INTRACELLULAR SURVIVAL OF BURKHOLDERIA-PSEUDOMALLEI

Burkholderia pseudomallei is the causative agent of melioidosis, a dis ease being increasingly recognized as an important cause of morbidity and mortality in many regions of the world. Several features of melioi dosis suggest that B. pseudomallei is a facultative intracellular path ogen. This study was designed to assess the ability of B. pseudomallei to invade and survive in eukaryotic cells. We have shown that B. pseu domallei has the capacity to invade cultured cell lines, including HeL a, CHO, A549, and Vero cells. We have demonstrated intracellular survi val of B. pseudomallei in professional phagocytic cells, including rat alveolar macrophages, B. pseudomallei was localized inside vacuoles i n human monocyte-like U937 cells, a histiocytic lymphoma cell line wit h phagocytic properties. Additionally, electron microscopic visualizat ion of B. pseudomallei-infected HeLa cells and polymorphonuclear leuko cytes confirmed the presence of intracellular bacteria within membrane -bound vacuoles. B. pseudomallei was found to be resistant to the cati onic peptide protamine and to purified human defensin HNP-1.