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.
The clinical manifestation of the disease can range from simple skin changes such as abscesses or ulcerations to severe organ problems. The commonest organs affected are liver, spleen, lungs, prostate, and kidneys. Among the most common features are bacteremia (in 40 to 60% of cases), pneumonia (50%), and septic shock (20%). People with only pneumonia may have a prominent cough with sputum and shortness of breath. However, those with septic shock together with pneumonia may have minimal coughing. Results of a chest X-ray can range from diffuse nodular infiltrates in those with septic shock to progressive consolidation located most commonly in the upper lobes for those with pneumonia only. Pleural effusion and empyema are more common for melioidosis affecting lower lobes of the lungs. In 10% of cases, people develop secondary pneumonia caused by other bacteria after the primary infection. In northern Australia, 60% of the infected children presented with only skin lesions, while 20% presented with pneumonia.Depending on the course of infection, other severe manifestations develop. Approximately 1 to 5% of those infected develop inflammation of the brain and brain covering or brain abscess; 14 to 28% develop pyelonephritis, kidney abscess or prostatic abscesses; 0 to 30% develop neck or salivary gland abscesses; 10 to 33% develop liver, spleen, or paraintestinal abscesses; and 4 to 14% develop septic arthritis and osteomyelitis. Rare manifestations include lymph node disease resembling tuberculosis, mediastinal masses, pericardial effusion, mycotic aneurysm, and inflammation of the pancreas.