Localization of Burkholderia cepacia Complex Bacteria in Cystic Fibrosis Lungs and Interactions with Pseudomonas aeruginosa in Hypoxic Mucus

Schwab, Ute; Abdullah, Lubna H.; Perlmutt, Olivia; Albert, Daniel B.; Davis, C. William; Arnold, Roland R.; Yankaskas, James R.; Gilligan, Peter H.; Neubauer, Heiner; Randell, Scott H.; Boucher, Richard C.

doi:10.1128/iai.01876-14

Cited by 109 publications

(126 citation statements)

References 74 publications

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“…Previous studies have demonstrated that a well-studied CF pathogen, P. aeruginosa, colonizes the respiratory tract of CF patients and triggers an immune response (34)(35)(36)(37)(38)(39). It was previously thought to primarily be an extracellular pathogen, which is supported in a histological study of CF lungs (33), though other work in eye models suggests that P. aeruginosa may be able to invade and survive inside host cells (40)(41)(42)(43)(44). Both B. cenocepacia, the best-studied of the BCC members, and P. aeruginosa have been shown to induce production of cytokines (i.e., tumor necrosis factor [TNF], interleukin-6 [IL-6], IL-8, and IL-1␤) in murine alveolar macrophages in vitro (45)(46)(47).…”

supporting

confidence: 60%

“…More recent work in transplanted or autopsied CF lungs suggests that BCC strains, including B. dolosa and B. cenocepacia, can be found primarily associated within host cells, particularly macrophages, or in mucus (33). Previous studies have demonstrated that a well-studied CF pathogen, P. aeruginosa, colonizes the respiratory tract of CF patients and triggers an immune response (34)(35)(36)(37)(38)(39).…”

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confidence: 99%

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Immune Recognition of the Epidemic Cystic Fibrosis Pathogen Burkholderia dolosa

et al. 2017

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Burkholderia dolosa caused an outbreak in the cystic fibrosis (CF) clinic at Boston Children's Hospital from 1998 to 2005 and led to the infection of over 40 patients, many of whom died due to complications from infection by this organism. To assess whether B. dolosa significantly contributes to disease or is recognized by the host immune response, mice were infected with a sequenced outbreak B. dolosa strain, AU0158, and responses were compared to those to the well-studied CF pathogen Pseudomonas aeruginosa. In parallel, mice were also infected with a polar flagellin mutant of B. dolosa to examine the role of flagella in B. dolosa lung colonization. The results showed a higher persistence in the host by B. dolosa strains, and yet, neutrophil recruitment and cytokine production were lower than those with P. aeruginosa. The ability of host immune cells to recognize B. dolosa was then assessed, B. dolosa induced a robust cytokine response in cultured cells, and this effect was dependent on the flagella only when bacteria were dead. Together, these results suggest that B. dolosa can be recognized by host cells in vitro but may avoid or suppress the host immune response in vivo through unknown mechanisms. B. dolosa was then compared to other Burkholderia species and found to induce similar levels of cytokine production despite being internalized by macrophages more than Burkholderia cenocepacia strains. These data suggest that B. dolosa AU0158 may act differently with host cells and is recognized differently by immune systems than are other Burkholderia strains or species.

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confidence: 60%

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confidence: 99%

Immune Recognition of the Epidemic Cystic Fibrosis Pathogen Burkholderia dolosa

et al. 2017

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“…These mechanisms include efflux pumps, chromosomally encoded ␤-lactamases, and decreased outer membrane permeability (5). In addition, B. cepacia complex species are known to grow in the CF lung as a biofilm or in clusters of bacteria (6), which can act as a significant barrier to the effective delivery of drug intracellularly.…”

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confidence: 99%

Activity of Tobramycin against Cystic Fibrosis Isolates of Burkholderia cepacia Complex Grown as Biofilms

Kennedy

Beaudoin

Yau

et al. 2016

Antimicrob Agents Chemother

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f Pulmonary infection with Burkholderia cepacia complex in cystic fibrosis (CF) patients is associated with more-rapid lung function decline and earlier death than in CF patients without this infection. In this study, we used confocal microscopy to visualize the effects of various concentrations of tobramycin, achievable with systemic and aerosolized drug administration, on mature B. cepacia complex biofilms, both in the presence and absence of CF sputum. After 24 h of growth, biofilm thickness was significantly reduced by exposure to 2,000 g/ml of tobramycin for Burkholderia cepacia, Burkholderia multivorans, and Burkholderia vietnamiensis; 200 g/ml of tobramycin was sufficient to reduce the thickness of Burkholderia dolosa biofilm. With a more mature 48-h biofilm, significant reductions in thickness were seen with tobramycin at concentrations of >100 g/ml for all Burkholderia species. In addition, an increased ratio of dead to live cells was observed in comparison to control with tobramycin concentrations of >200 g/ml for B. cepacia and B. dolosa (24 h) and >100 g/ml for Burkholderia cenocepacia and B. dolosa (48 h). Although sputum significantly increased biofilm thickness, tobramycin concentrations of 1,000 g/ml were still able to significantly reduce biofilm thickness of all B. cepacia complex species with the exception of B. vietnamiensis. In the presence of sputum, 1,000 g/ml of tobramycin significantly increased the dead-to-live ratio only for B. multivorans compared to control. In summary, although killing is attenuated, high-dose tobramycin can effectively decrease the thickness of B. cepacia complex biofilms, even in the presence of sputum, suggesting a possible role as a suppressive therapy in CF.

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“…In fact, all mucosal sites throughout the human body harbor both commensal and pathogenic organisms that possess mucin-degrading enzymes capable of deriving nutrients from host (22)(23)(24). Indeed, several studies have described the degradation and utilization of mucins by CF-associated microbiota (25)(26)(27)(28)(29). For example, multiple studies have shown that P. aeruginosa and other pathogens (e.g., Burkholderia cepacia complex [BCC]) harbor mucin sulfatase activity capable of utilizing sialylated mucin oligosaccharides as a source of sulfur (26,28).…”

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confidence: 99%

Genome-Wide Survey of Pseudomonas aeruginosa PA14 Reveals a Role for the Glyoxylate Pathway and Extracellular Proteases in the Utilization of Mucin

2017

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Chronic airway infections by the opportunistic pathogen Pseudomonas aeruginosa are a major cause of mortality in cystic fibrosis (CF) patients. Although this bacterium has been extensively studied for its virulence determinants, biofilm growth, and immune evasion mechanisms, comparatively little is known about the nutrient sources that sustain its growth in vivo. Respiratory mucins represent a potentially abundant bioavailable nutrient source, although we have recently shown that canonical pathogens inefficiently use these host glycoproteins as a growth substrate. However, given that P. aeruginosa, particularly in its biofilm mode of growth, is thought to grow slowly in vivo, the inefficient use of mucin glycoproteins may be relevant to its persistence within the CF airways. To this end, we used whole-genome fitness analysis, combining transposon mutagenesis with high-throughput sequencing, to identify genetic determinants required for P. aeruginosa growth using intact purified mucins as a sole carbon source. Our analysis reveals a biphasic growth phenotype, during which the glyoxylate pathway and amino acid biosynthetic machinery are required for mucin utilization. Secondary analyses confirmed the simultaneous liberation and consumption of acetate during mucin degradation and revealed a central role for the extracellular proteases LasB and AprA. Together, these studies describe a molecular basis for mucin-based nutrient acquisition by P. aeruginosa and reveal a host-pathogen dynamic that may contribute to its persistence within the CF airways.KEYWORDS cystic fibrosis, glyoxylate pathway, mucin, Pseudomonas aeruginosa, TnSeq C ystic fibrosis (CF), a common and lethal autosomal recessive disease, results from mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein (1). Impaired CFTR function leads to abnormal transepithelial ion transport and a thickened, dehydrated mucus layer that overlays the epithelium of several organs, including the lungs (2, 3). Within the airways, defective mucociliary clearance facilitates chronic colonization by a complex bacterial community, and the ensuing inflammatory response leads to bronchiectasis, progressive lung damage, and eventual respiratory failure in a majority of CF patients (2). Despite the recent surge in studies describing a polymicrobial etiology of CF, Pseudomonas aeruginosa continues to be widely recognized as the primary driver of disease progression (4). This opportunistic pathogen can reach densities of 10 7 to 10 9 CFU/g of sputum, particularly in late stages of disease, suggesting that the mucus environment of the lower airways provides the bacterium an ideal growth environment (5, 6). A deeper understanding of this milieu, and its ability to sustain P. aeruginosa growth in vivo is critically important for improved disease management.The mucosal layer covering the respiratory epithelium is a complex mixture of water,

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Localization of Burkholderia cepacia Complex Bacteria in Cystic Fibrosis Lungs and Interactions with Pseudomonas aeruginosa in Hypoxic Mucus

Cited by 109 publications

References 74 publications

Immune Recognition of the Epidemic Cystic Fibrosis Pathogen Burkholderia dolosa

Immune Recognition of the Epidemic Cystic Fibrosis Pathogen Burkholderia dolosa

Activity of Tobramycin against Cystic Fibrosis Isolates of Burkholderia cepacia Complex Grown as Biofilms

Genome-Wide Survey of Pseudomonas aeruginosa PA14 Reveals a Role for the Glyoxylate Pathway and Extracellular Proteases in the Utilization of Mucin

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