Intracellular survival of Burkholderia cepacia complex isolates in the presence of macrophage cell activation.
Strains of the Burkholderia cepacia complex have emerged as a serious threat to patients with cystic fibrosis due to their ability to infect the lung and cause, in some patients, a necrotizing pneumonia that is often lethal. It has recently been shown that several strains of the B. cepacia complex can escape intracellular killing by free-living amoebae following phagocytosis. In this work, the ability of two B. cepacia complex strains to resist killing by macrophages was explored. Using fluorescence microscopy, electron microscopy and a modified version of the gentamicin-protection assay, we demonstrate that B. cepacia CEP021 (genomovar VI), and Burkholderia vietnamiensis (previously B. cepacia genomovar V) CEP040 can survive in PU5-1.8 murine macrophages for a period of at least 5 d without significant bacterial replication. Furthermore, bacterial entry into macrophages stimulated production of tumour necrosis factor and primed them to release toxic oxygen radicals following treatment with phorbol myristoyl acetate. These effects were probably caused by bacterial LPS, as they were blocked by polymyxin B. Infected macrophages primed with interferon gamma produced less nitric oxide than interferon-gamma-primed uninfected cells. We propose that the ability of B. cepacia to resist intracellular killing by phagocytic cells may play a role in the pathogenesis of cystic fibrosis lung infection. Our data are consistent with a model where repeated cycles of phagocytosis and cellular activation without bacterial killing may promote a deleterious inflammatory response causing tissue destruction and decay of lung function.
Saini
Lalit S
LS
Department of Microbiology and Immunology1 and Department of Medicine2, University of Western Ontario, London, Ontario, N6A 5C1, Canada.
Galsworthy
Sara B
SB
Department of Microbiology and Immunology1 and Department of Medicine2, University of Western Ontario, London, Ontario, N6A 5C1, Canada.
John
Michael A
MA
Department of Microbiology and Infection Control, London Health Sciences Centre, London, Ontario, N6A 4G5, Canada3.|Department of Microbiology and Immunology1 and Department of Medicine2, University of Western Ontario, London, Ontario, N6A 5C1, Canada.
Valvano
Miguel A
MA
Department of Microbiology and Immunology1 and Department of Medicine2, University of Western Ontario, London, Ontario, N6A 5C1, Canada.
D000818:Animals; D019117:Burkholderia / Q000502:physiology; D019121:Burkholderia Infections / Q000382:microbiology*; D016956:Burkholderia cepacia / Q000502:physiology*; D002460:Cell Line; D003550:Cystic Fibrosis / Q000382:microbiology*; D005434:Flow Cytometry; D006801:Humans; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology / Q000382:microbiology*; D051379:Mice; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D009569:Nitric Oxide / Q000096:biosynthesis; D010587:Phagocytosis; D016897:Respiratory Burst; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide