Burkholderia pseudomallei is a bacterium in the Proteobacteria division and in the Burkoholderiaceae family. It can cause the disease melioidosis in humans.
What is Burkholderia pseudomallei?
The pathogen Burkholderia pseudomallei belongs to the Gram-negative bacteria. Gram-negative bacteria can be stained red in what is known as Gram stain. In addition to a thin peptidoglycan layer made of the substance murein, Gram-negative bacteria also have a cell membrane on their outer envelope. Burkholderia pseudomallei is strictly aerobic. Aerobic bacteria require oxygen for their metabolism. The bacterium is rod-shaped and thus belongs to the rod-shaped bacteria. It lives saprophytically. Saprophytes are organisms that feed on dead organic matter. They break down these energy-containing substances and subsequently convert them into inorganic substances. Particularly in the case of bacteria, the transition from a saprophyte to a parasite is fluid. Burkholderia pseudomallei grows intracellularly and is oxidase positive. In the microbiological process of oxidase reaction, it is tested whether the corresponding bacterial strain possesses the enzyme cytochrome C oxidase. This information plays a decisive role in the choice of therapy, among other things. Burkholderia pseudomallei originates from the genus Burkholderia. However, this classification did not take place until the 1990s. Before that, the bacterium was already assigned to the groups Bacillus, Mycobacterium, Peifferella, Actinobacillus and Pseudomonas. Burkholderia pseudomallei has an average diameter of 0.6 μm and grows to about 5 μm long. It moves around with the help of flagella. Flagella are also known as flagella. They are thread-like structures that sit on the surface of the bacteria and are used for locomotion.
Occurrence, distribution and characteristics
Burkholderia pseudomallei is found in soil and water. Domestic and wild animals also serve as reservoirs. The bacterium is endemic to both northern Australia and southeast Asia. Serotypes are also distinguished based on the geographic areas. Serotype /ara+ is more commonly found in Southeast Asia. Serotype II/ara occurs preferentially in northern Australia. Infection with Burkholderia pseudomallei occurs mainly through direct contact with contaminated soil or contaminated water. In tropical countries, workers in rice fields frequently become infected with melioidosis. The pathogen enters the organism through the smallest skin lesions. However, infection can also occur via inhalation or oral intake. Infection from person to person is also possible via body fluids. Furthermore, there is a risk of infection in the laboratory through inhalation of infectious aerosols. Cases repeatedly appear in the news where the bacterium has escaped from laboratories. Most recently, this happened in 2014 in the U.S. state of Louisiana. There, four rhesus monkeys fell ill in an outdoor facility and a scientist was also infected. Burkholderia pseudomallei is considered a potential bioweapon and is on the bioweapon agent list.
Diseases and ailments
The bacterium Burkholderia pseudomallei causes the infectious disease melioidosis. This is also known as Whitmore’s disease or pseudorotz. The incubation period varies widely. It can be as short as two days or as long as several years. The course and symptoms of the disease also vary greatly. Many infections are completely asymptomatic. In other patients, a mild chronic disease develops. Still others react with an acute fulminant disease. After the pathogen has entered the body via a skin lesion, a small nodule often develops in the skin. The surrounding lymph vessels become inflamed (lymphangitis) and the lymph nodes also react (lymph node swelling). Patients have a fever and feel tired, listless and sick. This local infection can quickly spread to the whole body. In this case, it is then a generalized, septicemic course. In this life-threatening course, abscesses form all over the body. The lungs are also affected by abscess formation. Patients suffer from clouding of consciousness and severe shortness of breath. The respiratory rate is increased. If the pathogen has not entered the body through the skin but has been inhaled, pneumonia usually develops directly.A characteristic feature of melioidosis is pronounced cavern formation. Caverns are pathological cavities within the lungs. Gas exchange can no longer take place in these cavities, so that the functionality of the lung is severely restricted. Pleural effusion often develops in addition to pneumonia. In this case, fluid, in most cases inflammatory exudate, enters the pleural space. Compression of the lungs makes breathing even more difficult. In many cases, melioidosis progresses chronically and without fever. Abscesses form in various organs. Depending on the organ system affected, different symptoms may occur. Diabetics and people with a suppressed immune system are particularly at risk. Even if an infection does not show any symptoms for several years, the disease may manifest itself in the case of immunodeficiency. Antibiotics and chemotherapeutic agents in a high dosage are used to treat melioidosis. These are usually administered intravenously. After the acute symptoms have subsided, therapy must often be continued orally for several months. Abscesses caused by the disease are surgically removed. There is no effective prophylaxis against the bacterium Burkholderia pseudomallei. Anyone traveling in endemic areas should carefully clean and disinfect skin lesions. Burkholderia pseudomallei is sensitive to various disinfectants.
