Update in cystic fibrosis 2008

Clinical Outcomes Associated With Escherichia coli Infections in Adults With Cystic Fibrosis: A Cohort Study

Background

Analysis of “emerging” pathogens in cystic fibrosis (CF) lung disease has focused on unique pathogens that are rare in other human diseases or are drug resistant. Escherichia coli is recovered in the sputum of up to 25% of patients with CF, yet little is known about the epidemiology or clinical impact of infection.

Methods

We studied patients attending a Canadian adult CF clinic who had positive sputum cultures for E coli from 1978 to 2016. Infection was categorized as transient or persistent (≥3 positive sputum cultures, spanning >6 months). Those with persistent infection were matched 2:1 with age, sex, and time-period controls without history of E coli infection, and mixed-effects models were used to assess pulmonary exacerbation (PEx) frequency, lung function decline, hospitalization, and intravenous antibiotic days.

Results

Forty-five patients (12.3%) had E coli recovered from sputum samples between 1978 and 2016, and 18 patients (40%) developed persistent infection. Nine patients (24%) had PEx at incident infection, and increased bioburden was predictive of exacerbation (P = .03). Risk factors for persistent infection included lower nutritional status (P < .001) and lower lung function (P = .009), but chronic infection with Pseudomonas aeruginosa was protective. There was no difference in annual lung function decline, need for hospitalization or intravenous antibiotics, or risk of PEx in patients with persistent infection.

Conclusions

Persistent E coli infection was frequent and was more common in CF patients with low nutritional status and lung function. However, this does not predict clinical decline. Multicenter studies would allow better characterization of the epidemiology and clinical impact of E coli infection.

Epidemiology, Biology, and Impact of Clonal Pseudomonas aeruginosa Infections in Cystic Fibrosis

Chronic lower airway infection with Pseudomonas aeruginosa is a major contributor to morbidity and mortality in individuals suffering from the genetic disease cystic fibrosis (CF). Whereas it was long presumed that each patient independently acquired unique strains of P. aeruginosa present in their living environment, multiple studies have since demonstrated that shared strains of P. aeruginosa exist among individuals with CF. Many of these shared strains, often referred to as clonal or epidemic strains, can be transmitted from one CF individual to another, potentially reaching epidemic status. Numerous epidemic P. aeruginosa strains have been described from different parts of the world and are often associated with an antibiotic-resistant phenotype. Importantly, infection with these strains often portends a worse prognosis than for infection with nonclonal strains, including an increased pulmonary exacerbation rate, exaggerated lung function decline, and progression to end-stage lung disease. This review describes the global epidemiology of clonal P. aeruginosa strains in CF and summarizes the current literature regarding the underlying biology and clinical impact of globally important CF clones. Mechanisms associated with patient-to-patient transmission are discussed, and best-evidence practices to prevent infections are highlighted. Preventing new infections with epidemic P. aeruginosa strains is of paramount importance in mitigating CF disease progression.

Attitudes Toward Discussing Approved and Investigational Treatments for Cystic Fibrosis in Prenatal Genetic Counseling Practice

This project aimed to explore the attitudes of prenatal genetic counselors toward discussion of novel approved and experimental CF treatments in the prenatal setting, and to assess how knowledge of genotype-specific, targeted treatments may influence their current practices. Targeted treatments have the potential to impact the health-related quality of life of individuals affected with CF and therefore, knowledge of the availability of such treatments may influence the decision-making process of parents who receive a fetal diagnosis of CF. Using the 2012 FDA approval and introduction of ivacaftor into CF clinical practice as a case study, a survey was designed to explore the opinions and practices of prenatal genetic counselors with regard to counseling for a prenatal diagnosis of CF, and how those practices might be impacted by the availability of a new genotype-specific treatment. Approximately 800 genetic counselors were sent questionnaires in January of 2013. Respondents were provided information about this treatment and were asked to rate its perceived benefits, along with the likelihood that they would discuss potential benefits and limitations with parents receiving a prenatal diagnosis of CF. One-hundred sixty-nine prenatal genetic counselors (21.1 %) responded to the survey. Results indicated that 80 % of respondents 'never heard of the drug', or they were 'not exactly sure' what it was. After reading the materials provided, counselors felt the new treatment would have 'some' or a 'significant' impact on an affected individual's life. Their opinions varied on what information about this treatment they would choose to discuss with their patients; even if the treatment is currently FDA approved and clinically available for affected individuals with the genotype of the fetus. However, they would 'definitely' refer these patients to a specialist to discuss targeted treatments further. Most prenatal genetic counselors indicated there are certain scenarios in the prenatal setting which warrant a discussion of targeted treatments for CF, at least on some level. Counselor's views on sharing information about new treatment options are shaped by their familiarity with the treatment and their perception of its benefits and limitations, their comfort discussing these subjects, and their interpretation of the genetic counselor's role. Most genetic counselors had never heard of ivacaftor or Kalydeco™ prior to taking the survey. Therefore, counselors need to be better educated about the availability of CFTR mutation-based treatments before they will be able to incorporate discussion of new treatment options into their counseling.

Tobramycin inhalation powder: an efficient and efficacious therapy for the treatment of Pseudomonas aeruginosa infection in cystic fibrosis

Inhaled antipseudomonal therapies are critical components in the management of cystic fibrosis (CF) and have significantly contributed to improved patient outcomes. Dry powder inhaler technologies represent a significant advance in drug delivery, alleviating treatment burden and potentially improving adherence associated with traditional CF nebulized therapies. Tobramycin inhalation powder (TIP) uses PulmoSphere® technology for very efficient drug delivery into the lower airways. In placebo-controlled and comparative studies with traditional tobramycin formulations, TIP is equally efficacious and is associated with increased patient convenience and satisfaction. TIP has been recommended in the 2013 CF Foundation and the 2014 European guidelines as a therapy in CF for the maintenance of lung health. Going forward, TIP may offer a therapeutic advantage over traditional formulations of tobramycin as recent prospective ‘real world’ studies of TIP have demonstrated high patient tolerance and improved adherence compared with traditional formulations.

Genetic, cell biological, and clinical interrogation of the CFTR mutation c.3700 A>G (p.Ile1234Val) informs strategies for future medical intervention

PURPOSE

The purpose of this study was to determine the molecular consequences of the variant c.3700 A>G in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, a variant that has been predicted to cause a missense mutation in the CFTR protein (p.Ile1234Val).

METHODS

Clinical assays of CFTR function were performed, and genomic DNA from patients homozygous for c.3700 A>G and their family members was sequenced. Total RNA was extracted from epithelial cells of the patients, transcribed into complementary DNA, and sequenced. CFTR complementary DNA clones containing the missense mutation p.Ile1234Val or a truncated exon 19 (p.Ile1234_Arg1239del) were constructed and heterologously expressed to test CFTR protein synthesis and processing.

RESULTS

In vivo functional measurements revealed that the individuals homozygous for the variant c.3700 A>G exhibited defective CFTR function. We show that this mutation in exon 19 activates a cryptic donor splice site 18 bp upstream of the original donor splice site, resulting in deletion of six amino acids (r.3700_3717del; p.Ile1234_Arg1239del). This deletion, similar to p.Phe508del, causes a primary defect in folding and processing. Importantly, Lumacaftor (VX-809), currently in clinical trial for cystic fibrosis patients with the major cystic fibrosis-causing mutation, p.Phe508del, partially ameliorated the processing defect caused by p.Ile1234_Arg1239del.

CONCLUSION

These studies highlight the need to verify molecular and clinical consequences of CFTR variants to define possible therapeutic strategies.

Tobramycin Inhalation Powder (TIP): An Efficient Treatment Strategy for the Management of Chronic Pseudomonas Aeruginosa Infection in Cystic Fibrosis

Repeated bouts of acute and chronic lung infections are responsible for progressive pulmonary function decline in individuals with cystic fibrosis (CF), ultimately leading to respiratory failure and death. Pseudomonas aeruginosa is the archetypical CF pathogen, causes chronic infection in 70% of individuals, and is associated with an accelerated clinical decline. The management of P. aeruginosa in CF has been revolutionized with the development and widespread use of inhaled antibiotics. Aerosol delivery of antimicrobial compounds in CF enables extremely high concentrations of antibiotics to be reached directly at the site of infection potentially overcoming adaptive resistance and avoiding the potential for cumulative systemic toxicities. Tobramycin inhalation powder (TIP) represents the first dry powder inhaled (DPI) antibiotic available for use in CF. DPIs are notable for a markedly reduced time for administration, ease of portability, and increased compliance. TIP has been developed as a therapeutic alternative to tobramycin inhalation solution (TIS), the standard of care for the past 20 years within CF. Relative to TIS 300 mg nebulized twice daily in on-and-off cycles of 28 days duration, TIP 112 mg twice daily via the T-326 inhaler administered on the same schedule is associated with marked time savings, increased patient satisfaction, and comparable clinical end points. TIP represents an innovative treatment strategy for those individuals with CF and holds the promise of increased patient compliance and thus the potential for improved clinical outcomes.

Pulmonary hypertension is a mild comorbidity in end-stage cystic fibrosis patients

BACKGROUND

This study investigated the prevalence of pulmonary hypertension (PH) in cystic fibrosis (CF) patients awaiting lung transplantation (LTx) and its influence on survival. We also explored the feasibility of using echocardiography as a first assessment for diagnosing PH.

METHODS

The study included 93 CF patients (46 women [50%]) evaluated for LTx between 2001 and 2010. Median age was 29 years. PH was defined as a mean pulmonary artery pressure (mPAP) measured by right heart catheterization (mPAP(cath)) of ≥ 25 mm Hg with a wedge pressure of ≤ 15 mm Hg. Echocardiographic results were divided into 3 categories based on current guidelines as "unlikely," "possible," or "likely" to have PH.

RESULTS

In 23 patients (25%) the mPAP(cath) was between 25 and 35 mm Hg, and 1 (1%) had severe PH (mPAP(cath) of ≥ 35 mm Hg). PH did not influence survival after enlistment (p = 0.7) and after LTx (p = 0.8). For 62 patients (67%), the sPAP(echo) could be measured, and PH was unlikely in 24 (39%). In another 19 patients (20%), PH was unlikely based on the absence of tricuspid regurgitation. The negative-predictive value (NPV) of measuring PH by echocardiography was 88% in whom PH was estimated to be unlikely (n = 43); whereas in 24 patients with a measurable low sPAP(echo), the NPV was 96%.

CONCLUSIONS

PH exists in 26% of end-stage CF patients and has no effect on survival on the waiting list for LTx or after LTx. Echocardiography might be used as the first tool to rule out PH, showing a NPV of 88%.

Managing treatment complexity in cystic fibrosis: challenges and opportunities

Cystic fibrosis (CF) is a complex, chronic, multisystem disease for which there is currently no cure. Nonetheless, advances in management have led to dramatic improvements in patient survival. With this development, new issues have arisen for CF patients and their care providers, including an increased symptom burden and increased frequency of co-morbidities as patients reach older ages, leading to the need for a highly complicated and time-consuming regimen of treatments. Such high symptom and treatment burden often leads to non-adherence and low levels of competence with administration of therapy, both of which may have detrimental impacts on CF outcomes. Optimal management is also hindered by other patient-related factors, including inadequacies in disease education which may lead to issues with self-management. This is particularly important during the transition from parent-directed therapy to independent self-management that occurs during adolescence and early adulthood. Clinicians are also faced with a considerable challenge when selecting interventions for individual patients; although the paradigm of aggressive care necessitates a wide range of therapies, there is a limited evidence base with which to compare available therapeutic regimens. Novel pharmacological agents are being developed to target the underlying cause of CF, while non-pharmacological interventions aim to improve competence and maximize adherence and health outcomes. Comparative effectiveness research is needed to simplify management and facilitate the implementation of appropriate treatment strategies.

Aztreonam lysine: a novel inhalational antibiotic for cystic fibrosis

Acquisition of Pseudomonas aeruginosa, the most prevalent organism isolated from cystic fibrosis (CF) airways, is associated with an accelerated clinical deterioration and reduced survival. Strategies to chronically suppress P. aeruginosa infections in individuals with CF have evolved over the last four decades and now largely focus on regular administration of aerosolized antibiotics. Aztreonam lysine (AZLI; Cayston, Gilead Pharmaceuticals [Foster City, CA, USA]), a novel formulation of the monobactam aztreonam suitable for aerosol delivery has recently been developed. AZLI is administered as 75 mg three-times daily for 28 days in 'on/off' cycles using the Altera/eFlow electronic nebulizer (PARI Innovative Manufacturers [Midlothian, VA, USA]). In individuals with CF chronically infected with P. aeruginosa, AZLI improved healthcare-associated quality-of-life scores, pulmonary function and weight, prolonged time to requirement of antibacterial therapy for symptoms of pulmonary exacerbation and reduced P. aeruginosa sputum burdens. These outcomes were durable over 18 months of cycled use. AZLI has been demonstrated to be safe and effective, and expands available chronic maintenance therapies in CF.

Ceramide is increased in the lower airway epithelium of people with advanced cystic fibrosis lung disease

RATIONALE

Ceramide accumulates in the airway epithelium of mice deficient in cystic fibrosis transmembrane conductance regulator, resulting in susceptibility to Pseudomonas aeruginosa infection and inflammation.

OBJECTIVES

To investigate quantitatively ceramide levels in the lower airway of people with cystic fibrosis compared with pulmonary hypertension, emphysema, and lung donors.

METHODS

Immunohistochemistry was performed on the lower airway epithelium of explanted lungs (eight cystic fibrosis, emphysema, and pulmonary hypertension, respectively) and eight donor lungs using ceramide, neutrophil elastase, and myeloperoxidase antibodies. High-performance liquid chromatography-mass spectrometry was performed on tissue from five lungs with cystic fibrosis and five with pulmonary hypertension.

MEASUREMENTS AND MAIN RESULTS

Staining for ceramide was significantly increased in the lower airway epithelium of people with cystic fibrosis (median, 14.11%) compared with pulmonary hypertension (3.03%; P = 0.0009); unused lung donors (3.44%; P = 0.0009); and emphysema (5.06%; P = 0.01). Ceramide staining was increased in emphysematous lungs compared with pulmonary hypertension (P = 0.0135) and unused donors (P = 0.0009). The number of neutrophil elastase- and myeloperoxidase-positive cells in the airway was positively correlated with the percentage of epithelium staining for ceramide (P = 0.001). Ceramide staining was significantly increased in lungs colonized with Pseudomonas aeruginosa (10.1%) compared with those not colonized (3.14%; P = 0.0106). Significantly raised levels of ceramides C16:0, C18:0, and C20:0 were detected by mass spectrometry in lungs with cystic fibrosis compared with pulmonary hypertension. Differences in C22:0 were not significant.

CONCLUSIONS

Immunoreactive ceramide is increased in the lower airway epithelium of people with advanced cystic fibrosis. Detected by mass-spectrometry ceramide species C16:0, C18:0, and C20:0 but not C22:0 are increased.