Outcome of Burkholderia cepacia colonisation in an adult cystic fibrosis centre

Eradication of Burkholderia cepacia complex in cystic fibrosis patients with inhalation of amiloride and tobramycin combined with oral cotrimoxazole

This case series suggests that successful eradication therapy of BCC in cystic fibrosis can be done with a combination of inhaled and oral medication, which in many cases may eliminate the need for intensive treatment with intravenous antibiotics https://bit.ly/40oOMIn.

Real-world use of ivacaftor in Canada: A retrospective analysis using the Canadian Cystic Fibrosis Registry

BACKGROUND

Ivacaftor is a CFTR potentiator with demonstrated efficacy in clinical trials and has been rapidly adopted within the CF community. Given the uptake of ivacaftor in eligible people, identifying a comparator group not on modulators to measure effectiveness is difficult. We evaluated health outcomes in individuals with G551D and non-G551D genotypes on ivacaftor using real-world longitudinal data.

METHODS

This population-based observational study compared clinical trajectories pre-post ivacaftor using the Canadian CF Registry from 2006 to 01-01 through 2018-12-31. Piece-wise linear mixed-effects models were used to compare lung function, nutritional status, pulmonary exacerbations, and Pseudomonas colonization pre- and post-ivacaftor. Multivariable models were used to adjust for confounding factors.

RESULTS

Forced expiratory volume in 1 second (FEV1) increased significantly by 5.7 percent predicted (95% confidence interval (CI) 3.9, 7.5; p<0.001) after initiation of ivacaftor. FEV1 decline rate was attenuated to -0.30% (95% CI -0.9, 0.29; p = 0.32) predicted/year post-ivacaftor, compared with -0.75% (95% CI -1.12, -0.37; p<0.001) predicted/year pre-ivacaftor, although this difference did not reach statistical significance. BMI percentiles also increased post-ivacaftor (6.57 percentiles, 95% CI 3.91, 9.24; p<0.001). Pulmonary exacerbations showed a nonsignificant reduction of 18% (RR 0.82, 95% CI 0.61, 1.11; p = 0.19) and the odds of a positive sputum culture for Pseudomonas aeruginosa decreased in the post-ivacaftor period (odds ratio 0.44, 95% CI 0.30, 0.63; p<0.001).

CONCLUSIONS

This real-world, observational study demonstrated improvement in health outcomes in a broad population of people with CF. Additional studies are needed to evaluate the impact of ivacaftor on quality of life and survival.

Intracellular survival and innate immune evasion of Burkholderia cepacia: Improved understanding of quorum sensing-controlled virulence factors, biofilm, and inhibitors

Burkholderia cepacia complex (Bcc) are opportunistic pathogens implicated with nosocomial infections, and high rates of morbidity and mortality, especially in individuals with cystic fibrosis (CF). B. cepacia are naturally resistant to different classes of antibiotics, and can subvert the host innate immune responses by producing quorum sensing (QS) controlled virulence factors and biofilms. It still remains a conundrum as to how exactly the bacterium survives the intracellular environment within the host cells of CF patients and immunocompromised individuals although the bacterium can invade human lung epithelial cells, neutrophils, and murine macrophages. The mechanisms associated with intracellular survival in the airway epithelial cells and the role of QS and virulence factors in B. cepacia infections in cystic fibrosis remain largely unclear. The current review focuses on understanding the role of QS-controlled virulence factors and biofilms, and provides additional impetus to understanding the potentials of QS-inhibitory strategies against B. cepacia.

Loss of O-Linked Protein Glycosylation in Burkholderia cenocepacia Impairs Biofilm Formation and Siderophore Activity and Alters Transcriptional Regulators

O-linked protein glycosylation is a conserved feature of the Burkholderia genus. The addition of the trisaccharide β-Gal-(1,3)-α-GalNAc-(1,3)-β-GalNAc to membrane exported proteins in Burkholderia cenocepacia is required for bacterial fitness and resistance to environmental stress. However, the underlying causes of the defects observed in the absence of glycosylation are unclear. Using proteomics, luciferase reporter assays, and DNA cross-linking, we demonstrate the loss of glycosylation leads to changes in transcriptional regulation of multiple proteins, including the repression of the master quorum CepR/I. These proteomic and transcriptional alterations lead to the abolition of biofilm formation and defects in siderophore activity. Surprisingly, the abundance of most of the known glycosylated proteins did not significantly change in the glycosylation-defective mutants, except for BCAL1086 and BCAL2974, which were found in reduced amounts, suggesting they could be degraded. However, the loss of these two proteins was not responsible for driving the proteomic alterations, biofilm formation, or siderophore activity. Together, our results show that loss of glycosylation in B. cenocepacia results in a global cell reprogramming via alteration of the transcriptional regulatory systems, which cannot be explained by the abundance changes in known B. cenocepacia glycoproteins.IMPORTANCE Protein glycosylation is increasingly recognized as a common posttranslational protein modification in bacterial species. Despite this commonality, our understanding of the role of most glycosylation systems in bacterial physiology and pathogenesis is incomplete. In this work, we investigated the effect of the disruption of O-linked glycosylation in the opportunistic pathogen Burkholderia cenocepacia using a combination of proteomic, molecular, and phenotypic assays. We find that in contrast to recent findings on the N-linked glycosylation systems of Campylobacter jejuni, O-linked glycosylation does not appear to play a role in proteome stabilization of most glycoproteins. Our results reveal that loss of glycosylation in B. cenocepacia strains leads to global proteome and transcriptional changes, including the repression of the quorum-sensing regulator cepR (BCAM1868) gene. These alterations lead to dramatic phenotypic changes in glycosylation-null strains, which are paralleled by both global proteomic and transcriptional alterations, which do not appear to directly result from the loss of glycosylation per se. This research unravels the pleiotropic effects of O-linked glycosylation in B. cenocepacia, demonstrating that its loss does not simply affect the stability of the glycoproteome, but also interferes with transcription and the broader proteome.

Chronic Azithromycin Use in Cystic Fibrosis and Risk of Treatment-Emergent Respiratory Pathogens

RATIONALE

Azithromycin has been shown to improve lung function and reduce the number of pulmonary exacerbations in patients with cystic fibrosis. Concerns remain, however, regarding the potential emergence of treatment-related respiratory pathogens.

OBJECTIVES

To determine whether chronic azithromycin use (defined as three-times weekly administration) is associated with increased rates of detection of eight specific respiratory pathogens.

METHODS

We performed a new-user, propensity score-matched retrospective cohort study utilizing data from the Cystic Fibrosis Foundation Patient Registry. Incident azithromycin users were propensity score matched 1:1 with contemporaneous nonusers. Kaplan-Meier curves and Cox proportional hazards regression were used to evaluate the association between chronic azithromycin use and incident respiratory pathogen detection. Analyses were performed separately for each pathogen, limited to patients among whom that pathogen had not been isolated in the 2 years before cohort entry.

RESULTS

After propensity score matching, the mean age of the cohorts was approximately 12 years. Chronic azithromycin users had a significantly lower risk of detection of new methicillin-resistant Staphylococcus aureus, nontuberculous mycobacteria, and Burkholderia cepacia complex compared with nonusers. The risk of acquiring the remaining five pathogens was not significantly different between users and nonusers.

CONCLUSIONS

Using an innovative new-user, propensity score-matched study design to minimize indication and selection biases, we found in a predominantly pediatric cohort that chronic azithromycin users had a lower risk of acquiring several cystic fibrosis-related respiratory pathogens. These results may ease concerns that chronic azithromycin exposure increases the risk of acquiring new respiratory pathogens among pediatric patients with cystic fibrosis.

Upper versus lower airway microbiome and metagenome in children with cystic fibrosis and their correlation with lung inflammation

Objective

Airways of children with cystic fibrosis (CF) harbor complex polymicrobial communities which correlates with pulmonary disease progression and use of antibiotics. Throat swabs are widely used in young CF children as a surrogate to detect potentially pathogenic microorganisms in lower airways. However, the relationship between upper and lower airway microbial communities remains poorly understood. This study aims to determine (1) to what extent oropharyngeal microbiome resembles the lung microbiome in CF children and (2) if lung microbiome composition correlates with airway inflammation.

Method

Throat swabs and bronchoalveolar lavage (BAL) were obtained concurrently from 21 CF children and 26 disease controls. Oropharyngeal and lung microbiota were analyzed using 16S rRNA deep sequencing and correlated with neutrophil counts in BAL and antibiotic exposure.

Results

Oropharyngeal microbial communities clustered separately from lung communities and had higher microbial diversity (p < 0.001). CF microbiome differed significantly from non-CF controls, with a higher abundance of Proteobacteria in both upper and lower CF airways. Neutrophil count in the BAL correlated negatively with the diversity but not richness of the lung microbiome. In CF children, microbial genes involved in bacterial motility proteins, two-component system, flagella assembly, and secretion system were enriched in both oropharyngeal and lung microbiome, whereas genes associated with synthesis and metabolism of nucleic acids and protein dominated the non-CF controls.

Conclusions

This study identified a unique microbial profile with altered microbial diversity and metabolic functions in CF airways which is significantly affected by airway inflammation. These results highlight the limitations of using throat swabs as a surrogate to study lower airway microbiome and metagenome in CF children.

Multidrug-resistant Gram-negative bacterial infections in solid organ transplant recipients-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of infections due to multidrug-resistant (MDR) Gram-negative bacilli in the pre- and post-transplant period. MDR Gram-negative bacilli, including carbapenem-resistant Enterobacteriaceae, MDR Pseudomonas aeruginosa, and carbapenem-resistant Acinetobacter baumannii, remain a threat to successful organ transplantation. Clinicians now have access to at least five novel agents with activity against some of these organisms, with others in the advanced stages of clinical development. No agent, however, provides universal and predictable activity against any of these pathogens, and very little is available to treat infections with MDR nonfermenting Gram-negative bacilli including A baumannii. Despite advances, empiric antibiotics should be tailored to local microbiology and targeted regimens should be tailored to susceptibilities. Source control remains an important part of the therapeutic armamentarium. Morbidity and mortality associated with infections due to MDR Gram-negative organisms remain unacceptably high. Heightened infection control and antimicrobial stewardship initiatives are needed to prevent these infections, curtail their transmission, and limit the evolution of MDR Gram-negative pathogens, especially in the setting of organ transplantation.

The Lung Microbiome and Its Role in Pneumonia

The use of next-generation sequencing and multiomic analysis reveals new insights on the identity of microbes in the lower airways blurring the lines between commensals and pathogens. Microbes are not found in isolation; rather they form complex metacommunities where microbe-host and microbe-microbe interactions play important roles on the host susceptibility to pathogens. In addition, the lower airway microbiota exert significant effects on host immune tone. Thus, this review highlights the roles that microbes in the respiratory tract play in the development of pneumonia.

Predicting disease progression in cystic fibrosis

INTRODUCTION

Progressive lung disease is the major cause of morbidity and mortality in patients with cystic fibrosis (CF). Methods of correctly predicting the future progression of lung disease in patients with CF are essential for directing aggressive treatment to prevent loss of lung function and end stage respiratory failure. Areas covered: This review addresses predictors of respiratory disease progression in patients with CF. We searched Web of Science and Medline, with no restriction on publication date, with the search terms 'cystic fibrosis' and 'disease progression', 'lung function decline', 'prognosis', 'prediction/predictive', 'prediction/prognostic scores', 'risk factors', 'outcome measures/endpoints/disease surrogate', 'longitudinal/long term', 'statistical model', and 'survival'. Expert commentary: Forced expiratory volume in 1 sec (FEV₁) and rate of FEV₁ decline, remain the most significant predictors of mortality in patients with CF while CT scores and airway secretion biomarkers are the main predictors of early CF lung disease. Comprehensive scores incorporating clinical, lung function, imaging and laboratory data will become essential in the future for predicting disease progression and for use in clinical trials. Early interventions may delay the progression of structural lung disease.

Sputum microbiota is predictive of long-term clinical outcomes in young adults with cystic fibrosis

BACKGROUND

Complex polymicrobial communities infect cystic fibrosis (CF) lower airways. Generally, communities with low diversity, dominated by classical CF pathogens, associate with worsened patient status at sample collection. However, it is not known if the microbiome can predict future outcomes. We sought to determine if the microbiome could be adapted as a biomarker for patient prognostication.

METHODS

We retrospectively assessed prospectively collected sputum from a cohort of 104 individuals aged 18-22 to determine factors associated with progression to early end-stage lung disease (eESLD; death/transplantation <25 years) and rapid pulmonary function decline (>-3%/year FEV₁ over the ensuing 5 years). Illumina MiSeq paired-end sequencing of the V3-V4 region of the 16S rRNA was used to define the airway microbiome.

RESULTS

Based on the primary outcome analysed, 17 individuals (16%) subsequently progressed to eESLD. They were more likely to have sputum with low alpha diversity, dominated by specific pathogens including Pseudomonas. Communities with abundant Streptococcus were observed to be protective. Microbial communities clustered together by baseline lung disease stage and subsequent progression to eESLD. Multivariable analysis identified baseline lung function and alpha diversity as independent predictors of eESLD. For the secondary outcomes, 58 and 47 patients were classified as rapid progressors based on absolute and relative definitions of lung function decline, respectively. Patients with low alpha diversity were similarly more likely to be classified as experiencing rapid lung function decline over the ensuing 5 years when adjusted for baseline lung function.

CONCLUSIONS

We observed that the diversity of microbial communities in CF airways is predictive of progression to eESLD and disproportionate lung function decline and may therefore represent a novel biomarker.

Risk of Bacterial Transmission in Bronchiectasis Outpatient Clinics

Purpose of Review

The purpose of this review is to discuss the risk of bacterial cross-infection for bronchiectasis patients in the outpatient setting. Cross-infection has primarily been a matter of concern in cystic fibrosis (CF). There is considerable evidence of transmission of pathogens between CF patients, and this has led to guideline recommendations advocating strict segregation policies. Guidelines in bronchiectasis do not specifically address the issue of cross-infection. If cross-infection is prevalent, it may have significant implications for patients and the practical running of specialist care.

Recent Findings

Multiple UK-based studies have now published evidence of cross-infection with Pseudomonas aeruginosa within cohorts of bronchiectasis patients; however, the risk does not appear to be high. There is also evidence suggesting cross-infection from CF patients to bronchiectasis patients.

Summary

The current evidence for cross-infection in bronchiectasis is limited, but suggests a small risk with Pseudomonas aeruginosa. Longitudinal studies looking at Pseudomonas aeruginosa and other pathogens are now required.

Implementation of a successful eradication protocol for Burkholderia Cepacia complex in cystic fibrosis patients

Background

Infection with Burkholderia cepacia complex (Bcc) results in a heterogeneous clinical course ranging from asymptomatic colonization of the airways to fulminant respiratory failure in patients with cystic fibrosis (CF). Early eradication of Pseudomonas aeruginosa improves clinical outcomes. The efficacy and clinical outcomes following implementation of an eradication protocol for Bcc are less well understood.

Methods

We developed and implemented a single center Bcc eradication protocol that included an intensive combination of intravenous, inhaled, and oral antibiotic therapies based on in vitro sensitivities. We conducted a retrospective cohort analysis of clinical outcomes compared to patients with chronic Bcc infection.

Results

Six patients were identified as having a newly acquired Bcc colonization and were placed on the eradication protocol. Sequential sputum samples after completion of the protocol demonstrated sustained clearance of Bcc in all patients. Lung function and nutritional status remained stable in the year following eradication.

Conclusion

Clearance of Bcc from sputum cultures using a standardized protocol was successful at one year and was associated with clinical stability.

Common clinical features of CF (respiratory disease and exocrine pancreatic insufficiency)

First described as a disease of the pancreas, cystic fibrosis is a genetically inherited progressive disease affecting multiple organ systems. Pulmonary and pancreatic involvement is common in individuals with cystic fibrosis, and the former is attributable to most of the mortality that occurs with the condition. This chapter provides an overview of a clinical approach to the pulmonary and pancreatic manifestations of cystic fibrosis.

Factors associated with reduced FEV1 in adult patients with cystic fibrosis in a relatively affluent area

Data collected on adult cystic fibrosis (CF) patients and entered onto the CF database in the south and west regions of England were analysed for the year 2001. FEV1 was taken as a marker of lung disease severity. Data on 371 patients (158 female) mean age 24.7 years (range 16.0-48.9) were assessed. FEV1 was reduced in CF patients infected with Pseudomonas aeruginosa (Pa) (mean 62.6% predicted) compared with those without (mean FEV1 77.8%, P < 0.00001). The reduction was noted irrespective of age group. FEV1 progressively reduced with the increasing need for high-intensity treatment (P < 0.00001) and with the diagnosis of diabetes mellitus (P = 0.03). FEV, correlated with body mass index (BMI) (r = + 0.42, P < 0.0001). Genetic profile and poverty and deprivation score did not affect the value of FEV1. Chronic infection with Pa mainly in young adults, treatment intensity, diabetes mellitus and reduced body mass index are associated with reduced FEV, in adult patients with cystic fibrosis in the south and west regions of England. In this relatively affluent area, scores of poverty and deprivation were not associated with the decline in lung function tests.

Burkholderia cepacia complex in Serbian patients with cystic fibrosis: prevalence and molecular epidemiology

The Burkholderia cepacia complex (Bcc) organisms remain significant pathogens in patients with cystic fibrosis (CF). This study was performed to evaluate the prevalence, epidemiological characteristics, and presence of molecular markers associated with virulence and transmissibility of the Bcc strains in the National CF Centre in Belgrade, Serbia. The Bcc isolates collected during the four-year study period (2010-2013) were further examined by 16 s rRNA gene, pulsed-field gel electrophoresis of genomic DNA, multilocus sequence typing analysis, and phylogenetic analysis based on concatenated sequence of seven alleles. Fifty out of 184 patients (27.2 %) were colonized with two Bcc species, B. cenocepacia (n = 49) and B. stabilis (n = 1). Thirty-four patients (18.5 %) had chronic colonization. Typing methods revealed a high level of similarity among Bcc isolates, indicating a person-to-person transmission or acquisition from a common source. New sequence types (STs) were identified, and none of the STs with an international distribution were found. One centre-specific ST, B. cenocepacia ST856, was highly dominant and shared by 48/50 (96 %) patients colonized by Bcc. This clone was characterized by PCR positivity for both the B. cepacia epidemic strain marker and cable pilin, and showed close genetic relatedness to the epidemic strain CZ1 (ST32). These results indicate that the impact of Bcc on airway colonization in the Serbian CF population is high and virtually exclusively limited to a single clone of B. cenocepacia. The presence of a highly transmissible clone and probable patient-to-patient spread was observed.

Physiotherapy for cystic fibrosis in Australia and New Zealand: A clinical practice guideline

Physiotherapy management is a key element of care for people with cystic fibrosis (CF) throughout the lifespan. Although considerable evidence exists to support physiotherapy management of CF, there is documented variation in practice. The aim of this guideline is to optimize the physiotherapy management of people with CF in Australia and New Zealand. A systematic review of the literature in key areas of physiotherapy practice for CF was undertaken. Recommendations were formulated based on National Health and Medical Research Council (Australia) guidelines and considered the quality, quantity and level of the evidence; the consistency of the body of evidence; the likely clinical impact; and applicability to physiotherapy practice in Australia and New Zealand. A total of 30 recommendations were made for airway clearance therapy, inhalation therapy, exercise assessment and training, musculoskeletal management, management of urinary incontinence, managing the newly diagnosed patient with CF, delivery of non-invasive ventilation, and physiotherapy management before and after lung transplantation. These recommendations can be used to underpin the provision of evidence-based physiotherapy care to people with CF in Australia and New Zealand.

Two case reports of the successful eradication of new isolates of Burkholderia cepacia complex in children with cystic fibrosis

Background

Chronic infection with Burkholderia cepacia complex (BCC) has a detrimental effect on morbidity and mortality for patients with cystic fibrosis (CF). It is therefore logical to attempt to eradicate new isolates however there is a paucity of information to guide treatment. We report the successful eradication of new isolates of BCC in two children with CF.

Case presentation

Burkholderia cepacia was successfully eradicated in a 14 year old boy with CF and Burkholderia gladioli was successfully eradicated in a six year old girl with CF. In both children two weeks of intravenous (IV) tobramycin, ceftazidime and temocillin were used followed by three months of inhaled tobramycin. Bronchoalveolar lavage samples taken during flexible bronchoscopy were used prior to treatment to exclude spontaneous clearance as well as after treatment to confirm eradication.

Conclusions

New isolates of BCC can be successfully eradicated in children with CF. More research is urgently required in this area to identify the best treatment regimen for BCC eradication.

Assessing Differences in Mortality Rates and Risk Factors Between Hispanic and Non-Hispanic Patients With Cystic Fibrosis in California

BACKGROUND

Over the past 30 years, therapeutic advances have extended the median lifespan of patients with cystic fibrosis (CF). Hispanic patients are a vulnerable subpopulation with a high prevalence of risk factors for worse health outcomes. The consequences of these differences on health outcomes have not been well described. The objective of this study was to characterize the difference in health outcomes, including mortality rate, between Hispanic and non-Hispanic patients with CF.

METHODS

This study is a retrospective analysis of CF Foundation Patient Registry data of California residents with CF, diagnosed during or after 1991, from 1991 to 2010. Ethnicity was self-reported. The primary outcome was mortality. Hazard ratios were estimated from a Cox regression model, stratified by sex, and adjusted for socioeconomic status, clinical risk factors, and year of diagnosis.

RESULTS

Of 1,719 patients, 485 (28.2%) self-identified as Hispanic. Eighty-five deaths occurred, with an overall mortality rate of 4.9%. The unadjusted mortality rate was higher among Hispanic patients than among non-Hispanic patients (9.1% vs 3.3%, P < .0001). Compared with non-Hispanic patients, Hispanic patients had a lower survival rate 18 years after diagnosis (75.9% vs 91.5%, P < .0001). Adjusted for socioeconomic status and clinical risk factors, Hispanic patients had an increased rate of death compared with non-Hispanic patients (hazard ratio, 2.81; 95% CI, 1.70-4.63).

CONCLUSIONS

Hispanic patients with CF have a higher mortality rate than do non-Hispanic patients, even after adjusting for socioeconomic status and clinical severity. Further investigation into the mechanism for the measured difference in lung function will help inform interventions and improve the health of all patients with CF.

Cystic fibrosis

Cystic fibrosis is an autosomal recessive, monogenetic disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The gene defect was first described 25 years ago and much progress has been made since then in our understanding of how CFTR mutations cause disease and how this can be addressed therapeutically. CFTR is a transmembrane protein that transports ions across the surface of epithelial cells. CFTR dysfunction affects many organs; however, lung disease is responsible for the vast majority of morbidity and mortality in patients with cystic fibrosis. Prenatal diagnostics, newborn screening and new treatment algorithms are changing the incidence and the prevalence of the disease. Until recently, the standard of care in cystic fibrosis treatment focused on preventing and treating complications of the disease; now, novel treatment strategies directly targeting the ion channel abnormality are becoming available and it will be important to evaluate how these treatments affect disease progression and the quality of life of patients. In this Primer, we summarize the current knowledge, and provide an outlook on how cystic fibrosis clinical care and research will be affected by new knowledge and therapeutic options in the near future. For an illustrated summary of this Primer, visit: http://go.nature.com/4VrefN.

Clinical applications of pulmonary delivery of antibiotics

The treatment of infection typically involves administration of antibiotics by a systemic route, such as intravenous or oral. However, pulmonary infections can also be approached by inhalation of antibiotics as the infection is more directly accessible via the airways, making inhalation delivery essentially topical administration. This approach offers deposition of high antimicrobial concentrations directly at the site of infection but with a potentially reduced systemic exposure. This review covers the evidence for aerosolized antibiotics for the treatment of a number of conditions such as cystic fibrosis (CF), where it has become the standard of care for chronic infection, as well as non-CF bronchiectasis, non-tuberculous mycobacteria, and ventilator-associated infection where such therapy does not have an approved indication but has been used with increasing frequency.

Lung transplantation for cystic fibrosis: results, indications, complications, and controversies

Survival in patients with cystic fibrosis (CF) has improved dramatically over the past 30 to 40 years, with mean survival now approximately 40 years. Nonetheless, progressive respiratory insufficiency remains the major cause of mortality in CF patients, and lung transplantation (LT) is eventually required. Timing of listing for LT is critical, because up to 25 to 41% of CF patients have died while awaiting LT. Globally, approximately 16.4% of lung transplants are performed in adults with CF. Survival rates for LT recipients with CF are superior to other indications, yet LT is associated with substantial morbidity and mortality (∼50% at 5-year survival rates). Myriad complications of LT include allograft failure (acute or chronic), opportunistic infections, and complications of chronic immunosuppressive medications (including malignancy). Determining which patients are candidates for LT is difficult, and survival benefit remains uncertain. In this review, we discuss when LT should be considered, criteria for identifying candidates, contraindications to LT, results post-LT, and specific complications that may be associated with LT. Infectious complications that may complicate CF (particularly Burkholderia cepacia spp., opportunistic fungi, and nontuberculous mycobacteria) are discussed.

Characterization of BCAM0224, a multifunctional trimeric autotransporter from the human pathogen Burkholderia cenocepacia

Members of the trimeric autotransporter adhesin (TAA) family play a crucial role in adhesion of Gram-negative pathogens to host cells. Moreover, these proteins are multifunctional virulence factors involved in several other biological traits, including invasion into host cells and evasion of the host immune system. In cystic fibrosis epidemic Burkholderia cenocepacia strain J2315, we identified a unique TAA (BCAM0224)-encoding gene, previously described as being implicated in virulence. Here, we characterized this multifunctional protein, trying to establish its role in B. cenocepacia pathogenicity. We show that BCAM0224 occurs on the bacterial surface and adopts a trimeric conformation. Furthermore, we demonstrated that BCAM0224 is needed for earlier stages of biofilm formation and is required for swarming motility. In addition, BCAM0224 plays an important role in evasion of the human innate immune system, providing resistance against the bactericidal activity of serum via the complement classical pathway. Finally, BCAM0224 mediates bacterial adhesion to and invasion of cultured human bronchial epithelial cells. Together, these data reveal the high versatility of the BCAM0224 protein as a virulence factor in the pathogenic bacterium B. cenocepacia.

Lung transplantation in patients with cystic fibrosis: special focus to infection and comorbidities

Despite advances in medical care, patients with cystic fibrosis still face limited life expectancy. The most common cause of death remains respiratory failure. End-stage cystic fibrosis can be treated with lung transplantation and is the third most common reason for which the procedure is performed. Outcomes for cystic fibrosis are better than most other lung diseases, but remain limited (5-year survival 60%). For patients with advanced disease lung transplantation appears to improve survival. Outcomes for patients with Burkholderia cepacia remain poor, although they are better for patients with certain genomovars. Controversy exists about Mycobacterium abscessus infection and appropriateness for transplant. More information is also becoming available for comorbidities, including diabetes and pulmonary hypertension among others. Extra-corporeal membrane oxygenation is used more frequently for end-stage disease as a bridge to lung transplantation and will likely be used more in the future.

Regulation and functional significance of autophagy in respiratory cell biology and disease

Autophagy is a homeostatic process common to all eukaryotic cells that serves to degrade intracellular components. Among three classes of autophagy, macroautophagy is best understood, and is the subject of this Review. The function of autophagy is multifaceted, and includes removal of long-lived proteins and damaged or unneeded organelles, recycling of intracellular components for nutrients, and defense against pathogens. This process has been extensively studied in yeast, and understanding of its functional significance in human disease is also increasing. This Review explores the basic machinery and regulation of autophagy in mammalian systems, methods employed to measure autophagic activity, and then focuses on recent discoveries about the functional significance of autophagy in respiratory diseases, including chronic obstructive pulmonary disease, cystic fibrosis, tuberculosis, idiopathic pulmonary fibrosis, pulmonary arterial hypertension, acute lung injury, and lymphangioleiomyomatosis.

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.

Nongenetic influences on cystic fibrosis outcomes

PURPOSE OF REVIEW

Despite dramatic improvements over the last several decades, tremendous variation exists in cystic fibrosis (CF) health outcomes. Genetic explanations for variations in disease progression are a promising source of information regarding disease biology and pathophysiology, but an understanding of nongenetic factors provides more immediate tools for improving disease outcomes.

RECENT FINDINGS

The clinical course of CF for any individual with CF is determined by the interaction of genetic endowment (including CFTR and modifier genes), the physical environment (including environmental tobacco smoke, outdoor pollution, and pathogenic microorganisms), the sociodemographic, cultural, and family context (which mediates stress, social support, and disease self-management skills), and variations in delivery and acceptance of healthcare treatments. The evidence linking socioeconomic status (SES) with CF outcomes continues to be strong, and appears to be primarily due to associations with environmental and sociocultural stressors and disease-management behaviors rather than barriers in access to healthcare.

SUMMARY

Attempts to eliminate detrimental environmental exposures, improve disease self-management skills, and ensure consistently optimal healthcare practices will likely decrease variations in outcomes including SES-related disparities. Low SES is an important marker of adverse exposures and outcomes which are present throughout the CF population.

Autophagy stimulation by rapamycin suppresses lung inflammation and infection by Burkholderia cenocepacia in a model of cystic fibrosis

Cystic fibrosis (CF) is the most common inherited lethal disease of Caucasians which results in multi organ dysfunction. However, 85% of the deaths are due to pulmonary infections. Infection by Burkholderia cenocepacia (B. cepacia) is a particularly lethal threat to CF patients because it causes severe and persistent lung inflammation and is resistant to nearly all available antibiotics. In CFTR ΔF508 mouse macrophages, B. cepacia persists in vacuoles that do not fuse with the lysosomes and mediates increased production of IL-1β. It is believed that intracellular bacterial survival contributes to the persistence of the bacterium. Here we show for the first time that in wild-type macrophages but not in ΔF508 macrophages, many B. cepacia reside in autophagosomes that fuse with lysosomes at later stages of infection. Accordingly, association and intracellular survival of B. cepacia are higher in CFTR-ΔF508 (ΔF508) macrophages than in WT macrophages. An autophagosome is a compartment that engulfs non-functional organelles and parts of the cytoplasm then delivers them to the lysosome for degradation to produce nutrients during periods of starvation or stress. Furthermore, we show that B. cepacia downregulates autophagy genes in WT and ΔF508 macrophages. However, autophagy dysfunction is more pronounced in ΔF508 macrophages since they already have compromised autophagy activity. We demonstrate that the autophagy-stimulating agent, rapamycin markedly decreases B. cepacia infection in vitro by enhancing the clearance of B. cepacia via induced autophagy. In vivo, Rapamycin decreases bacterial burden in the lungs of CF mice and drastically reduces signs of lung inflammation. Together, our studies reveal that if efficiently activated, autophagy can control B. cepacia infection and ameliorate the associated inflammation. Therefore, autophagy is a novel target for new drug development for CF patients to control B. cepacia infection and accompanying inflammation.

Burkholderia cepacia complex: beyond pseudomonas and acinetobacter

Burkholderia cepacia complex (BCC) is an important nosocomial pathogen in hospitalised patients, particularly those with prior broad-spectrum antibacterial therapy. BCC causes infections that include bacteraemia, urinary tract infection, septic arthritis, peritonitis and respiratory tract infection. Due to high intrinsic resistance and being one of the most antimicrobial-resistant organisms encountered in the clinical laboratory, these infections can prove very difficult to treat and, in some cases, result in death. Patients with cystic fibrosis (CF) and those with chronic granulomatous disease are predisposed to infection by BCC bacteria. BCC survives and multiplies in aqueous hospital environments, including disinfectant agents and intravenous fluids, where it may persist for long periods. Outbreaks and pseudo-outbreaks of BCC septicaemia have been documented in intensive care units, oncology units and renal failure patients. BCC is phenotypically unremarkable, and the complex exhibits an extensive diversity of genotypes. BCC is of increasing importance for agriculture and bioremediation because of their antinematodal and antifungal properties as well as their capability to degrade a wide range of toxic compounds. It has always been a tedious task for a routine microbiological laboratory to identify the nonfermenting gram-negative bacilli, and poor laboratory proficiency in identification of this nonfermenter worldwide still prevails. In India, there are no precise reports of the prevalence of BCC infection, and in most cases, these bacteria have been ambiguously reported as nonfermenting gram-negative bacilli or simply Pseudomonas spp. The International Burkholderia cepacia Working Group is open to clinicians and scientists interested in advancing knowledge of BCC infection/colonisation in persons with CF through the collegial exchange of information and promotion of coordinated approaches to research.

Clinical significance of microbial infection and adaptation in cystic fibrosis

A select group of microorganisms inhabit the airways of individuals with cystic fibrosis. Once established within the pulmonary environment in these patients, many of these microbes adapt by altering aspects of their structure and physiology. Some of these microbes and adaptations are associated with more rapid deterioration in lung function and overall clinical status, whereas others appear to have little effect. Here we review current evidence supporting or refuting a role for the different microbes and their adaptations in contributing to poor clinical outcomes in cystic fibrosis.

Impact of mannose-binding lectin insufficiency on the course of cystic fibrosis: A review and meta-analysis

Mannose-binding lectin (MBL) is an innate immune protein produced by the liver. MBL binds to glycoconjugates containing mannose, fucose or N-acetylglucosamine that are present in a wide variety of bacteria, viruses and fungi. Upon binding, MBL may active the lectin pathway of complement or directly opsonize organisms to enhance phagocytosis. MBL is primarily a serum protein but accumulates in the lung during acute inflammation. Recent evidence suggests an important role for MBL in a variety of infectious disorders. Cystic fibrosis (CF) is a multisystem disease caused by mutations in the gene encoding the CF transmembrane regulator (CFTR). The course of CF lung disease is highly variable even in patients with the same CFTR genotype, suggesting that other modulator genes are important for prognosis. MBL has been proposed as a possible modulator of clinical severity in CF. In this review and meta-analysis, we found that MBL2 genotypes associated with MBL insufficiency were associated with earlier acquisition of Pseudomonas aeruginosa (P < 0.0001), reduced pulmonary function among adult patients (P < 0.0001 for forced expiratory volume), and an increased rate of death or requirement for lung transplantation (odds ratio 3.69; P = 0.02). The available evidence therefore suggests that MBL insufficiency is associated with the severity of CF lung disease. The possible future prophylactic or therapeutic application of MBL replacement is discussed.

Gender differences in the Scandinavian cystic fibrosis population

AIMS

To explore whether gender differences in the Scandinavian Cystic Fibrosis (CF) patients exist in the areas of key clinical parameters, complications, and medication.

METHODS

Cross-sectional data on 890 (416 female) pancreatic insufficient CF patients were evaluated regarding chronic infection, body mass index, lung function, medication, and diabetes, as well as data of Pseudomonas infection status, antibiotic treatment and hospitalization from 1-year follow-up.

RESULTS

We found no differences in lung function, body mass index, or frequency of diabetes. The adult group consisted of more males than females (208:168). We found no significant difference in prevalence of chronic Pseudomonas aeruginosa infection, but during the follow-up the incidence of new chronic infection was higher in adult females (10/33 vs. 4/56). Females had higher prevalence of Burkholderia infection (21/416 vs. 11/474). Adult females had more days on intravenous antibiotics (median 39 vs. 26 days/year), and days in hospital (median 2 vs. 0 days/year). More adult females received inhaled and oral steroids. In the pediatric cohort, females were treated more often with macrolides as an anti-inflammatory agent.

CONCLUSION

We found no gender difference in key clinical parameters in our CF population. However, our study showed a higher risk of Pseudomonas and Burkholderia infection among the female patients. Additionally, we found that female patients require more intensified treatment regarding antibiotics, macrolides, steroids and days of hospitalization, indicating a true female disadvantage even with modern aggressive treatment. The finding of more males than females in the adult population suggesting a male advantage, warrants a mortality study.

Role of bacteriocins in mediating interactions of bacterial isolates taken from cystic fibrosis patients

Pseudomonas aeruginosa (Pa) and Burkholderia cepacia complex (Bcc) lung infections are responsible for much of the mortality in cystic fibrosis (CF). However, little is known about the ecological interactions between these two, often co-infecting, species. This study provides what is believed to be the first report of the intra- and interspecies bacteriocin-like inhibition potential of Pa and Bcc strains recovered from CF patients. A total of 66 strains were screened, and shown to possess bacteriocin-like inhibitory activity (97 % of Pa strains and 68 % of Bcc strains showed inhibitory activity), much of which acted across species boundaries. Further phenotypic and molecular-based assays revealed that the source of this inhibition differs for the two species. In Pa, much of the inhibitory activity is due to the well-known S and RF pyocins. In contrast, Bcc inhibition is due to unknown mechanisms, although RF-like toxins were implicated in some strains. These data suggest that bacteriocin-based inhibition may play a role in governing Pa and Bcc interactions in the CF lung and may, therefore, offer a novel approach to mediating these often fatal infections.

Pediatric lung transplantation

Lung transplantation is an accepted therapy for selected pediatric patients with severe end-stage vascular or parenchymal lung disease. Collaboration between the patients' primary care physicians, the lung transplant team, patients, and patients' families is essential. The challenges of this treatment include the limited availability of suitable donor organs, the toxicity of immunosuppressive medications needed to prevent rejection, the prevention and treatment of obliterative bronchiolitis, and maximizing growth, development, and quality of life of the recipients. This article describes the current status of pediatric lung transplantation, indications for listing, evaluation of recipient and donor, updates on the operative procedure,graft dysfunction, and the risk factors, outcomes, and future directions.

Susceptibility of Caenorhabditis elegans to Burkholderia infection depends on prior diet and secreted bacterial attractants

The nematode Caenorhabditis elegans may be killed by certain pathogenic bacteria and thus is a model organism for studying interactions between bacteria and animal hosts. However, growing nematodes on prey bacteria may influence their susceptibility to potential pathogens. A method of axenic nematode culture was developed to isolate and quantify interactions between C. elegans and potentially pathogenic strains of the Burkholderia cepacia complex. Studying these dynamics in liquid solution rather than on agar surfaces minimized nematode avoidance behavior and resolved more differences among isolates. Most isolates of B. cenocepacia, B. ambifaria and B. cepacia caused 60–80% mortality of nematodes after 7 days, whereas isolates of B. multivorans caused less mortality (<25%) and supported nematode reproduction. However, some B. cenocepacia isolates recovered from chronic infections were much less virulent (5–28% mortality). As predicted, prior diet altered the outcome of interactions between nematodes and bacteria. When given the choice between Burkholderia and E. coli as prey on agar, axenically raised nematodes initially preferred most lethal Burkholderia isolates to E. coli as a food source, but this was not the case for nematodes fed E. coli, which avoided toxic Burkholderia. This food preference was associated with the cell-free supernatant and thus secreted compounds likely mediated bacterial-nematode interactions. This model, which isolates interactions between bacteria and nematodes from the effects of prior feeding, demonstrates that bacteria can influence nematode behavior and their susceptibility to pathogens.

A type IV secretion system contributes to intracellular survival and replication of Burkholderia cenocepacia

Burkholderia cenocepacia is an important respiratory pathogen in persons with cystic fibrosis (CF). Recent studies indicate that B. cenocepacia survives within macrophages and airway epithelial cells in vitro by evading endosome-lysosome fusion. We investigated the role of a plasmid-encoded type IV secretion system in the intracellular survival, replication, and processing of B. cenocepacia. Both a wild-type strain (K56-2) and its type IV secretion system mutant (designated LC101) entered and replicated in CF airway epithelial cells and monocyte-derived macrophages. However, significantly more intracellular K56-2 than LC101 bacteria were found in both cell types at 24 h postinfection. Colocalization of bacteria with markers of the classical endocytic pathway indicated that although both K56-2 and LC101 reside transiently in early endosomes, a greater proportion of the mutant bacteria are targeted to lysosomal degradation. In contrast, wild-type bacteria escape from the classical endocytic pathway and traffic to the endoplasmic reticulum, where they replicate. Our results show that the intracellular processing of B. cenocepacia is similar in both professional and nonprofessional phagocytes and that a functional plasmid-encoded type IV secretion system contributes to the survival and replication of B. cenocepacia in eukaryotic cells.

Survival after lung transplantation of cystic fibrosis patients infected with Burkholderia cepacia complex

Within the Burkholderia cepacia complex (Bcc), B. cenocepacia portends increased mortality compared with other species. We investigated the impact of Bcc infection on mortality and re-infection following lung transplant (LT). Species designation for isolates from Bcc-infected patients was determined using 16S rDNA and recA gene analyses. Of 75 cystic fibrosis patients undergoing LT from September 1992 to August 2002, 59 had no Bcc and 16 had Bcc (including 7 B. cenocepacia) isolated in the year before LT. Of the latter, 87.5% had Bcc recovered after transplantation, and all retained their pretransplant strains. Survival was 97%, 92%, 76% and 63% for noninfected patients; 89%, 89%, 67% and 56% for patients infected with Bcc species other than B. cenocepacia; and 71%, 29%, 29% and 29% for patients with B. cenocepacia (p = 0.014) at 1 month, 1 year, 3 years and 5 years, respectively. Patients infected with B. cenocepacia before transplant were six times more likely to die within 1 year of transplant than those infected with other Bcc species (p = 0.04) and eight times than noninfected patients (p < 0.00005). Following LT, infection with Bcc species other than B. cenocepacia does not significantly impact 5-year survival whereas infection with B. cenocepacia pretransplant is associated with decreased survival.

Burkholderia cenocepacia C5424 produces a pigment with antioxidant properties using a homogentisate intermediate

Burkholderia cenocepacia is a gram-negative opportunistic pathogen that belongs to the Burkholderia cepacia complex. B. cenocepacia can survive intracellularly within phagocytic cells, and some epidemic strains produce a brown melanin-like pigment that can scavenge free radicals, resulting in the attenuation of the host cell oxidative burst. In this work, we demonstrate that the brown pigment produced by B. cenocepacia C5424 is synthesized from a homogentisate (HGA) precursor. The disruption of BCAL0207 (hppD) by insertional inactivation resulted in loss of pigmentation. Steady-state kinetic analysis of the BCAL0207 gene product demonstrated that it has 4-hydroxyphenylpyruvic acid dioxygenase (HppD) activity. Pigmentation could be restored by complementation providing hppD in trans. The hppD mutant was resistant to paraquat challenge but sensitive to H2O2 and to extracellularly generated superoxide anions. Infection experiments in RAW 264.7 murine macrophages showed that the nonpigmented bacteria colocalized in a dextran-positive vacuole, suggesting that they are being trafficked to the lysosome. In contrast, the wild-type strain did not localize with dextran. Colocalization of the nonpigmented strain with dextran was reduced in the presence of the NADPH oxidase inhibitor diphenyleneiodonium, and also the inducible nitric oxide inhibitor aminoguanidine. Together, these observations suggest that the brown pigment produced by B. cenocepacia C5424 is a pyomelanin synthesized from an HGA intermediate that is capable of protecting the organism from in vitro and in vivo sources of oxidative stress.

Burkholderia cenocepacia ET12 strain activates TNFR1 signalling in cystic fibrosis airway epithelial cells

Burkholderia cenocepacia is an important pulmonary pathogen in individuals with cystic fibrosis (CF). 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 tumour necrosis factor receptor 1 (TNFR1) and activates TNFR1-related signalling pathway similar to TNF-alpha, a natural ligand for TNFR1. This interaction participates in stimulating a robust IL-8 production from CF airway epithelial cells. In contrast, BC45, a 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 with non-CF cells. We also show that B. cenocepacia ET12 strain colocaizes with TNFR1 in vitro and in the lungs of CF patients 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.

Infection Control Practice in Cystic Fibrosis Centers

In this article, the authors outline some of the major historical events that signaled the need to better understand mechanisms of infection in cystic fibrosis (CF). The authors discuss general principles of infection control, focusing on issues of particular importance to patients who have CF. The authors also describe the major pathogens associated with the CF airway, provide a review of findings from inpatient and outpatient studies of infection control, and provide an outline of future directions for investigation.