The many faces of Pseudomonas aeruginosa in chronic obstructive pulmonary disease

Delayed host mortality and immune response upon infection with P. aeruginosa persister cells

Chronic infections are a heavy burden on healthcare systems worldwide. Persister cells are thought to be largely responsible for chronic infection due to their tolerance to antimicrobials and recalcitrance to innate immunity factors. Pseudomonas aeruginosa is a common and clinically relevant pathogen that contains stereotypical persister cells. Despite their importance in chronic infection, there have been limited efforts to study persister cell infections in vivo. Drosophila melanogaster has a well-described innate immune response similar to that of vertebrates and is a good candidate for the development of an in vivo model of infection for persister cells. Similar to what is observed in other bacterial strains, in this work we found that infection with P. aeruginosa persister cells resulted in a delayed mortality phenotype in Caenorhabditis elegans, Arabidopsis thaliana, and D. melanogaster compared to infection with regular cells. An in-depth characterization of infected D. melanogaster found that bacterial loads differed between persister and regular cells' infections during the early stages. Furthermore, hemocyte activation and antimicrobial peptide expression were delayed/reduced in persister infections over the same time course, indicating an initial suppression of, or inability to elicit, the fly immune response. Overall, our findings support the use of D. melanogaster as a model in which to study persister cells in vivo, where this bacterial subpopulation exhibits delayed virulence and an attenuated immune response.

The COPD-Associated Polymorphism Impairs the CFTR Function to Suppress Excessive IL-8 Production upon Environmental Pathogen Exposure

COPD is a lifestyle-related disease resulting from irreversible damage to respiratory tissues mostly due to chronic exposure to environmental pollutants, including cigarette smoke. Environmental pathogens and pollutants induce the acquired dysfunction of the CFTR Cl^- channel, which is invoked in COPD. Despite the increased incidence of CFTR polymorphism R75Q or M470V in COPD patients, the mechanism of how the CFTR variant affects COPD pathogenesis remains unclear. Here, we investigated the impact of CFTR polymorphisms (R75Q, M470V) on the CFTR function in airway epithelial cell models. While wild-type (WT) CFTR suppressed the proinflammatory cytokine production induced by COPD-related pathogens including pyocyanin (PYO), R75Q- or M470V-CFTR failed. Mechanistically, the R75Q- or M470V-CFTR fractional PM activity (FPMA) was significantly lower than WT-CFTR in the presence of PYO. Notably, the CF drug Trikafta corrected the PM expression of R75Q- or M470V-CFTR even upon PYO exposure and consequently suppressed the excessive IL-8 production. These results suggest that R75Q or M470V polymorphism impairs the CFTR function to suppress the excessive proinflammatory response to environmental pathogens associated with COPD. Moreover, Trikafta may be useful to prevent the COPD pathogenesis associated with acquired CFTR dysfunction.

Hijacking of the Enterobactin Pathway by a Synthetic Catechol Vector Designed for Oxazolidinone Antibiotic Delivery in Pseudomonas aeruginosa

Enterobactin (ENT) is a tris-catechol siderophore used to acquire iron by multiple bacterial species. These ENT-dependent iron uptake systems have often been considered as potential gates in the bacterial envelope through which one can shuttle antibiotics (Trojan horse strategy). In practice, siderophore analogues containing catechol moieties have shown promise as vectors to which antibiotics may be attached. Bis- and tris-catechol vectors (BCVs and TCVs, respectively) were shown using structural biology and molecular modeling to mimic ENT binding to the outer membrane transporter PfeA in Pseudomonas aeruginosa. TCV but not BCV appears to cross the outer membrane via PfeA when linked to an antibiotic (linezolid). TCV is therefore a promising vector for Trojan horse strategies against P. aeruginosa, confirming the ENT-dependent iron uptake system as a gate to transport antibiotics into P. aeruginosa cells.

Express Yourself: Quantitative Real-Time PCR Assays for Rapid Chromosomal Antimicrobial Resistance Detection in Pseudomonas aeruginosa

The rise of antimicrobial-resistant (AMR) bacteria is a global health emergency. One critical facet of tackling this epidemic is more rapid AMR diagnosis in serious multidrug-resistant pathogens like Pseudomonas aeruginosa. Here, we designed and then validated two multiplex quantitative real-time PCR (qPCR) assays to simultaneously detect differential expression of the resistance-nodulation-division efflux pumps MexAB-OprM, MexCD-OprJ, MexEF-OprN, and MexXY-OprM, the AmpC β-lactamase, and the porin OprD, which are commonly associated with chromosomally encoded AMR. Next, qPCRs were tested on 15 sputa from 11 participants with P. aeruginosa respiratory infections to determine AMR profiles in vivo. We confirmed multiplex qPCR testing feasibility directly on sputa, representing a key advancement in in vivo AMR diagnosis. Notably, comparison of sputa with their derived isolates grown in Luria-Bertani broth (±2.5% NaCl) or a 5-antibiotic cocktail showed marked expression differences, illustrating the difficulty in replicating in vivo expression profiles in vitro. Cystic fibrosis sputa showed significantly reduced mexE and mexY expression compared with chronic obstructive pulmonary disease sputa, despite harboring fluoroquinolone- and aminoglycoside-resistant strains, indicating that these loci do not contribute to AMR in vivo. oprD was also significantly downregulated in cystic fibrosis sputa, even in the absence of contemporaneous carbapenem use, suggesting a common adaptive trait in chronic infections that may affect carbapenem efficacy. Sputum ampC expression was highest in participants receiving carbapenems (6.7 to 15×), some of whom were simultaneously receiving cephalosporins, the latter of which would be rendered ineffective by the upregulated ampC. Our qPCR assays provide valuable insights into the P. aeruginosa resistome, and their use on clinical specimens will permit timely treatment alterations that will improve patient outcomes and antimicrobial stewardship measures.

Long-Term Risk of Mortality Associated with Isolation of Pseudomonas aeruginosa in COPD: A Systematic Review and Meta-Analysis

Background

Chronic bronchial infection is frequent in chronic obstructive pulmonary disease (COPD), but the impact of the isolation of pathogenic bacteria, and in particular Pseudomonas aeruginosa (PA) in respiratory samples on the prognosis of COPD is unclear.

Methods

We conducted a systematic review of prognostic studies including patients with isolation of PA in sputum in stable state or during exacerbations of COPD. The main outcomes were all-cause mortality, respiratory mortality, and number and severity of future exacerbations. Data were expressed as hazard ratio (HR) (95% confidence interval [CI]) whenever possible.

Results

Of 2773 studies, eight were finally included (23,228 individuals). The mean age ranged from 65.5 to 73 years. Six studies reported data for all-cause mortality. The adjusted risk of death was almost double in patients with PA isolation (HR 1.95, 95% CI, 1.34 to 2.84; quality of evidence moderate). Patients with PA isolation showed a three times higher adjusted risk of readmission at 30 days after discharge (OR 3.60, 95% CI, 3.60 to 12.03, 1 study; quality of evidence very low), and more than double adjusted risk of death and hospitalization at two years (HR 2.80, 95% CI, 2.20 to 3.56, 1 study; quality of evidence very low).

Conclusion

There is moderate certainty that the isolation of PA in sputum is associated with an adjusted increased risk of death in patients with COPD.

Risk Factors and Relation with Mortality of a New Acquisition and Persistence of Pseudomonas aeruginosa in COPD Patients

The isolation of Pseudomonas aeruginosa (PA) in patients with chronic obstructive pulmonary disease (COPD) is associated with increased mortality. Yet, factors associated with first PA sputum isolation, and PA persistence have not been investigated before. The objective of the present study was to investigate risk factors for new acquisition and persistence of PA infection and their relationship with all-cause mortality in patients with COPD. Post-hoc analysis of prospectively collected cohort of 170 COPD patients (GOLD II-IV) who were free of previous PA isolation and followed up every 3-6 months for 85 [50.25-110.25] months. PA was isolated for the first time in 41 patients (24.1%) after 36 [12-60] months of follow-up. Risk factor for first PA isolation were high cumulative smoking exposure, severe airflow limitation, previous severe exacerbations, high fibrinogen levels and previous isolation of Haemophilus Influenzae. PA was isolated again one or more times during follow-up in 58.5% of these patients. This was significantly associated with the presence of CT bronchiectasis and persistence of severe exacerbations, whereas the use of inhaled antibiotic treatment after the first PA isolation (at the discretion of the attending physician) reduced PA persistence. During follow-up, 79 patients (46.4%) died. A single PA isolation did not increase mortality, but PA persistence did (HR 3.06 [1.8-5.2], p = 0.001). We conclude that PA occurs frequently in clinically stable COPD patients, risk factors for a first PA isolation and PA persistence are different, and the latter (but not the former) is associated with increased all-cause mortality.

Impact of Pseudomonas aeruginosa Infection on Patients with Chronic Inflammatory Airway Diseases

Pseudomonas aeruginosa (P. aeruginosa) is a ubiquitous and opportunistic microorganism and is considered one of the most significant pathogens that produce chronic colonization and infection of the lower respiratory tract, especially in people with chronic inflammatory airway diseases such as asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), and bronchiectasis. From a microbiological viewpoint, the presence and persistence of P. aeruginosa over time are characterized by adaptation within the host that precludes any rapid, devastating injury to the host. Moreover, this microorganism usually develops antibiotic resistance, which is accelerated in chronic infections especially in those situations where the frequent use of antimicrobials facilitates the selection of “hypermutator P. aeruginosa strain”. This phenomenon has been observed in people with bronchiectasis, CF, and the “exacerbator” COPD phenotype. From a clinical point of view, a chronic bronchial infection of P. aeruginosa has been related to more severity and poor prognosis in people with CF, bronchiectasis, and probably in COPD, but little is known on the effect of this microorganism infection in people with asthma. The relationship between the impact and treatment of P. aeruginosa infection in people with airway diseases emerges as an important future challenge and it is the most important objective of this review.

Effectiveness of Efflux Pump Inhibitors as Biofilm Disruptors and Resistance Breakers in Gram-Negative (ESKAPEE) Bacteria

Antibiotic resistance represents a significant threat to the modern healthcare provision. The ESKAPEE pathogens (Enterococcus faecium., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and Escherichia coli), in particular, have proven to be especially challenging to treat, due to their intrinsic and acquired ability to rapidly develop resistance mechanisms in response to environmental threats. The development of biofilm has been characterised as an essential contributing factor towards antimicrobial-resistance and tolerance. Several studies have implicated the involvement of efflux pumps in antibiotic resistance, both directly, via drug extrusion and indirectly, through the formation of biofilm. As a result, the underlying mechanism of these pumps has attracted considerable interest due to the potential of targeting these protein structures and developing novel adjunct therapies. Subsequent investigations have revealed the ability of efflux pump-inhibitors (EPIs) to block drug-extrusion and disrupt biofilm formation, thereby, potentiating antibiotics and reversing resistance of pathogen towards them. This review will discuss the potential of EPIs as a possible solution to antimicrobial resistance, examining different challenges to the design of these compounds, with an emphasis on Gram-negative ESKAPEE pathogens.

Targeting virulence factors as an antimicrobial approach: Pigment inhibitors

The fascinating and dangerous colored pathogens contain unique chemically pigmented molecules, which give varied and efficient assistance as virulence factors to the crucial reproduction and growth of microbes. Therefore, multiple novel strategies and inhibitors have been developed in recent years that target virulence factor pigments. However, despite the importance and significance of this topic, it has not yet been comprehensively reviewed. Moreover, research groups around the world have made successful progress against antibacterial infections by targeting pigment production, including our serial works on the discovery of CrtN inhibitors against staphyloxanthin production in Staphylococcus aureus. On the basis of the previous achievements and recent progress of our group in this field, this article will be the first comprehensive review of pigment inhibitors against colored pathogens, especially S. aureus infections, and this article includes design strategies, representative case studies, advantages, limitations, and perspectives to guide future research.

Transcriptionally Active Lung Microbiome and Its Association with Bacterial Biomass and Host Inflammatory Status

Recent studies of the microbiome proposed that resident microbes play a beneficial role in maintaining human health. Although lower respiratory tract disease is a leading cause of sickness and mortality, how the lung microbiome interacts with human health remains largely unknown. Here we assessed the association between the lung microbiome and host gene expression, cytokine concentration, and over 20 clinical features. Intriguingly, we found a stratified structure of the active lung microbiome which was significantly associated with bacterial biomass, lymphocyte proportion, human Th17 immune response, and COPD exacerbation frequency. These observations suggest that the microbiome plays a significant role in lung homeostasis. Not only microbial composition but also active functional elements and host immunity characteristics differed among different individuals. Such diversity may partially account for the variation in susceptibility to particular diseases.

Alteration of the lung microbiome has been observed in several respiratory tract diseases. However, most previous studies were based on 16S ribosomal RNA and shotgun metagenome sequencing; the viability and functional activity of the microbiome, as well as its interaction with host immune systems, have not been well studied. To characterize the active lung microbiome and its associations with host immune response and clinical features, we applied metatranscriptome sequencing to bronchoalveolar lavage fluid (BALF) samples from 25 patients with chronic obstructive pulmonary disease (COPD) and from nine control cases without known pulmonary disease. Community structure analyses revealed three distinct microbial compositions, which were significantly correlated with bacterial biomass, human Th17 immune response, and COPD exacerbation frequency. Specifically, samples with transcriptionally active Streptococcus, Rothia, or Pseudomonas had bacterial loads 16 times higher than samples enriched for Escherichia and Ralstonia. These high-bacterial-load samples also tended to undergo a stronger Th17 immune response. Furthermore, an increased proportion of lymphocytes was found in samples with active Pseudomonas. In addition, COPD patients with active Streptococcus or Rothia infections tended to have lower rates of exacerbations than patients with active Pseudomonas and patients with lower bacterial biomass. Our results support the idea of a stratified structure of the active lung microbiome and a significant host-microbe interaction. We speculate that diverse lung microbiomes exist in the population and that their presence and activities could either influence or reflect different aspects of lung health.

IMPORTANCE Recent studies of the microbiome proposed that resident microbes play a beneficial role in maintaining human health. Although lower respiratory tract disease is a leading cause of sickness and mortality, how the lung microbiome interacts with human health remains largely unknown. Here we assessed the association between the lung microbiome and host gene expression, cytokine concentration, and over 20 clinical features. Intriguingly, we found a stratified structure of the active lung microbiome which was significantly associated with bacterial biomass, lymphocyte proportion, human Th17 immune response, and COPD exacerbation frequency. These observations suggest that the microbiome plays a significant role in lung homeostasis. Not only microbial composition but also active functional elements and host immunity characteristics differed among different individuals. Such diversity may partially account for the variation in susceptibility to particular diseases.

Pseudomonas aeruginosa infection increases the readmission rate of COPD patients

Introduction

Acute exacerbation of COPD (AECOPD) leads to rapid deterioration of pulmonary function and quality of life. It is unclear whether the prognosis for AECOPD differs depending on the bacterium or virus identified. The purpose of this study is to determine whether readmission of patients with severe AECOPD varies according to the bacterium or virus identified.

Methods

We performed a retrospective review of medical records of 704 severe AECOPD events at Korea University Guro Hospital from January 2011 to May 2017. We divided events into two groups, one in which patients were readmitted within 30 days after discharge and the other in which there was no readmission.

Results

Of the 704 events, 65 were followed by readmission within 30 days. Before propensity score matching, the readmission group showed a higher rate of bacterial identification with no viral identification and a higher rate of identification with the Pseudomonas aeruginosa (P=0.003 and P=0.007, respectively). Using propensity score matching, the readmission group still showed a higher P. aeruginosa identification rate (P=0.030), but there was no significant difference in the rate of bacterial identification, with no viral identification (P=0.210). In multivariate analysis, the readmission group showed a higher P. aeruginosa identification rate than the no-readmission group (odds ratio, 4.749; 95% confidence interval, 1.296-17.041; P=0.019).

Conclusion

P. aeruginosa identification is associated with a higher readmission rate in AECOPD patients.

Inhibiting the BfrB:Bfd interaction in Pseudomonas aeruginosa causes irreversible iron accumulation in bacterioferritin and iron deficiency in the bacterial cytosol

Iron is an essential nutrient for bacteria but the reactivity of Fe²⁺ and the insolubility of Fe³⁺ present significant challenges to bacterial cells. Iron storage proteins contribute to ameliorating these challenges by oxidizing Fe²⁺ using O₂ and H₂O₂ as electron acceptors, and by compartmentalizing Fe³⁺. Two types of iron-storage proteins coexist in bacteria, the ferritins (Ftn) and the heme-containing bacterioferritins (Bfr), but the reasons for their coexistence are largely unknown. P. aeruginosa cells harbor two iron storage proteins (FtnA and BfrB), but nothing is known about their relative contributions to iron homeostasis. Prior studies in vitro have shown that iron mobilization from BfrB requires specific interactions with a ferredoxin (Bfd), but the relevance of the BfrB:Bfd interaction to iron homeostasis in P. aeruginosa is unknown. In this work we explore the repercussions of (i) deleting the bfrB gene, and (ii) perturbing the BfrB:Bfd interaction in P. aeruginosa cells by either deleting the bfd gene or by replacing the wild type bfrB gene with a L68A/E81A double mutant allele in the P. aeruginosa chromosome. The effects of the mutations were evaluated by following the accumulation of iron in BfrB, analyzing levels of free and total intracellular iron, and by characterizing the ensuing iron homeostasis dysregulation phenotypes. The results reveal that P. aeruginosa accumulates iron mainly in BfrB, and that the nutrient does not accumulate in FtnA to detectable levels, even after deletion of the bfrB gene. Perturbing the BfrB:Bfd interaction causes irreversible flow of iron into BfrB, which leads to the accumulation of unusable intracellular iron while severely depleting the levels of free intracellular iron, which drives the cells to an acute iron starvation response despite harboring "normal" levels of total intracellular iron. These results are discussed in the context of a dynamic equilibrium between free cytosolic Fe²⁺ and Fe³⁺ compartmentalized in BfrB, which functions as a buffer to oppose rapid changes of free cytosolic iron. Finally, we also show that P. aeruginosa cells utilize iron stored in BfrB for growth in iron-limiting conditions, and that the utilization of BfrB-iron requires a functional BfrB:Bfd interaction.

The Human Virome Protein Cluster Database (HVPC): A Human Viral Metagenomic Database for Diversity and Function Annotation

Human virome, including those of bacteria (bacteriophages) have received an increasing attention recently, owing to the rapid developments in human microbiome research and the awareness of the far-reaching influence of microbiomes on health and disease. Nevertheless, human viromes are still underrepresented in literature making viruses a virtually untapped resource of diversity, functional and physiological information. Here we present the human virome protein cluster database as an effort to improve functional annotation and characterization of human viromes. The database was built out of hundreds of virome datasets from six different body sites. We also show the utility of this database through its use for the characterization of three bronchoalveolar lavage (BAL) viromes from one healthy control in addition to one moderate and one severe chronic obstructive pulmonary disease (COPD) patients. The use of the database allowed for a better functional annotation, which were otherwise poorly characterized when limited to annotation using sequences from full-length viral genomes. In addition, our BAL samples gave a first insight into viral communities of COPD patients and confirm a state of dysbiosis for viruses that increases with disease progression. Moreover, they shed light on the potential role of phages in the horizontal gene transfer of bacterial virulence factors, a phenomenon that highlights a possible contribution of phages to etiopathology.

An Antipersister Strategy for Treatment of Chronic Pseudomonas aeruginosa Infections

Bacterial persisters are a quasidormant subpopulation of cells that are tolerant to antibiotic treatment. The combination of the aminoglycoside tobramycin with fumarate as an antibacterial potentiator utilizes an antipersister strategy that is aimed at reducing recurrent Pseudomonas aeruginosa infections by enhancing the killing of P. aeruginosa persisters. Stationary-phase cultures of P. aeruginosa were used to generate persister cells. A range of tobramycin concentrations was tested with a range of metabolite concentrations to determine the potentiation effect of the metabolite under a variety of conditions, including a range of pH values and in the presence of azithromycin or cystic fibrosis (CF) patient sputum. In addition, 96-well dish biofilm and colony biofilm assays were performed, and the cytotoxicity of the tobramycin-fumarate combination was determined utilizing a lactate dehydrogenase (LDH) assay. Enhanced killing of up to 6 orders of magnitude of P. aeruginosa persisters over a range of CF isolates, including mucoid and nonmucoid strains, was observed for the tobramycin-fumarate combination compared to killing with tobramycin alone. Furthermore, significant fumarate-mediated potentiation was seen in the presence of azithromycin or CF patient sputum. Fumarate also reduced the cytotoxicity of tobramycin-treated P. aeruginosa to human epithelial airway cells. Finally, in mucoid and nonmucoid CF isolates, complete eradication of P. aeruginosa biofilm was observed in the colony biofilm assay due to fumarate potentiation. These data suggest that a combination of tobramycin with fumarate as an antibacterial potentiator may be an attractive therapeutic for eliminating recurrent P. aeruginosa infections in CF patients through the eradication of bacterial persisters.

An epoxide hydrolase secreted by Pseudomonas aeruginosa decreases mucociliary transport and hinders bacterial clearance from the lung

The opportunistic pathogen Pseudomonas aeruginosa colonizes the lungs of susceptible individuals by deploying virulence factors targeting host defenses. The secreted factor Cif (cystic fibrosis transmembrane conductance regulator inhibitory factor) dysregulates the endocytic recycling of CFTR and thus reduces CFTR abundance in host epithelial membranes. We have postulated that the decrease in ion secretion mediated by Cif would slow mucociliary transport and decrease bacterial clearance from the lungs. To test this hypothesis, we explored the effects of Cif in cultured epithelia and in the lungs of mice. We developed a strategy to interpret the "hurricane-like" motions observed in reconstituted cultures and identified a Cif-mediated decrease in the velocity of mucus transport in vitro. Presence of Cif also increased the number of bacteria recovered at two time points in an acute mouse model of pneumonia caused by P. aeruginosa. Furthermore, recent work has demonstrated an inverse correlation between the airway concentrations of Cif and 15-epi-lipoxin A_4, a proresolving lipid mediator important in host defense and the resolution of pathogen-initiated inflammation. Here, we observe elevated levels of 15-epi-lipoxin A₄ in the lungs of mice infected with a strain of P. aeruginosa that expresses only an inactive form of cif compared with those mice infected with wild-type P. aeruginosa. Together these data support the inclusion of Cif on the list of virulence factors that assist P. aeruginosa in colonizing and damaging the airways of compromised patients. Furthermore, this study establishes techniques that enable our groups to explore the underlying mechanisms of Cif effects during respiratory infection.

Similar virulence properties of infection and colonization associated Pseudomonas aeruginosa

PURPOSE

Pseudomonas aeruginosa is one of the agents that are commonly implicated in nosocomial infections. However, it is also present as a commensal in various body sites of healthy persons, making the diagnosis of infection by culture difficult. A number of virulence factors expressed by the organism have been implicated in its pathogenicity. We undertook this study to identify the host and organism factors associated with infection.

METHODOLOGY

Pathogenic, colonizing and environmental isolates were tested for apr, lasB, the T3SS effector exoenzymes (exoS, exoT, exoU and exoY) and toxA genes, biofilm production and antimicrobial susceptibility. The isolates were further typed by RAPD.

RESULTS

Eighty-seven isolates from 61 patients, including 11 environmental isolates, were obtained. None of the virulence factors were found to be significantly associated with infection, and nor was the antimicrobial susceptibility. The presence of the exoU gene and infection by MDR strains correlated significantly with the duration of hospital stay. Positivity for exoS and exoU genes was found to be strongly correlated with multi-drug resistance. exoU positivity correlated strongly with fluoroquinolone resistance. Sinks in the ward and intensive care unit were found to be a niche for XDR P. aeruginosa. Eighty-five isolates were typeable using the ERIC2 primer, showing 71 distinct RAPD patterns with >15 % difference in UPGMA-generated dice coefficients.

CONCLUSIONS

exoU positivity is associated with severe disease, as evidenced by the longer duration of hospital stay of these patients. However, the presence of virulence factors or multi-drug resistance in the cultured strain should not prompt the administration of anti-pseudomonal chemotherapy.

Bronchial microbiome, PA biofilm-forming capacity and exacerbation in severe COPD patients colonized by P. aeruginosa

AIM

The bronchial microbiome of severe chronic obstructive pulmonary disease patients colonized by Pseudomonas aeruginosa was analyzed using 16S rRNA gene sequencing to identify differences related to biofilm-forming capacity.

PATIENTS & METHODS

Patient sputum samples from 21 patients were studied.

RESULTS

Statistically significant differences related to biofilm-forming capacity were only found for genera with relative abundances <1%, and Fusobacterium was over-represented when biofilm-forming capacity was high. Genera with relative abundances >50% which increased from baseline were observed in 10/14 exacerbations, but corresponded to Pseudomonas only in three episodes, while other pathogenic genera were identified in seven.

CONCLUSION

The bronchial microbiome shows differences according with P. aeruginosa biofilm-forming capacity. Pathogenic microorganisms other than P. aeruginosa cause a significant part of the exacerbations in colonized chronic obstructive pulmonary disease patients.

Prophylaxis for Pneumocystis jiroveci pneumonia: is it a necessity in pulmonary patients on high-dose, chronic corticosteroid therapy without AIDS?

The benefit of prophylaxis for Pneumocystis jirovecii pneumonia (PJP) is well documented in immunocompromised patients, particularly those with HIV and/or AIDS; therefore, guidelines dictate this as standard of care. However, there is a paucity of literature regarding those without HIV and/or AIDS who are potentially predisposed to PJP, including patients with sarcoidosis, cryptogenic organizing pneumonia, interstitial lung disease, asthma and chronic obstructive pulmonary disease, who may require high dose of prolonged corticosteroids for disease maintenance or to prevent relapses. In this review, the authors examine the available literature regarding prophylaxis in these groups, elaborate on the pathogenesis of PJP, when to suspect PJP in these patients, as well as explore current recommendations that guide clinical practice regarding implementation of PJP prophylaxis, namely with trimethoprim/sulfamethoxazole being the preferred agent. In summary, the role of PJP prophylaxis in non-HIV patients on chronic steroids remains controversial. The authors present a review of the literature to provide better guidance to the clinician regarding the need to initiate PJP prophylaxis in this patient population.

Fucosylated surfactant protein-D is a biomarker candidate for the development of chronic obstructive pulmonary disease

We previously reported that knockout mice for α1,6-fucosyltransferase (Fut8), which catalyzes the biosynthesis of core-fucose in N-glycans, develop emphysema and that Fut8 heterozygous knockout mice are more sensitive to cigarette smoke-induced emphysema than wild-type mice. Moreover, a lower FUT8 activity was found to be associated with a faster decline in lung function among chronic obstructive pulmonary disease (COPD) patients. These results led us to hypothesize that core-fucosylation levels in a glycoprotein could be used as a biomarker for COPD. We focused on a lung-specific glycoprotein, surfactant protein D (SP-D), which plays a role in immune responses and is present in the distal airways, alveoli, and blood circulation. The results of a glycomic analysis reported herein demonstrate the presence of a core-fucose in an N-glycan on enriched SP-D from pooled human sera. We developed an antibody-lectin enzyme immunoassay (EIA) for assessing fucosylation (core-fucose and α1,3/4 fucose) in COPD patients. The results indicate that fucosylation levels in serum SP-D are significantly higher in COPD patients than in non-COPD smokers. The severity of emphysema was positively associated with fucosylation levels in serum SP-D in smokers. Our findings suggest that increased fucosylation levels in serum SP-D are associated with the development of COPD.

BIOLOGICAL SIGNIFICANCE

It has been proposed that serum SP-D concentrations are predictive of COPD pathogenesis, but distinguishing between COPD patients and healthy individuals to establish a clear cut-off value is difficult because smoking status highly affects circulating SP-D levels. Herein, we focused on N-glycosylation in SP-D and examined whether or not N-glycosylation patterns in SP-D are associated with the pathogenesis of COPD. We performed an N-glycomic analysis of human serum SP-D and the results show that a core-fucose is present in its N-glycan. We also found that the N-glycosylation in serum SP-D was indeed altered in COPD, that is, fucosylation levels including core-fucosylation are significantly increased in COPD patients compared with non-COPD smokers. The severity of emphysema was positively associated with fucosylation levels in serum SP-D in smokers. Our findings shed new light on the discovery and/or development of a useful biomarker based on glycosylation changes for diagnosing COPD. This article is part of a Special Issue entitled: HUPO 2014.

Bronchial microbiome of severe COPD patients colonised by Pseudomonas aeruginosa

The bronchial microbiome in severe COPD during stability and exacerbation in patients chronically colonised by Pseudomonas aeruginosa (PA), has not been defined. Our objective was to determine the characteristics of the bronchial microbiome of severe COPD patients colonised and not colonised by P. aeruginosa and its changes during exacerbation. COPD patients with severe disease and frequent exacerbations were categorised according to chronic colonisation by P. aeruginosa. Sputum samples were obtained in stability and exacerbation, cultured, and analysed by 16S rRNA gene amplification and pyrosequencing. Sixteen patients were included, 5 of them showing chronic colonisation by P. aeruginosa. Pseudomonas genus had significantly higher relative abundance in stable colonised patients (p = 0.019), but no significant differences in biodiversity parameters were found between the two groups (Shannon, 3 (2-4) vs 3 (2-3), p = 0.699; Chao1, 124 (77-159) vs 140 (115-163), p = 0.364). In PA-colonised patients bronchial microbiome changed to a microbiome similar to non-PA-colonised patients during exacerbations. An increase in the relative abundance over 20 % during exacerbation was found for Streptococcus, Pseudomonas, Moraxella, Haemophilus, Neisseria, Achromobacter and Corynebacterium genera, which include recognised potentially pathogenic microorganisms, in 13 patients colonised and not colonised by P. aeruginosa with paired samples. These increases were not identified by culture in 5 out of 13 participants (38.5 %). Stable COPD patients with severe disease and PA-colonised showed a similar biodiversity to non-PA-colonised patients, with a higher relative abundance of Pseudomonas genus in bronchial secretions. Exacerbation in severe COPD patients showed the same microbial pattern, independently of previous colonisation by P. aeruginosa.

Flagellin/Toll-like receptor 5 response was specifically attenuated by keratan sulfate disaccharide via decreased EGFR phosphorylation in normal human bronchial epithelial cells

Bacterial or viral infection of the airway plays a critical role in the pathogenesis and exacerbation of chronic obstructive pulmonary disease (COPD) which is expected to be the 3rd leading cause of death by 2020. The induction of inflammatory responses in immune cells as well as airway epithelial cells is observed in the disease process. There is thus a pressing need for the development of new therapeutics. Keratan sulfate (KS) is the major glycosaminoglycans (GAGs) of airway secretions, and is synthesized by epithelial cells on the airway surface. Here we report that a KS disaccharide, [SO3(-)-6]Galβ1-4[SO3(-)-6]GlcNAc, designated as L4, suppressed the production of Interleukin-8 (IL-8) stimulated by flagellin, a Toll-like receptor (TLR) 5 agonist, in normal human bronchial epithelial (NHBE) cells. Such suppressions were not observed by other L4 analogues, N-acetyllactosamine or chondroitin-6-sulfate disaccharide. Moreover, treatment of NHBE cells with L4 inhibited the flagellin-stimulated phosphorylation of epidermal growth factor receptor (EGFR), the down stream signaling pathway of TLRs in NHBE cells. These results suggest that L4 specifically blocks the interaction of flagellin with TLR5 and subsequently suppresses IL-8 production in NHBE cells. Taken together, L4 represents a potential molecule for prevention and treatment of airway inflammatory responses to bacteria infections, which play a critical role in exacerbation of COPD.

Pyocyanin effects on respiratory epithelium: relevance in Pseudomonas aeruginosa airway infections

Pseudomonas aeruginosa (PA) uses several virulence factors to establish chronic respiratory infections in bronchiectasis, chronic obstructive pulmonary disease, and cystic fibrosis (CF) patients. One of its toxins, pyocyanin (PYO), is a redox-active pigment that is required for full virulence in animal models and has been detected in patients' airway secretions. PYO promotes virulence by interfering with several cellular functions in host cells including electron transport, cellular respiration, energy metabolism, gene expression, and innate immune mechanisms. This review summarizes recent advances in PYO biology with special attention to current views on its role in human airway infections and on its interactions with the first line of our airway defense, the respiratory epithelium.