When MNGCs lyse, they form plaques (a central clear area with a ring of fused cells) that provide shelter for the bacteria for further replication or latent infection. This same process in infected neurons can allow bacteria to travel through nerve roots in the spinal cord and brain, leading to inflammation of the brain and spinal cord. In addition to spreading from cell to cell, the bacteria can also spread through the bloodstream, causing sepsis. The bacteria can survive in antigen-presenting cells and dendritic cells. Thus, these cells act as vehicles that transport the bacteria into the lymphatic system, causing widespread dissemination of the bacteria in the human body.While B. pseudomallei can survive in phagocytic cells, these cells can kill B. pseudomallei by several mechanisms. Macrophages activated by interferon gamma (IFN) have improved the killing of B. pseudomallei via the production of inducible nitric oxide synthase. Acidification of the endosome and degradation of the bacteria is also possible, however, the bacterial capsule and LPS makes B. pseudomallei resistant to lysosomal degradation. Once B. pseudomallei escapes into the host cytosol it can be recognized by pattern recognition receptors such as NOD-like receptors, triggering the formation of the inflammasome and activation of caspase 1, which induces death of the host cell by pyroptosis and further activation of the immune system. Several systemic host defenses also contribute to the immune response.
There is little evidence in supporting the use of melioidosis prophylaxis in humans. The antibiotic co-trimoxazole is used as a preventative only for individuals at high risk for getting the disease after being exposed to the bacteria in laboratory settings. One study conducted in 2018 determined that the drug could be useful in preventing melioidosis in high-risk renal failure patients undergoing haemodylysis. There is no approved vaccine for melioidosis.Approximately 165,000 people are infected by melioidosis per year, resulting in about 89,000 deaths, based on a mathematical model published in 2016. Diabetes is a major risk factor for melioidosis; over half of melioidosis cases are in people with diabetes. Increased rainfall and severe weather events such as thunderstorm are associated with an increased number of melioidosis cases in endemic areas. Signs and symptoms
Acute
Most people exposed to B. pseudomallei experience no symptoms. The mean incubation period of acute melioidosis is 9 days (range 1–21 days). Nevertheless, symptoms of melioidosis can appear in 24 hours for those who experienced near drowning in water. Those affected present with symptoms of sepsis (predominantly fever) with or without pneumonia, or localised abscess or other focus of infection. The presence of non-specific signs and symptoms has caused melioidosis to be nicknamed "the great mimicker".Diabetes mellitus is one of the most important risk factors in developing melioidosis. The disease should be considered in anyone who has spent time in endemic areas who develops a fever, pneumonia, or abscesses in their liver, spleen, prostate, or parotid gland.