The histopathology of human melioidosis

Abstract

We examined human tissues infected by Burkholderia (Pseudomonas) pseudomallei which is endemic in Malaysia to study the types of inflammation invoked, and to look for histopathological clues to its diagnosis. The lesions which varied from acute to chronic granulomatous inflammation were not tissue-specific. In five autopsy cases, the inflammation was usually a focal or diffuse, acute necrotising inflammation with varying numbers of neutrophils, macrophages, lymphocytes and ‘giant cells’. The ‘giant cells’ probably represent giant macrophages with phagocytosed leukocytes. There were numerous gram-negative, non-acid-fast, intra- and extracellular bacilli, occurring either singly or in chains. Intracellular bacteria within macrophages and ‘giant cells’ were so numerous as to resemble globi. This feature has not been previously reported and may be a useful diagnostic clue in melioidosis. In 14 surgical cases biopsies showed acute inflammatory lesions that appeared no different from acute inflammation due to other causes. In many biopsies, however, the inflammation was either an acute-on-chronic inflammation with a focal granulomatous component, or was purely granulomatous in character. Bacilli were difficult to demonstrate in surgical biopsies even with the gram strain.