Objective       To establish an infection model of A549 cells by Burkholderia pseudomallei in vitro to study its pathogenesis.       Methods      The purpose of this study was to optimize the methods in infection of A549 cells by Burkholderia pseudomallei

such as multiplicity of infection (MOI) and incubation time. The number of intracellular bacteria and the formation of multinuclear giant cells (MNGCs) were visualized by Giemsa staining

live-cell digital video gallery

immunofluorescence assay and transmission electron microscopy. Furthermore

the expression of inflammatory cytokines

interleukin (IL)-8 and tumor necrosis factor (TNF)-α were detected.       Results       Monolayers of A549 cells were co-incubated with Burkholderia pseudomallei (MOI=100∶1) and centrifugated for 5 min at 170×g. At 1 hour of post-infection

the extracellular bacteria were killed by the addition of 250 μg/mL kanamycin. Intracellular bacteria of A549 cells after infection with Burkholderia pseudomallei were observed as early as 4 h post-infection. MNGCs were observed in the 8 after infection

and Burkholderia pseudomallei induced release of IL-8 from A549 cells in a dose- and time-dependent fashion

whereas TNF-α was not detected.       Conclusion       A burkholderia pseudomallei invaded A549 cell model is successfully established.