Melioidosis is an infectious disease caused by a gram-negative bacterium called Burkholderia pseudomallei. Most people exposed to B. pseudomallei experience no symptoms; however, those who do experience symptoms have signs and symptoms that range from mild such as fever and skin changes, to severe with pneumonia, abscesses, and septic shock that could cause death. Approximately 10% of people with melioidosis develop symptoms that last longer than two months, termed "chronic melioidosis".Humans are infected with B. pseudomallei by contact with contaminated soil or water. The bacteria enter the body through wounds, inhalation, or ingestion. Person-to-person or animal-to-human transmission is extremely rare. The infection is constantly present in Southeast Asia particularly in northeast Thailand and northern Australia. In temperate countries such as Europe and the United States, melioidosis cases are usually imported from countries where melioidosis is endemic. The signs and symptoms of melioidosis resemble tuberculosis and misdiagnosis is common. Diagnosis is usually confirmed by the growth of B. pseudomallei from an infected persons blood or other bodily fluid such as pus, sputum, and urine. Those with melioidosis are treated first with an "intensive phase" course of intravenous antibiotics (most commonly ceftazidime) followed by a several-months treatment course of co-trimoxazole. In countries with the advanced healthcare system, approximately 10% of people with melioidosis die from the disease. In less developed countries, the death rate could reach 40%.Efforts to prevent melioidosis include: wearing protective gear while handling contaminated water or soil, practising hand hygiene, drinking boiled water, and avoiding direct contact with soil, water, or heavy rain.
However, the site of bacteria during latent infection and the mechanism by which they avoid immune recognition for years are both unclear. Amongst mechanisms suggested are: residing in the nucleus of the cell to prevent being digested, entering a stage of slower growth, antibiotic resistance, and genetic adaption to the host environment. Granulomas (containing neutrophils, macrophages, lymphocytes, and multinucleated giant cells) formed at the infection site in melioidosis have been associated with latent infection in humans. Diagnosis
Culture
Bacterial culture has 60% sensitivity in diagnosing melioidosis. B. pseudomallei is never part of human flora. Therefore, any growth of the bacteria is diagnostic of melioidosis. Other samples such as throat, rectal swabs, pus from abscesses, and sputum can also be used for culture. However, culture from CSF is difficult because in one case series, only 29% of the neuromelioidosis cases are culture positive. When bacteria do not grow from people strongly suspected of having melioidosis, repeated cultures should be taken as subsequent cultures can become positive. B. pseudomallei can be grown on any blood agar, MacConkey agar, and agar containing antibiotics such as Ashdowns medium (containing gentamicin), and Ashdowns broth (containing colistin) for better isolation of B. pseudomallei from other types of bacteria. Agar plates for melioidosis should be incubated at 37 °C (98.6 °F) in air  and inspected daily for four days. On the agar plates, B. pseudomallei forms creamy, non-haemolytic, colonies after 2 days of incubation. After 4 days of incubation, colonies appear dry and wrinkled.