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1.  IFN-γ Stimulates Autophagy-Mediated Clearance of Burkholderia cenocepacia in Human Cystic Fibrosis Macrophages 
PLoS ONE  2014;9(5):e96681.
Burkholderia cenocepacia is a virulent pathogen that causes significant morbidity and mortality in patients with cystic fibrosis (CF), survives intracellularly in macrophages, and uniquely causes systemic infections in CF. Autophagy is a physiologic process that involves engulfing non-functional organelles and proteins and delivering them for lysosomal degradation, but also plays a role in eliminating intracellular pathogens, including B. cenocepacia. Autophagy is defective in CF but can be stimulated in murine CF models leading to increased clearance of B. cenocepacia, but little is known about autophagy stimulation in human CF macrophages. IFN-γ activates macrophages and increases antigen presentation while also inducing autophagy in macrophages. We therefore, hypothesized that treatment with IFN-γ would increase autophagy and macrophage activation in patients with CF. Peripheral blood monocyte derived macrophages (MDMs) were obtained from CF and non-CF donors and subsequently infected with B. cenocepacia. Basal serum levels of IFN-γ were similar between CF and non-CF patients, however after B. cenocepacia infection there is deficient IFN-γ production in CF MDMs. IFN-γ treated CF MDMs demonstrate increased co-localization with the autophagy molecule p62, increased autophagosome formation, and increased trafficking to lysosomes compared to untreated CF MDMs. Electron microscopy confirmed IFN-γ promotes double membrane vacuole formation around bacteria in CF MDMs, while only single membrane vacuoles form in untreated CF cells. Bacterial burden is significantly reduced in autophagy stimulated CF MDMs, comparable to non-CF levels. IL-1β production is decreased in CF MDMs after IFN-γ treatment. Together, these results demonstrate that IFN-γ promotes autophagy-mediated clearance of B. cenocepacia in human CF macrophages.
PMCID: PMC4010498  PMID: 24798083
2.  Invasion and Intracellular Survival of Burkholderia cepacia 
Infection and Immunity  2000;68(1):24-29.
Burkholderia cepacia has emerged as an important pulmonary pathogen in immunocompromised patients and in patients with cystic fibrosis (CF). Little is known about the virulence factors and pathogenesis of B. cepacia, although the persistent and sometimes invasive infections caused by B. cepacia suggest that the organism possesses mechanisms for both cellular invasion and evasion of the host immune response. In this study, cultured human cells were used to analyze the invasion and intracellular survival of B. cepacia J2315, a highly transmissible clinical isolate responsible for morbidity and mortality in CF patients. Quantitative invasion and intracellular growth assays demonstrated that B. cepacia J2315 was able to enter, survive, and replicate intracellularly in U937-derived macrophages and A549 pulmonary epithelial cells. Transmission electron microscopy of infected macrophages confirmed the presence of intracellular B. cepacia and showed that intracellular bacteria were contained within membrane-bound vacuoles. An environmental isolate of B. cepacia, strain J2540, was also examined for its ability to invade and survive intracellularly in cultured human cells. J2540 entered cultured macrophages with an invasion frequency similar to that of the clinical strain, but it was less invasive than the clinical strain in epithelial cells. In marked contrast to the clinical strain, the environmental isolate was unable to survive or replicate intracellularly in either cultured macrophages or epithelial cells. Invasion and intracellular survival may play important roles in the ability of virulent strains of B. cepacia to evade the host immune response and cause persistent infections in CF patients.
PMCID: PMC97097  PMID: 10603364
3.  Akt-mediated pro-inflammatory response of mononuclear phagocytes infected with Burkholderia cenocepacia occurs by a novel GSK3β-dependent, IKK-independent mechanism 
The environmental bacterium Burkholderia cenocepacia causes opportunistic lung infections in immunocompromised individuals, particularly in patients with cystic fibrosis. Infections in these patients are associated with exacerbated inflammation leading to rapid decay of lung function and in some cases resulting in cepacia syndrome, which is characterized by a fatal acute necrotizing pneumonia and sepsis. B. cenocepacia can survive intracellularly in macrophages by altering the maturation of the phagosome, but very little is known on macrophage responses to the intracellular infection. Here, we have examined the role of the PI3K/Akt signaling pathway in B. cenocepacia-infected monocytes and macrophages. We show that PI3K/Akt activity was required for NF-κB activity and the secretion of pro-inflammatory cytokines during infection with B. cenocepacia. In contrast to previous observations in epithelial cells infected with other Gram-negative bacteria, Akt did not enhance IKK or NF-κB p65 phosphorylation but rather inhibited GSK3β, a negative regulator of NF-κB transcriptional activity. This novel mechanism of modulation of NF-κB activity may provide a unique therapeutic target for controlling excessive inflammation upon B. cenocepacia infection.
PMCID: PMC3131456  PMID: 21697459
4.  Host Evasion by Burkholderia cenocepacia 
Burkholderia cenocepacia is an opportunistic respiratory pathogen of individuals with cystic fibrosis (CF). Some strains of B. cenocepacia are highly transmissible and resistant to almost all antibiotics. Approximately one-third of B. cenocepacia infected CF patients go on to develop fatal “cepacia syndrome.” During the last two decades, substantial progress has been made with regards to evasion of host innate defense mechanisms by B. cenocepacia. Almost all strains of B. cenocepacia have the capacity to survive and replicate intracellularly in both airway epithelial cells and macrophages, which are primary sentinels of the lung and play a pivotal role in clearance of infecting bacteria. Those strains of B. cenocepacia, which express both cable pili and the associated 22 kDa adhesin are also capable of transmigrating across airway epithelium and persist in mouse models of infection. In this review, we will discuss how this type of interaction between B. cenocepacia and host may lead to persistence of bacteria as well as lung inflammation in CF patients.
PMCID: PMC3417383  PMID: 22919590
cystic fibrosis; innate immunity; inflammation; bacterial pathogenesis; lung infection; cable pili; airway epithelium; macrophages
5.  Burkholderia cenocepacia BC2L-C Is a Super Lectin with Dual Specificity and Proinflammatory Activity 
PLoS Pathogens  2011;7(9):e1002238.
Lectins and adhesins are involved in bacterial adhesion to host tissues and mucus during early steps of infection. We report the characterization of BC2L-C, a soluble lectin from the opportunistic pathogen Burkholderia cenocepacia, which has two distinct domains with unique specificities and biological activities. The N-terminal domain is a novel TNF-α-like fucose-binding lectin, while the C-terminal part is similar to a superfamily of calcium-dependent bacterial lectins. The C-terminal domain displays specificity for mannose and l-glycero-d-manno-heptose. BC2L-C is therefore a superlectin that binds independently to mannose/heptose glycoconjugates and fucosylated human histo-blood group epitopes. The apo form of the C-terminal domain crystallized as a dimer, and calcium and mannose could be docked in the binding site. The whole lectin is hexameric and the overall structure, determined by electron microscopy and small angle X-ray scattering, reveals a flexible arrangement of three mannose/heptose-specific dimers flanked by two fucose-specific TNF-α-like trimers. We propose that BC2L-C binds to the bacterial surface in a mannose/heptose-dependent manner via the C-terminal domain. The TNF-α-like domain triggers IL-8 production in cultured airway epithelial cells in a carbohydrate-independent manner, and is therefore proposed to play a role in the dysregulated proinflammatory response observed in B. cenocepacia lung infections. The unique architecture of this newly recognized superlectin correlates with multiple functions including bacterial cell cross-linking, adhesion to human epithelia, and stimulation of inflammation.
Author Summary
The glycoconjugates that cover the surface of eukaryotic cells are a target for pathogens that use protein receptors for binding to the carbohydrate moieties exposed. Opportunistic bacteria such as Pseudomonas aeruginosa and Burkholderia species of the B. cepacia complex display a wide range of adhesins and soluble lectins that are specific for human oligosaccharides. We characterized the complex architecture of one Burkholderia cenocepacia soluble lectin, and analysed the specificity of two different lectin subdomains. We propose that one of the subdomains attaches to sugars present on the bacteria surface, enabling bacterial aggregation in microcolonies. The other subdomain attaches to sugars in human airways. In addition, this domain can elicit an inflammatory response in airways cells. Burkholderia cenocepacia causes lethal infections in cystic fibrosis patients and soluble lectins may be novel therapeutics targets.
PMCID: PMC3164656  PMID: 21909279
6.  Targeting the Intracellular Environment in Cystic Fibrosis: Restoring Autophagy as a Novel Strategy to Circumvent the CFTR Defect 
Cystic fibrosis (CF) patients harboring the most common deletion mutation of the CF transmembrane conductance regulator (CFTR), F508del, are poor responders to potentiators of CFTR channel activity which can be used to treat a small subset of CF patients who genetically carry plasma membrane (PM)-resident CFTR mutants. The misfolded F508del-CFTR protein is unstable in the PM even if rescued by pharmacological agents that prevent its intracellular retention and degradation. CF is a conformational disease in which defective CFTR induces an impressive derangement of general proteostasis resulting from disabled autophagy. In this review, we discuss how rescuing Beclin 1 (BECN1), a major player of autophagosome formation, either by means of direct gene transfer or indirectly by administration of proteostasis regulators, could stabilize F508del-CFTR at the PM. We focus on the relationship between the improvement of peripheral proteostasis and CFTR PM stability in F508del-CFTR homozygous bronchial epithelia or mouse lungs. Moreover, this article reviews recent pre-clinical evidence indicating that targeting the intracellular environment surrounding the misfolded mutant CFTR instead of protein itself could constitute an attractive therapeutic option to sensitize patients carrying the F508del-CFTR mutation to the beneficial action of CFTR potentiators on lung inflammation.
PMCID: PMC3549520  PMID: 23346057
cystic fibrosis; CFTR; proteostasis regulators; autophagy; BECN1
7.  Targeting autophagy as a novel strategy for facilitating the therapeutic action of potentiators on ΔF508 cystic fibrosis transmembrane conductance regulator 
Autophagy  2012;8(11):1657-1672.
Channel activators (potentiators) of cystic fibrosis (CF) transmembrane conductance regulator (CFTR), can be used for the treatment of the small subset of CF patients that carry plasma membrane-resident CFTR mutants. However, approximately 90% of CF patients carry the misfolded ΔF508-CFTR and are poorly responsive to potentiators, because ΔF508-CFTR is intrinsically unstable at the plasma membrane (PM) even if rescued by pharmacological correctors. We have demonstrated that human and mouse CF airways are autophagy deficient due to functional sequestration of BECN1 and that the tissue transglutaminase-2 inhibitor, cystamine, or antioxidants restore BECN1-dependent autophagy and reduce SQSTM1/p62 levels, thus favoring ΔF508-CFTR trafficking to the epithelial surface. Here, we investigated whether these treatments could facilitate the beneficial action of potentiators on ΔF508-CFTR homozygous airways. Cystamine or the superoxide dismutase (SOD)/catalase-mimetic EUK-134 stabilized ΔF508-CFTR at the plasma membrane of airway epithelial cells and sustained the expression of CFTR at the epithelial surface well beyond drug withdrawal, overexpressing BECN1 and depleting SQSTM1. This facilitates the beneficial action of potentiators in controlling inflammation in ex vivo ΔF508-CFTR homozygous human nasal biopsies and in vivo in mouse ΔF508-CFTR lungs. Direct depletion of Sqstm1 by shRNAs in vivo in ΔF508-CFTR mice synergized with potentiators in sustaining surface CFTR expression and suppressing inflammation. Cystamine pre-treatment restored ΔF508-CFTR response to the CFTR potentiators genistein, Vrx-532 or Vrx-770 in freshly isolated brushed nasal epithelial cells from ΔF508-CFTR homozygous patients. These findings delineate a novel therapeutic strategy for the treatment of CF patients with the ΔF508-CFTR mutation in which patients are first treated with cystamine and subsequently pulsed with CFTR potentiators.
PMCID: PMC3494594  PMID: 22874563
cystic fibrosis; autophagy; therapy; cystamine; CFTR potentiators
8.  Epidemiology and Clinical Course of Burkholderia cepacia Complex Infections, Particularly Those Caused by Different Burkholderia cenocepacia Strains, among Patients Attending an Italian Cystic Fibrosis Center 
Journal of Clinical Microbiology  2004;42(4):1491-1497.
In this study, the epidemiology of Burkholderia cepacia complex (Bcc) recovered from the sputum of 75 patients attending the Genoa Cystic Fibrosis (CF) Center at the Gaslini Children's Hospital (Genoa, Italy) was investigated, and the clinical course of the CF patients infected with the different species and genomovars of Bcc was evaluated. All isolates were analyzed for genomovar status by recA gene polymorphism and subsequently random amplified polymorphic DNA fingerprinting. Burkholderia cenocepacia is the predominant species recovered from the CF patients infected with Bcc at the Genoa CF Center. Of the other eight species comprising the Bcc, only a few isolates belonging to B. cepacia genomovar I, Burkholderia stabilis, and Burkholderia pyrrocinia were found. Of the four recA lineages of B. cenocepacia, most patients were infected by epidemic strains belonging to lineages IIIA and IIID, whereas only a few patients harbored IIIB strains. Patient-to-patient spread of Bcc among CF patients was mostly associated with B. cenocepacia, in particular with strains belonging to recA lineages IIIA and IIID. The mortality of CF patients infected with Bcc at the Genoa CF Center was significantly higher than mortality among CF patients not infected with Bcc. All of the deaths were associated with the presence of B. cenocepacia, except the case of a patient infected with B. cepacia genomovar I. Within B. cenocepacia, infection with epidemic strains belonging to lineages IIIA and IIID was associated with higher rates of mortality than was infection with lineage IIIB strains. No significant differences in lung function, body weight, and mortality rate were observed between patients infected with epidemic strains belonging to either B. cenocepacia IIIA or B. cenocepacia IIID.
PMCID: PMC387599  PMID: 15070994
9.  Enhanced Susceptibility to Pulmonary Infection with Burkholderia cepacia in Cftr−/− Mice 
Infection and Immunity  2001;69(8):5138-5150.
Progressive pulmonary infection is the dominant clinical feature of cystic fibrosis (CF), but the molecular basis for this susceptibility remains incompletely understood. To study this problem, we developed a model of chronic pneumonia by repeated instillation of a clinical isolate of Burkholderia cepacia (genomovar III, ET12 strain), an opportunistic gram-negative bacterium, from a case of CF into the lungs of Cftr m1unc−/− (Cftr−/−) and congenic Cftr+/+ controls. Nine days after the last instillation, the CF transmembrane regulator knockout mice showed persistence of viable bacteria with chronic severe bronchopneumonia while wild-type mice remained healthy. The histopathological changes in the lungs of the susceptible Cftr−/− mice were characterized by infiltration of a mixed inflammatory-cell population into the peribronchiolar and perivascular spaces, Clara cell hyperplasia, mucus hypersecretion in airways, and exudation into alveolar airspaces by a mixed population of macrophages and neutrophils. An increased proportion of neutrophils was observed in bronchoalveolar lavage fluid from the Cftr−/− mice, which, despite an increased bacterial load, demonstrated minimal evidence of activation. Alveolar macrophages from Cftr−/− mice also demonstrated suboptimal activation. These observations suggest that the pulmonary host defenses are compromised in lungs from animals with CF, as manifested by increased susceptibility to bacterial infection and lung injury. This murine model of chronic pneumonia thus reflects, in part, the situation in human patients and may help elucidate the mechanisms leading to defective host defense in CF.
PMCID: PMC98610  PMID: 11447196
10.  Potential mechanisms underlying the acute lung dysfunction and bacterial extrapulmonary dissemination during Burkholderia cenocepacia respiratory infection 
Respiratory Research  2010;11(1):4.
Burkholderia cenocepacia, an opportunistic pathogen that causes lung infections in cystic fibrosis (CF) patients, is associated with rapid and usually fatal lung deterioration due to necrotizing pneumonia and sepsis, a condition known as cepacia syndrome. The key bacterial determinants associated with this poor clinical outcome in CF patients are not clear. In this study, the cytotoxicity and procoagulant activity of B. cenocepacia from the ET-12 lineage, that has been linked to the cepacia syndrome, and four clinical isolates recovered from CF patients with mild clinical courses were analysed in both in vitro and in vivo assays.
B. cenocepacia-infected BEAS-2B epithelial respiratory cells were used to investigate the bacterial cytotoxicity assessed by the flow cytometric detection of cell staining with propidium iodide. Bacteria-induced procoagulant activity in cell cultures was assessed by a colorimetric assay and by the flow cytometric detection of tissue factor (TF)-bearing microparticles in cell culture supernatants. Bronchoalveolar lavage fluids (BALF) from intratracheally infected mice were assessed for bacterial proinflammatory and procoagulant activities as well as for bacterial cytotoxicity, by the detection of released lactate dehydrogenase.
ET-12 was significantly more cytotoxic to cell cultures but clinical isolates Cl-2, Cl-3 and Cl-4 exhibited also a cytotoxic profile. ET-12 and CI-2 were similarly able to generate a TF-dependent procoagulant environment in cell culture supernatant and to enhance the release of TF-bearing microparticles from infected cells. In the in vivo assay, all bacterial isolates disseminated from the mice lungs, but Cl-2 and Cl-4 exhibited the highest rates of recovery from mice livers. Interestingly, Cl-2 and Cl-4, together with ET-12, exhibited the highest cytotoxicity. All bacteria were similarly capable of generating a procoagulant and inflammatory environment in animal lungs.
B. cenocepacia were shown to exhibit cytotoxic and procoagulant activities potentially implicated in bacterial dissemination into the circulation and acute pulmonary decline detected in susceptible CF patients. Improved understanding of the mechanisms accounting for B. cenocepacia-induced clinical decline has the potential to indicate novel therapeutic strategies to be included in the care B. cenocepacia-infected patients.
PMCID: PMC2817657  PMID: 20082687
11.  Burkholderia cenocepacia ET12 Strain Activates TNFR1 Signaling in Cystic Fibrosis Airway Epithelial Cells 
Cellular microbiology  2007;10(1):188-201.
Burkholderia cenocepacia is an important pulmonary pathogen in individuals with cystic fibrosis. Infection is often associated with severe pulmonary inflammation and some patients develop a fatal necrotizing pneumonia and sepsis (‘cepacia syndrome’). The mechanisms by which this species causes severe pulmonary inflammation are poorly understood. Here, we demonstrate that B. cenocepacia BC7, a potentially virulent representative of the epidemic ET12 lineage binds to tumor necrosis factor receptor I (TNFR1) and activates TNFR1-related signaling pathway similar to TNF-α, a natural ligand for TNFR1. This interaction participates in stimulating a robust IL-8 production from CF airway epithelial cells. In contrast, BC45, a relatively less virulent ET12 representative, and ATCC 25416, an environmental B. cepacia strain do not bind to TNFR1 and stimulate only minimal IL-8 production from CF cells. Further, TNFR1 expression is increased in CF airway epithelial cells compared to non-CF cells. We also show that B. cenocepacia ET12 strain colocaizes with TNFR1 in vitro and in the lungs of CF patient who died due to infection with B. cenocepacia, ET12 strain. Together, these results suggest that interaction of B. cenocepacia, ET12 strain with TNFR1 may contribute to robust inflammatory responses elicited by this organism.
PMCID: PMC3226749  PMID: 17697131
cepacia complex; inflammation; tumor necrosis factor; interleukin
12.  Outcome for patients colonised with Burkholderia cepacia in a Birmingham adult cystic fibrosis clinic and the end of an epidemic. 
Thorax  1996;51(4):374-377.
BACKGROUND: There has been increasing concern since 1979 about the emergence of Pseudomonas cepacia (Burkholderia cepacia) in patients with cystic fibrosis in the UK and elsewhere. Colonisation of the sputum has been shown to be associated with increased morbidity and mortality. Evidence suggests person to person transmission and some centres have segregated those colonised with B cepacia from other patients with cystic fibrosis. The outcome of patients colonised by B cepacia has been studied, together with the effects of strict segregation. METHODS: The outcome in 18 patients with sputum colonised by B cepacia was compared with that in age, sex, and severity matched controls with no evidence of B cepacia colonisation by a retrospective case note study. RESULTS: No difference between cases or controls were found in the 24 month period prior to colonisation by B cepacia in lung function, number of days in hospital, or outpatient visits. Colonisation led to an increased rate of loss of lung function and utilisation of hospital services. There was an increase in the numbers of transplants and deaths amongst the cases. Since 1992 there have been only three new cases of B cepacia colonisation and the incidence and prevalence of the organism has fallen dramatically since segregation commenced. CONCLUSIONS: B cepacia appears to be linked to the decline in colonised individuals. There was no evidence that colonisation occurred in patients declining for other reasons. B cepacia colonisation confers a worse prognosis than Pseudomonas aeruginosa alone. Segregation appears to limit the spread of the organism from infected individuals to other patients with cystic fibrosis.
PMCID: PMC1090671  PMID: 8733488
13.  Identification of Burkholderia cenocepacia Genes Required for Bacterial Survival In Vivo  
Infection and Immunity  2004;72(7):4010-4022.
Burkholderia cenocepacia (formerly Burkholderia cepacia complex genomovar III) causes chronic lung infections in patients with cystic fibrosis. In this work, we used a modified signature-tagged mutagenesis (STM) strategy for the isolation of B. cenocepacia mutants that cannot survive in vivo. Thirty-seven specialized plasposons, each carrying a unique oligonucleotide tag signature, were constructed and used to examine the survival of 2,627 B. cenocepacia transposon mutants, arranged in pools of 37 unique mutants, after a 10-day lung infection in rats by using the agar bead model. The recovered mutants were screened by real-time PCR, resulting in the identification of 260 mutants which presumably did not survive within the lungs. These mutants were repooled into smaller pools, and the infections were repeated. After a second screen, we isolated 102 mutants unable to survive in the rat model. The location of the transposon in each of these mutants was mapped within the B. cenocepacia chromosomes. We identified mutations in genes involved in cellular metabolism, global regulation, DNA replication and repair, and those encoding bacterial surface structures, including transmembrane proteins and cell surface polysaccharides. Also, we found 18 genes of unknown function, which are conserved in other bacteria. A subset of 12 representative mutants that were individually examined using the rat model in competition with the wild-type strain displayed reduced survival, confirming the predictive value of our STM screen. This study provides a blueprint to investigate at the molecular level the basis for survival and persistence of B. cenocepacia within the airways.
PMCID: PMC427415  PMID: 15213146
14.  The Burkholderia cepacia Epidemic Strain Marker Is Part of a Novel Genomic Island Encoding Both Virulence and Metabolism-Associated Genes in Burkholderia cenocepacia  
Infection and Immunity  2004;72(3):1537-1547.
The Burkholderia cepacia epidemic strain marker (BCESM) is a useful epidemiological marker for virulent B. cenocepacia strains that infect patients with cystic fibrosis. However, there was no evidence that the original marker, identified by random amplified polymorphic DNA fingerprinting, contributed to pathogenicity. Here we demonstrate that the BCESM is part of a novel genomic island encoding genes linked to both virulence and metabolism. The BCESM was present on a 31.7-kb low-GC-content island that encoded 35 predicted coding sequences (CDSs): an N-acyl homoserine lactone (AHL) synthase gene (cciI) and corresponding transcriptional regulator (cciR), representing the first time cell signaling genes have been found on a genomic island; fatty acid biosynthesis genes; an IS66 family transposase; transcriptional regulator CDSs; amino acid metabolism genes; and a group of hypothetical genes. Mutagenesis of the AHL synthase, amidase (amiI), and porin (opcI) genes on the island was carried out. Testing of the isogenic mutants in a rat model of chronic lung infection demonstrated that the amidase played a role in persistence, while the AHL synthase and porin were both involved in virulence. The island, designated the B. cenocepacia island (cci), is the first genomic island to be defined in the B. cepacia complex and its discovery validates the original epidemiological correlation of the BCESM with virulent CF strains. The features of the cci, which overlap both pathogenicity and metabolism, expand the concept of bacterial pathogenicity islands and illustrate the diversity of accessory functions that can be acquired by lateral gene transfer in bacteria.
PMCID: PMC356040  PMID: 14977960
15.  Role of Flagella in Host Cell Invasion by Burkholderia cepacia  
Infection and Immunity  2002;70(4):1799-1806.
Burkholderia cepacia is an important opportunistic human pathogen that affects immunocompromised individuals, particularly cystic fibrosis (CF) patients. Colonization of the lungs of a CF patient by B. cepacia can lead not only to a decline in respiratory function but also to an acute systemic infection, such as bacteremia. We have previously demonstrated that a CF clinical isolate of B. cepacia, strain J2315, can invade and survive within cultured respiratory epithelial cells. In order to further characterize the mechanisms of invasion of B. cepacia, we screened a transposon-generated mutant library of strain J2315 for mutants defective in invasion of A549 respiratory epithelial cells. Here we describe isolation and characterization of a nonmotile mutant of B. cepacia with reduced invasiveness due to disruption of fliG, which encodes a component of the motor-switch complex of the flagellar basal body. We also found that a defined null mutation in fliI, a gene encoding a highly conserved ATPase required for protein translocation via the flagellar type III secretion system, also resulted in loss of motility and a significant reduction in invasion. Both mutants lacked detectable intracellular flagellin and failed to export detectable amounts of flagellin into culture supernatants, suggesting that disruption of fliG and fliI impaired flagellar biogenesis. The reduction in invasion did not appear to be due to defective adherence of the flagellar mutants to A549 cells, suggesting that functional flagella and motility are required for full invasiveness of B. cepacia. Our findings indicate that flagellum-mediated motility may facilitate penetration of host epithelial barriers by B. cepacia, contributing to establishment of infection and systemic spread of the organism.
PMCID: PMC127839  PMID: 11895941
16.  Lipoxin A4 and Platelet Activating Factor Are Involved in E. coli or LPS-Induced Lung Inflammation in CFTR-Deficient Mice 
PLoS ONE  2014;9(3):e93003.
CFTR (cystic fibrosis transmembrane conductance regulator) is expressed by both neutrophils and platelets. Lack of functional CFTR could lead to severe lung infection and inflammation. Here, we found that mutation of CFTR (F508del) or inhibition of CFTR in mice led to more severe thrombocytopenia, alveolar neutrocytosis and bacteriosis, and lower lipoxin A4/MIP-2 (macrophage inhibitory protein-2) or lipoxin A4/neutrophil ratios in the BAL (bronchoalveolar lavage) during acute E. coli pneumonia. In vitro, inhibition of CFTR promotes MIP-2 production in LPS-stimulated neutrophils; however, lipoxin A4 could dose-dependently suppress this effect. In LPS-induced acute lung inflammation, blockade of PSGL-1 (P-selectin glycoprotein ligand-1) or P-selectin, antagonism of PAF by WEB2086, or correction of mutated CFTR trafficking by KM11060 could significantly increase plasma lipoxin A4 levels in F508del relevant to wildtype mice. Concurrently, F508del mice had higher plasma platelet activating factor (PAF) levels and PAF-AH activity compared to wildtype under LPS challenge. Inhibiting hydrolysis of PAF by a specific PAF-AH (PAF-acetylhydrolase) inhibitor, MAFP, could worsen LPS-induced lung inflammation in F508del mice compared to vehicle treated F508del group. Particularly, depletion of platelets in F508del mice could significantly decrease plasma lipoxin A4 and PAF-AH activity and deteriorate LPS-induced lung inflammation compared to control F508del mice. Taken together, lipoxin A4 and PAF are involved in E. coli or LPS-induced lung inflammation in CFTR-deficient mice, suggesting that lipoxin A4 and PAF might be therapeutic targets for ameliorating CFTR-deficiency deteriorated lung inflammation.
PMCID: PMC3966846  PMID: 24671173
17.  Molecular Analysis of Burkholderia cepacia Complex Isolates from a Portuguese Cystic Fibrosis Center: a 7-Year Study 
Journal of Clinical Microbiology  2003;41(9):4113-4120.
This work reports results of a systematic molecular analysis involving 113 Burkholderia cepacia complex isolates obtained from 23 cystic fibrosis (CF) patients under surveillance over a 7-year period at the major Portuguese CF center, the Santa Maria Hospital in Lisbon. The majority of the isolates were serial isolates from persistently infected patients (more than one-half of the population examined). In agreement with previous studies, B. cenocepacia (formerly genomovar III) was the most prevalent species; it was isolated from 52% of the patients infected with B. cepacia complex isolates. Contrasting with previous studies, a very significant percentage of the Portuguese CF subpopulation examined was infected with B. cepacia genomovar I (36%) and B. stabilis (18%). B. multivorans was recovered from two of the infected patients. All four of the species or genomovars were associated with poor clinical outcome, including the cepacia syndrome, and gave rise to chronic and transient infections, with the clinical condition depending on the patient and other still-unidentified factors. The B. cepacia epidemic strain marker region was found exclusively in genomovar III strains, while cblA was detected in genomovars I and III, only. There was no clear relation between the presence of these markers and transmissibility. Altogether, our results indicate that the use of these markers or the genomovar status in identifying patients at higher risk for infection is uncertain.
PMCID: PMC193798  PMID: 12958234
18.  Nasal Immunization with Burkholderia multivorans Outer Membrane Proteins and the Mucosal Adjuvant Adamantylamide Dipeptide Confers Efficient Protection against Experimental Lung Infections with B. multivorans and B. cenocepacia▿  
Infection and Immunity  2007;75(6):2740-2752.
Chronic lung infection by opportunistic pathogens, such as Pseudomonas aeruginosa and members of the Burkholderia cepacia complex, is a major cause of morbidity and mortality in patients with cystic fibrosis. Outer membrane proteins (OMPs) of gram-negative bacteria are promising vaccine antigen candidates. In this study, we evaluated the immunogenicity, protection, and cross-protection conferred by intranasal vaccination of mice with OMPs from B. multivorans plus the mucosal adjuvant adamantylamide dipeptide (AdDP). Robust mucosal and systemic immune responses were stimulated by vaccination of naive animals with OMPs from B. multivorans and B. cenocepacia plus AdDP. Using a mouse model of chronic pulmonary infection, we observed enhanced clearance of B. multivorans from the lungs of vaccinated animals, which correlated with OMP-specific secretory immunoglobulin A responses. Furthermore, OMP-immunized mice showed rapid resolution of the pulmonary infection with virtually no lung pathology after bacterial challenge with B. multivorans. In addition, we demonstrated that administration of B. multivorans OMP vaccine conferred protection against B. cenocepacia challenge in this mouse infection model, suggesting that OMPs provide cross-protection against the B. cepacia complex. Therefore, we concluded that mucosal immunity to B. multivorans elicited by intranasal vaccination with OMPs plus AdDP could prevent early steps of colonization and infection with B. multivorans and also ameliorate lung tissue damage, while eliciting cross-protection against B. cenocepacia. These results support the notion that therapies leading to increased mucosal immunity in the airways may help patients with cystic fibrosis.
PMCID: PMC1932907  PMID: 17296759
19.  Long-Term Colonization of the Cystic Fibrosis Lung by Burkholderia cepacia Complex Bacteria: Epidemiology, Clonal Variation, and Genome-Wide Expression Alterations 
Long-term respiratory infections with Burkholderia cepacia complex (Bcc) bacteria in cystic fibrosis (CF) patients generally lead to a more rapid decline in lung function and, in some cases, to a fatal necrotizing pneumonia known as the “cepacia syndrome.” Bcc bacteria are ubiquitous in the environment and are recognized as serious opportunistic pathogens that are virtually impossible to eradicate from the CF lung, posing a serious clinical threat. The epidemiological survey of Bcc bacteria involved in respiratory infections at the major Portuguese CF Treatment Center at Santa Maria Hospital, in Lisbon, has been carried out by our research group for the past 16 years, covering over 500 clinical isolates where B. cepacia and B. cenocepacia are the predominant species, with B. stabilis, B. contaminans, B. dolosa, and B. multivorans also represented. The systematic and longitudinal study of this CF population during such an extended period of time represents a unique case–study, comprehending 41 Bcc-infected patients (29 pediatric and 12 adult) of whom around 70% have been persistently colonized between 7 months and 9 years. During chronic infection, the CF airways represent an evolving ecosystem, with multiple phenotypic variants emerging from the clonal population and becoming established in the patients’ airways as the result of genetic adaptation. Understanding the evolutionary mechanisms involved is crucial for an improved therapeutic outcome of chronic infections in CF. This review focuses on our contribution to the understanding of these adaptive mechanisms based on extensive phenotypic, genotypic, and genome-wide expression approaches of selected Bcc clonal variants obtained during long-term colonization of the CF airways.
PMCID: PMC3417363  PMID: 22919578
cystic fibrosis; chronic respiratory infection; long-term colonization; Burkholderia cepacia complex; Burkholderia cenocepacia; genome-wide expression; clonal variation
20.  Studies on the Involvement of the Exopolysaccharide Produced by Cystic Fibrosis-Associated Isolates of the Burkholderia cepacia Complex in Biofilm Formation and in Persistence of Respiratory Infections 
Journal of Clinical Microbiology  2004;42(7):3052-3058.
Bacteria belonging to the Burkholderia cepacia complex (BCC) are important opportunistic pathogens that lead to respiratory infections in patients with cystic fibrosis (CF). The clinical outcome following colonization with BCC bacteria is highly variable, and so far, unpredictable. A large percentage (80 to 90%) of BCC isolates from CF patients produce the exopolysaccharide (EPS) cepacian, which has been hypothesized to play a role in the colonization and persistence of these bacteria in the CF lung. In this work, we demonstrate that although it is not required for the initiation of biofilm formation, cepacian plays a role in the establishment of thick biofilms. This conclusion was based on a comparison of the abilities of EPS-defective mutants derived from a B. cepacia mucoid CF isolate by random plasposon insertion mutagenesis and the ability of the parental strain to form biofilms. However, the systematic characterization of 108 CF isolates, corresponding to 15 distinct strains, indicated that other strain-dependent factors are also involved in the development of thick, mature biofilms. The isolates examined belonged to the species B. cepacia, B. multivorans, B. cenocepacia, and B. stabilis and were obtained during a 7-year period of surveillance from 21 CF patients receiving care at the major Portuguese CF center. Most of them (90%) were serial isolates from 12 persistently infected patients. In spite of the concept that bacteria growing in biofilms display more resistance to antibiotics and to host phagocyte killing than do planktonically growing cells, no clear correlation could be established between the ability of the various strains examined to produce EPS and/or to form biofilms in vitro and the persistence or virulence of the respiratory infections they caused in different patients.
PMCID: PMC446245  PMID: 15243059
21.  Functional Quorum Sensing Systems are Maintained during Chronic Burkholderia cepacia Complex Infections in Patients with Cystic Fibrosis 
The Journal of Infectious Diseases  2011;203(3):383-392.
Quorum sensing (QS) contributes to the virulence of Pseudomonas aeruginosa and Burkholderia cepacia complex lung infections. P. aeruginosa QS mutants are frequently isolated from patients with cystic fibrosis. The objective of this study was to determine whether similar adaptations occur over time in B. cepacia complex isolates. Forty-five Burkholderia multivorans and Burkholderia cenocepacia sequential isolates from patients with cystic fibrosis were analyzed for N-acyl-homoserine lactone activity. All but one isolate produced N-acyl-homoserine lactones. The B. cenocepacia N-acyl-homoserine lactone–negative isolate contained mutations in cepR and cciR. Growth competition assays were performed that compared B. cenocepacia clinical and laboratory defined wild-type and QS mutants. Survival of the laboratory wild-type and QS mutants varied, dependent on the mutation. The clinical wild-type isolate demonstrated a growth advantage over its QS mutant. These data suggest that there is a selective advantage for strains with QS systems and that QS mutations do not occur at a high frequency in B. cepacia complex isolates.
PMCID: PMC3071112  PMID: 21208930
22.  Prevalence and clonality of Burkholderia cepacia complex genomovars in UK patients with cystic fibrosis referred for lung transplantation 
Thorax  2004;59(6):526-528.
Background: It has previously been reported that patients infected with Burkholderia cenocepacia (genomovar III) before lung transplantation have a poorer outcome than those with other B cepacia complex infections.
Methods: An extensive study was conducted to determine the prevalence and clonality of B cepacia complex genomovars isolated from patients referred for transplant assessment between 1989 to the present and, where appropriate, whether strain type was related to transplant outcome.
Results: Isolates from 29 patients were identified as B cepacia complex organisms by molecular analysis. Thirteen patients (45%) were infected with the highly transmissible ET-12 strain of B cenocepacia recA lineage III-A, while all remaining patients were infected with genetically unique B cenocepacia, B multivorans, and B vietnamiensis strains. All previously reported deaths following transplantation were associated with ET-12 infection.
Conclusions: The ET-12 strain is the predominant cause of B cenocepacia infections in patients with cystic fibrosis referred to our pulmonary transplant centre and is associated with poor transplant outcomes using standard treatment regimens.
PMCID: PMC1747049  PMID: 15170040
23.  Profiling of Burkholderia cepacia Secretome at Mid-Logarithmic and Early-Stationary Phases of Growth 
PLoS ONE  2011;6(10):e26518.
Burkholderia cepacia is a Gram-negative pathogen that causes serious respiratory infections in immunocompromised patients and individuals with cystic fibrosis. This bacterium is known to release extracellular proteins that may be involved in virulence.
Methodology/Principal Findings
In the present study, B. cepacia grown to mid-logarithmic and early-stationary phases were investigated on their ability to invade and survive intracellularly in A549 lung epithelial cells in order to discern the fate of these bacteria in the pathogenesis of B. cepacia lung infections in in vitro condition. The early-stationary phase B. cepacia was demonstrated to be more invasive than mid-logarithmic phase. In addition, culture supernatants of B. cepacia obtained from these phases of growth were also demonstrated to cause different cytotoxic potency on the A549 human lung epithelial cells. Profiling of the supernatants using the gel-based proteomics approach identified 43 proteins that were commonly released in both the growth phases and 40 proteins newly-released at the early-stationary phase. The latter proteins may account for the higher cytotoxic activity of the early-stationary culture supernatant compared to that obtained at the mid-logarithmic phase. Among the newly-released proteins in the early-stationary phase supernatant were flagellar hook-associated domain protein (FliD), flagellar hook-associated protein (FlgK), TonB-dependent siderophore (Fiu), Elongation factor G (FusA), phosphoglycerate kinase (Pgk) and sulfatase (AslA) which are known for their virulence.
Differences in the ability of B. cepacia to invade and survive intracellularly inside the epithelial cells at different phases of growth may improve our understanding of the varied disease progressions associated with B. cepacia infections. In addition, the identified culture supernatant proteins may be used as targets for the development of new strategies to control B. cepacia infection using agents that can block their release.
PMCID: PMC3202529  PMID: 22046299
24.  Identification and Onion Pathogenicity of Burkholderia cepacia Complex Isolates from the Onion Rhizosphere and Onion Field Soil▿  
Applied and Environmental Microbiology  2008;74(10):3121-3129.
Burkholderia cepacia complex strains are genetically related but phenotypically diverse organisms that are important opportunistic pathogens in patients with cystic fibrosis (CF,) as well as pathogens of onion and banana, colonizers of the rhizospheres of many plant species, and common inhabitants of bulk soil. Genotypic identification and pathogenicity characterization were performed on B. cepacia complex isolates from the rhizosphere of onion and organic soils in Michigan. A total of 3,798 putative B. cepacia complex isolates were recovered on Pseudomonas cepacia azelaic acid tryptamine and trypan blue tetracycline semiselective media during the 2004 growing season from six commercial onion fields located in two counties in Michigan. Putative B. cepacia complex isolates were identified by hybridization to a 16S rRNA gene probe, followed by duplex PCR using primers targeted to the 16S rRNA gene and recA sequences and restriction fragment length polymorphism analysis of the recA sequence. A total of 1,290 isolates, 980 rhizosphere and 310 soil isolates, were assigned to the species B. cepacia (160), B. cenocepacia (480), B. ambifaria (623), and B. pyrrocinia (27). The majority of isolates identified as B. cepacia (85%), B. cenocepacia (90%), and B. ambifaria (76%) were pathogenic in a detached onion bulb scale assay and caused symptoms of water soaking, maceration, and/or necrosis. A phylogenetic analysis of recA sequences from representative B. cepacia complex type and panel strains, along with isolates collected in this study, revealed that the B. cenocepacia isolates associated with onion grouped within the III-B lineage and that some strains were closely related to strain AU1054, which was isolated from a CF patient. This study revealed that multiple B. cepacia complex species colonize the onion rhizosphere and have the potential to cause sour skin rot disease of onion. In addition, the onion rhizosphere is a natural habitat and a potential environmental source of B. cenocepacia.
PMCID: PMC2394932  PMID: 18344334
25.  Burkholderia cenocepacia and Burkholderia multivorans: influence on survival in cystic fibrosis 
Thorax  2004;59(11):948-951.
Introduction: Burkholderia cepacia infection has been associated with a poor prognosis for patients with cystic fibrosis (CF). It is now recognised that organisms classified as B cepacia comprise a number of distinct genomic species each known as a genomovar of the B cepacia complex (BCC). The outcome of infection for CF patients with individual genomovars is unknown. The clinical outcome of infection with the two most commonly isolated genomovars (B cenocepacia and B multivorans) was studied at a specialist CF centre between 1982 and 2003.
Methods: The numbers of patients who progressed from initial to chronic infection were assessed. Control groups were created by matching patients with chronic BCC infection by percentage forced expiratory volume in 1 second with patients with Pseudomonas aeruginosa infection. Outcome measures were survival time, deaths from "cepacia syndrome", rate of decline in spirometry and body mass index (BMI), and treatment requirements.
Results: Forty nine patients had an initial infection with either B multivorans (n = 16) or B cenocepacia (n = 33); 8/16 and 31/33, respectively, developed chronic infection (p<0.001). Deaths from "cepacia syndrome" occurred in both BCC groups. Patients with B cenocepacia infection had a shorter survival than patients with P aeruginosa infection (p = 0.01). There was no difference in survival between CF patients infected with B multivorans and P aeruginosa. There were no observed differences in changes in spirometry and BMI or treatment requirements between the BCC groups and respective controls.
Conclusion: In CF, the genomovar status of BCC may influence both the likelihood of progression from initial to chronic infection and the overall survival of the patients.
PMCID: PMC1746874  PMID: 15516469

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