characterized by the formation of painless, beefy-red ulcers that can bleed and spread to other areas of the body. The disease is mainly transmitted through sexual contact, but can also occur through non-sexual contact with infected tissues or fomites. Klebsiella granulomatis is endemic in tropical and subtropical regions of the world, especially in Africa, India, Southeast Asia, Australia and Latin America. The incidence of the disease has declined in recent years due to improved hygiene and antibiotic therapy, but it remains a public health problem in some areas where access to diagnosis and treatment is limited.
Klebsiella granulomatis was first described in 1905 by Charles Donovan, who observed intracellular bacteria in tissue samples from patients with granuloma inguinale. The bacterium was initially classified as a member of the genus Calymmatobacterium, but later reclassified as Klebsiella based on its genetic and biochemical similarities with other Klebsiella species. However, Klebsiella granulomatis differs from other Klebsiella species in several aspects, such as its inability to grow on standard culture media, its unique morphology and antigenic properties, and its pathogenicity and virulence factors. Therefore, some researchers have proposed to assign Klebsiella granulomatis to a separate genus or species within the Klebsiella group.
The diagnosis of granuloma inguinale is based on the clinical presentation of the lesions and the detection of intracellular bacteria in tissue smears or biopsies stained with Wright-Giemsa or silver nitrate. The definitive identification of Klebsiella granulomatis requires molecular techniques such as polymerase chain reaction (PCR) or DNA hybridization, which are not widely available in resource-limited settings. The treatment of granuloma inguinale consists of prolonged courses of antibiotics such as azithromycin, doxycycline, ciprofloxacin or trimethoprim-sulfamethoxazole. The prognosis of the disease depends on the extent and duration of the infection, the presence of complications such as secondary infections or malignancies, and the response to therapy. Prevention of granuloma inguinale requires education and awareness about the disease, promotion of safe sexual practices and condom use, and early detection and treatment of cases and contacts.
This image shows a case of granuloma inguinale (donovanosis) in a conventional Pap test. Granuloma inguinale is a chronic ulcerative disease of the genital and perineal regions caused by Klebsiella granulomatis, a gram-negative intracellular bacterium. The Pap test is a screening method for cervical cancer that involves scraping cells from the cervix and examining them under a microscope. In this image, the Pap smear shows numerous large mononuclear cells with intracytoplasmic inclusions that contain the bacteria. These inclusions are called Donovan bodies and are diagnostic of granuloma inguinale. The disease is rare in developed countries but endemic in some tropical and subtropical regions. It can be treated with antibiotics but may cause scarring and deformity if left untreated. Granuloma inguinale is also a risk factor for HIV transmission due to the presence of ulcers and inflammation.
This image shows a case of granuloma inguinale (donovanosis), a chronic ulcerative disease of the genital and perineal regions caused by Klebsiella granulomatis. The image is from a conventional Pap test, which is a screening method for cervical cancer. The Pap test can also detect other infections and inflammatory conditions of the cervix, such as granuloma inguinale.
The image shows several large, intracellular, rod-shaped bacteria with bipolar staining, also known as Donovan bodies. These are the characteristic features of Klebsiella granulomatis infection. The bacteria are usually found within the cytoplasm of histiocytes (macrophages) or endothelial cells. The infected cells may form clusters or granulomas, which can erode the surrounding tissue and cause ulceration.
The diagnosis of granuloma inguinale is based on the clinical presentation and the identification of Donovan bodies in tissue samples or smears. The disease can be treated with antibiotics, such as azithromycin or doxycycline. However, it is important to prevent the spread of the infection by practicing safe sex and seeking medical attention if any symptoms occur.
Klebsiella granulomatis is a rod-shaped, gram-negative bacterium that belongs to the genus Klebsiella and the family Enterobacteriaceae. It is predominantly pleomorphic, meaning it can be found in a variety of shapes and sizes such as coccoid, diplococci, straight rods, ovoid, or elliptical. It measures about 1 to 2 μm by 0.5 to 0.7 μm in size .
Klebsiella granulomatis is an encapsulated bacterium that has a clearly defined capsule and no flagella. However, it may have small surface projections resembling pili or fimbriae. It also has electron-dense granules in the cell periphery that may be related to bacteriophage infection.
Klebsiella granulomatis can be found in vacuoles in the cytoplasm of large mononuclear cells . The bacteria are frequently described as having bipolar densities that give these “Donovan bodies” the appearance of closed safety pins . The bacteria appear to multiply within these cells and are subsequently released to infect others after the rupture of mature intracytoplasmic vacuoles.
Klebsiella granulomatis is a stationary aerobic bacillus that can grow in oxygen-rich environments. It has biochemical properties such as catalase positive, phenylalanine negative and citrate positive with hydrolysis in urea . Among its virulence factors are its capsule, endotoxins, siderophores, antimicrobial resistance and antigenic phase variation.
Klebsiella granulomatis is known to cause the sexually transmitted disease granuloma inguinale (or donovanosis), which is characterized by ulcerating lesions of the genitalia and anus . The incubation period lasts around 50 days, but may vary between 1 and 12 weeks. The disease is rare in western countries but is common in parts of Africa, South America, Papua New Guinea, India and the Caribbean .
Klebsiella granulomatis is a gram-negative, rod-shaped bacterium that causes granuloma inguinale (donovanosis), a chronic and progressive genital ulcer disease. It is also known as Calymmatobacterium granulomatis or Donovania granulomatis. The bacterium is difficult to culture and identify by conventional methods, so it is often diagnosed by histopathological examination of tissue biopsies or smears.
Some of the properties of Klebsiella granulomatis are:
- It is an obligate intracellular parasite that resides within vacuoles of macrophages and endothelial cells in the granulation tissue of the lesions.
- It produces distinctive intracellular inclusion bodies called Donovan bodies, which are oval or rod-shaped structures with bipolar staining and a clear halo around them. Donovan bodies can be seen in Wright-Giemsa or silver-stained smears under a light microscope.
- It is non-motile, non-spore-forming, and does not form capsules or biofilms.
- It is oxidase-negative and urease-negative, but positive for nitrate reduction and indole production.
- It does not grow on MacConkey agar or blood agar, but can grow on chocolate agar or Thayer-Martin agar with increased CO2 and humidity.
- It is susceptible to aminoglycosides, tetracyclines, macrolides, and sulfonamides, but resistant to penicillins and cephalosporins.
Catalase is an enzyme that breaks down hydrogen peroxide into water and oxygen. This reaction can be used to differentiate between bacteria that produce catalase and those that do not. Catalase-positive bacteria can produce bubbles when exposed to hydrogen peroxide, while catalase-negative bacteria do not.
Klebsiella granulomatis is a catalase-negative bacterium. This means that it does not produce the enzyme catalase and cannot break down hydrogen peroxide. Therefore, when a drop of hydrogen peroxide is added to a culture of Klebsiella granulomatis, no bubbles are observed.
The catalase test is a simple and rapid method to identify Klebsiella granulomatis from other Klebsiella species, which are catalase-positive. The test can also help to distinguish Klebsiella granulomatis from other bacteria that cause similar infections, such as Haemophilus ducreyi and Calymmatobacterium granulomatis, which are also catalase-negative.
The catalase test is performed by using a sterile loop or swab to transfer a small amount of bacterial growth from a culture plate or a clinical specimen to a clean glass slide. A drop of 3% hydrogen peroxide solution is then added to the slide and the presence or absence of bubbles is observed within 10 seconds. A positive result is indicated by the formation of bubbles, while a negative result is indicated by no bubbles.
The catalase test should be performed with caution, as some bacteria may produce false-negative results due to low catalase activity or inhibition by other substances. Therefore, the test should be confirmed by other biochemical tests or molecular methods for accurate identification of Klebsiella granulomatis.
Klebsiella granulomatis is a facultative anaerobe, which means it can grow in the presence or absence of oxygen. It can use different substrates as sources of carbon and energy, such as glucose, lactose, mannitol, and sucrose. Fermentation is the process of breaking down these substrates to produce acids, gases, and other by-products.
One way to identify Klebsiella granulomatis is to perform a fermentation test using different media that contain specific substrates and indicators. For example, phenol red broth is a medium that contains glucose and a pH indicator called phenol red. If Klebsiella granulomatis ferments glucose, it will produce acid and lower the pH of the medium, turning it from red to yellow. Phenol red broth can also contain other sugars, such as lactose or sucrose, to test for the ability of Klebsiella granulomatis to ferment them.
Another example of a fermentation test is the methyl red test, which measures the production of mixed acids from glucose fermentation. Klebsiella granulomatis produces a large amount of mixed acids, such as acetic acid, lactic acid, and formic acid, when it ferments glucose. These acids lower the pH of the medium below 4.4. When methyl red, a pH indicator, is added to the medium, it turns red if the pH is below 4.4, indicating a positive result for Klebsiella granulomatis.
A third example of a fermentation test is the Voges-Proskauer test, which detects the production of 2,3-butanediol from glucose fermentation. Klebsiella granulomatis produces a small amount of 2,3-butanediol, which is not acidic and does not affect the pH of the medium. However, 2,3-butanediol can be converted to acetoin by oxidation. When Barritt`s reagents A and B are added to the medium, they react with acetoin and form a red complex, indicating a positive result for Klebsiella granulomatis.
These are some of the fermentation tests that can be used to identify Klebsiella granulomatis based on its metabolic capabilities. Fermentation tests are useful for distinguishing Klebsiella granulomatis from other bacteria that have similar morphology and staining properties.
Klebsiella granulomatis is a bacterium that causes granuloma inguinale, a chronic ulcerative disease of the genital and inguinal regions. The bacterium can be identified by its biochemical and enzymatic reactions, which are different from other Klebsiella species.
One of the most distinctive features of Klebsiella granulomatis is its inability to produce urease, an enzyme that hydrolyzes urea to ammonia and carbon dioxide. This contrasts with other Klebsiella species, which are usually urease-positive. The urease test can be performed by inoculating a urea broth or agar with the bacterium and observing the color change after 24 hours. A positive result is indicated by a pink or red color, while a negative result is indicated by no color change or a yellow color.
Another enzymatic reaction that can help differentiate Klebsiella granulomatis from other Klebsiella species is the nitrate reduction test. This test detects the ability of the bacterium to reduce nitrate to nitrite or nitrogen gas. The test can be performed by adding nitrate reagents to a tube containing the bacterium and observing the color change. A positive result is indicated by a red color, while a negative result is indicated by no color change. Klebsiella granulomatis is usually nitrate-negative, while other Klebsiella species are usually nitrate-positive.
Other enzymatic reactions that can be used to identify Klebsiella granulomatis include:
- Indole test: This test detects the ability of the bacterium to produce indole from tryptophan. The test can be performed by adding Kovac`s reagent to a tube containing the bacterium and observing the color change. A positive result is indicated by a red ring at the top of the tube, while a negative result is indicated by no color change or a yellow ring. Klebsiella granulomatis is usually indole-negative, while other Klebsiella species are usually indole-positive.
- Methyl red test: This test detects the ability of the bacterium to produce acid from glucose fermentation. The test can be performed by adding methyl red indicator to a tube containing the bacterium and observing the color change. A positive result is indicated by a red color, while a negative result is indicated by no color change or a yellow color. Klebsiella granulomatis is usually methyl red-negative, while other Klebsiella species are usually methyl red-positive.
- Voges-Proskauer test: This test detects the ability of the bacterium to produce acetoin from glucose fermentation. The test can be performed by adding VP reagents to a tube containing the bacterium and observing the color change. A positive result is indicated by a red color, while a negative result is indicated by no color change or a brown color. Klebsiella granulomatis is usually VP-negative, while other Klebsiella species are usually VP-positive.
By performing these enzymatic reactions, Klebsiella granulomatis can be distinguished from other Klebsiella species and confirmed as the causative agent of granuloma inguinale.
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