Invasion of Burkholderia cepacia complex isolates into lung epithelial cells involves glycolipid receptors.

Burkholderia cepacia complex (Bcc) is a group of opportunistic cystic fibrosis (CF) pathogens that invade lung epithelial cells. The mechanisms of invasion are poorly understood, in particular, the receptors utilised by this bacterium in the invasion process have not been identified. The aim of this study was to investigate the epithelial receptors involved in the invasion of Bcc isolates. We confirmed that invasion into two lung epithelial cell lines (16HBE14o- and CFBE41o-) which have a non-CF and CF phenotype, respectively, is receptor mediated and showed that pre-treatment of these epithelial cell lines with α- or ß-galactosidase reduced invasion of isolates of two species of Bcc, Burkholderia multivorans and Burkholderia cenocepacia. In contrast, removal of mucin had no significant effect. Biotinylated Bcc strains were shown to bind to purified glycolipids separated by thin layer chromatography, albeit different patterns of binding were associated with different strains. Invasion of CF lung epithelial cells (CFBE41o-) by all three Bcc strains examined was significantly reduced by treatment of cells with inhibitors of glycolipid biosynthesis. Although the specific glycolipid involved in each case has not been elucidated, it is apparent that invasion of lung epithelial cells is mediated via binding to glycosphingolipid receptors.

Invasion and biofilm formation of Burkholderia dolosa is comparable with Burkholderia cenocepacia and Burkholderia multivorans.

BACKGROUND: Colonisation with Burkholderia cepacia complex pathogens has been associated with accelerated decline in cystic fibrosis (CF) patients. The two most common species among the CF community are Burkholderia cenocepacia and Burkholderia multivorans. However, Burkholderia dolosa has recently been causing concern due to its transmissibility and virulence in CF patients. METHODS: We have compared the ability of five B. dolosa strains to invade lung epithelial cells in vitro with other members of the Bcc. The bacterial epithelial cell interaction was visualised by transmission electron microscopy. We have also examined the ability of these strains to form biofilms in vitro. RESULTS: We have found that members of this species can invade pulmonary epithelial cells in vitro as readily as those from B. cenocepacia and B. multivorans. Confirmation of intracellular invasion was obtained by transmission electron microscopy. B. dolosa strains were readily observed in membrane bound vesicles inside the lung epithelial cells. In addition, strains from this species were capable of forming strong biofilms at a level comparable to the more clinically relevant species. CONCLUSIONS: B. dolosa shows comparable virulence characteristics in vitro to the two most clinically relevant species indicating precautions should be taken when this species is identified in the CF population.