Single versus combination intravenous anti-pseudomonal antibiotic therapy for people with cystic fibrosis

Protocol for establishing a core outcome set for evaluation in studies of pulmonary exacerbations in people with cystic fibrosis

INTRODUCTION

Pulmonary exacerbations are associated with increased morbidity and mortality in people with cystic fibrosis (CF). There is no consensus about which outcomes should be evaluated in studies of pulmonary exacerbations or how these outcomes should be measured. Outcomes of importance to people with lived experience of the disease are frequently omitted or inconsistently reported in studies, which limits the value of such studies for informing practice and policy. To better standardise outcome reporting and measurement, we aim to develop a core outcome set for studies of pulmonary exacerbations in people with CF (COS-PEX) and consensus recommendations for measurement of core outcomes.

METHODS AND ANALYSIS

Preliminary work for development of COS-PEX has been reported, including (1) systematic reviews of outcomes and methods for measurement reported in existing studies of pulmonary exacerbations; (2) workshops with people affected by CF within Australia; and (3) a Bayesian knowledge expert elicitation workshop with health professionals to ascertain outcomes of importance. Here we describe a protocol for the additional stages required for COS-PEX development and consensus methods for measurement of core outcomes. These include (1) an international two-round online Delphi survey and (2) consensus workshops to review and endorse the proposed COS-PEX and to agree with methods for measurement.

ETHICS AND DISSEMINATION

National mutual ethics scheme approval has been provided by the Child and Adolescent Health Service Human Research Ethics Committee (RGS 4926). Results will be disseminated via consumer and research networks and peer-reviewed publications. This study is registered with the Core Outcome Measures in Effectiveness Trials database.

The Epidemiology and Pathogenesis and Treatment of Pseudomonas aeruginosa Infections: An Update

Pseudomonas aeruginosa is a Gram-negative bacterial pathogen that is a common cause of nosocomial infections, particularly pneumonia, infection in immunocompromised hosts, and in those with structural lung disease such as cystic fibrosis. Epidemiological studies have identified increasing trends of antimicrobial resistance, including multi-drug resistant (MDR) isolates in recent years. P. aeruginosa has several virulence mechanisms that increase its ability to cause severe infections, such as secreted toxins, quorum sensing and biofilm formation. Management of P. aeruginosa infections focuses on prevention when possible, obtaining cultures, and prompt initiation of antimicrobial therapy, occasionally with combination therapy depending on the clinical scenario to ensure activity against P. aeruginosa. Newer anti-pseudomonal antibiotics are available and are increasingly being used in the management of MDR P. aeruginosa.

Association of Inhaled Antibiotics in Addition to Standard Intravenous Therapy and Outcomes of Pediatric Inpatient Pulmonary Exacerbations

Rationale: Considerable morbidity and disease progression in people with cystic fibrosis (CF) result from pulmonary exacerbations (PExs). PEx guidelines note insufficient evidence to recommend for or against the concomitant use of inhaled and intravenous antibiotics.Objectives: We hypothesize that the addition of inhaled antibiotics for PEx therapy is associated with improvements in lung function and a longer time to next PEx compared with standard intravenous antibiotics alone.Methods: We performed a retrospective cohort study using the CF Foundation Patient Registry-Pediatric Health Information System linked dataset. People with CF were included if they were hospitalized for PEx between 2006 and 2016 and 6 to 21 years of age. Lung function outcomes were assessed by linear mixed effect modeling and generalized estimating equations. The time to next PEx was assessed by Cox proportional hazards regression. To estimate independent causal effects while accounting for indication bias and other confounders, inverse probabilities of treatment weights were calculated based on covariates believed to influence the likelihood of inhaled antibiotic use during PEx treatment.Results: A total of 3,253 children and adolescents contributed 9,040 PEx events for analysis. Inhaled antibiotics were used in 23% of PEx events but were not associated with better pre- to post-PEx percent predicted forced expiratory volume in 1 second responses (mean difference, -1.11%; 95% confidence interval [CI], -1.83 to -0.38; P = 0.003), higher odds of returning to lung function baseline (odds ratio, 0.94; 95% CI, 0.82 to 1.07; P = 0.34), or longer time to next PEx (hazard ratio, 1.05; 95% CI, 0.99 to 1.12; P = 0.098).Conclusions: The addition of inhaled antibiotics to standard intravenous antibiotic PEx treatment was not associated with improved lung function outcomes or a longer time to next PEx.

Polymicrobial Interactions in the Cystic Fibrosis Airway Microbiome Impact the Antimicrobial Susceptibility of Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the most dominant pathogens in cystic fibrosis (CF) airway disease and contributes to significant inflammation, airway damage, and poorer disease outcomes. The CF airway is now known to be host to a complex community of microorganisms, and polymicrobial interactions have been shown to play an important role in shaping P. aeruginosa pathogenicity and resistance. P. aeruginosa can cause chronic infections that once established are almost impossible to eradicate with antibiotics. CF patients that develop chronic P. aeruginosa infection have poorer lung function, higher morbidity, and a reduced life expectancy. P. aeruginosa adapts to the CF airway and quickly develops resistance to several antibiotics. A perplexing phenomenon is the disparity between in vitro antimicrobial sensitivity testing and clinical response. Considering the CF airway is host to a diverse community of microorganisms or 'microbiome' and that these microorganisms are known to interact, the antimicrobial resistance and progression of P. aeruginosa infection is likely influenced by these microbial relationships. This review combines the literature to date on interactions between P. aeruginosa and other airway microorganisms and the influence of these interactions on P. aeruginosa tolerance to antimicrobials.

Pulmonary Exacerbations in Adults With Cystic Fibrosis: A Grown-up Issue in a Changing Cystic Fibrosis Landscape

Pulmonary exacerbations (PExs) are significant life events in people with cystic fibrosis (CF), associated with declining lung function, reduced quality of life, hospitalizations, and decreased survival. The adult CF population is increasing worldwide, with many patients surviving prolonged periods with severe multimorbid disease. In many countries, the number of adults with CF exceeds the number of children, and PExs are particularly burdensome for adults as they tend to require longer courses and more IV treatment than children. The approach to managing PExs is multifactorial and needs to evolve to reflect this changing adult population. This review discusses PEx definitions, precipitants, treatments, and the wider implications to health-care resources. It reviews current management strategies, their relevance in particular to adults with CF, and highlights some of the gaps in our knowledge. A number of studies are underway to try to answer some of the unmet needs, such as the optimal length of treatment and the use of nonantimicrobial agents alongside antibiotics. An overview of these issues is provided, concluding that with the changing landscape of adult CF care, the definitions and management of PExs may need to evolve to enable continued improvements in outcomes across the age spectrum of CF.

Outcomes and endpoints reported in studies of pulmonary exacerbations in people with cystic fibrosis: A systematic review

BACKGROUND

There is no consensus about which outcomes should be evaluated in studies of pulmonary exacerbations in people with cystic fibrosis (CF). Outcomes used for evaluation should be meaningful; that is, they should capture how people feel, function or survive and be acknowledged as important to people with CF, or should be reliable surrogates of those outcomes. We aimed to summarise the outcomes and corresponding endpoints which have been reported in studies of pulmonary exacerbations, and to identify those which are most likely to be meaningful.

METHODS

A PROSPERO registered systematic review (CRD42020151785) was conducted in Medline, Embase and Cochrane from inception until July 2020. Registered trials were also included.

RESULTS

144 studies met the inclusion criteria. A wide range of outcomes and corresponding endpoints were reported. Death, QoL and many patient-reported outcomes are likely to be meaningful as they directly capture how people feel, function or survive. Forced expiratory volume in 1-second [FEV₁] is a validated surrogate of risk of death and reduced QoL. The extent of structural lung disease has also been correlated with lung function, pulmonary exacerbations and risk of death. Since no evidence of a correlation between airway microbiology or biomarkers with clinically meaningful outcomes was found, the value of these as surrogates was unclear.

CONCLUSIONS

Death, QoL, patient-reported outcomes, FEV₁, and structural lung changes were identified as outcomes that are most likely to be meaningful. Development of a core outcome set in collaboration with stakeholders including people with CF is recommended.

Pseudomonas aeruginosa antimicrobial susceptibility test (AST) results and pulmonary exacerbation treatment responses in cystic fibrosis

Background Antimicrobial susceptibility testing (AST) of bacterial isolates is a time- and resource-intensive procedure recommended by cystic fibrosis (CF) treatment guidelines for antimicrobial selection for pulmonary exacerbation (PEx) treatment. Methods We studied relationships between Pseudomonas aeruginosa (Pa) isolate AST results, antipseudomonal PEx treatments, and treatment responses as change in weight and percent predicted forced expiratory volume in 1 s (ppFEV₁) as well as future antimicrobial treatment hazard for PEx occurring at a CF care center from 1999 through 2018. Treatments were categorized by "Pa coverage" as complete (all Pa isolates susceptible by AST to at least one administered agent), none (no isolates susceptible), incomplete (some, but not all isolates susceptible), and indeterminant (administered antipseudomonals not evaluated by AST). Weight and ppFEV₁ responses were compared across Pa coverage categories using unadjusted and adjusted general estimating equations; hazard of future treatment was assessed by Cox and logistic regression. Results Among 3820 antimicrobial PEx treatment events in 413 patients with Pa, 62.6% (2390) had complete Pa coverage; 8.9% (340), 2.4% (99), and 26.2% (1000), had no, incomplete, and indeterminant Pa coverage, respectively. Mean baseline to follow-up weight change was +0.74 kg [95% CI 0.63, 0.86]; ppFEV₁ change was +1.60 [1.29, 1.90]. Pa coverage category was not associated with significant differences in weight or ppFEV₁ change or with future antimicrobial treatment hazard. Conclusions We did not observe superior responses for AST-defined complete Pa coverage treatments versus lesser coverage treatments, suggesting that AST may be of little utility in choosing antimicrobials for CF PEx treatment.

Combined Efficacy of an Antimicrobial Cationic Peptide Polymer with Conventional Antibiotics to Combat Multidrug-Resistant Pathogens

Antibiotic-resistant infections are predicted to kill 10 million people worldwide per year by 2050 and to cost the global economy 100 trillion USD. Novel approaches and alternatives to conventional antibiotics are urgently required to combat antimicrobial resistance. We have synthesized a chitosan-based oligolysine antimicrobial peptide, CSM5-K5 (where CSM denotes chitosan monomer repeat units and K denotes lysine amino acid repeat units), that targets multidrug-resistant (MDR) bacterial species. Here, we show that CSM5-K5 exhibits rapid bactericidal activity against methicillin-resistant Staphylococcus aureus (MRSA), MDR Escherichia coli, and vancomycin-resistant Enterococcus faecalis (VRE). Combinatorial therapy of CSM5-K5 with antibiotics to which each organism is otherwise resistant restores sensitivity to the conventional antibiotic. CSM5-K5 alone significantly reduced preformed bacterial biofilm by 2-4 orders of magnitude and, in combination with conventional antibiotics, reduced preformed biofilm by more than 2-3 orders of magnitude at subinhibitory concentrations. Moreover, using a mouse excisional wound infection model, CSM5-K5 treatment reduced bacterial burdens by 1-3 orders of magnitude and acted synergistically with oxacillin, vancomycin, and streptomycin to clear MRSA, VRE, and MDR E. coli, respectively. Importantly, little to no resistance against CSM5-K5 arose for any of the three MDR bacteria during 15 days of serial passage. Furthermore, low level resistance to CSM5-K5 that did arise for MRSA conferred increased susceptibility (collateral sensitivity) to the β-lactam antibiotic oxacillin. This work demonstrates the feasibility and benefits of using this synthetic cationic peptide as an alternative to, or in combination with, traditional antibiotics to treat infections caused by MDR bacteria.

Synergy between Synthetic Antimicrobial Polymer and Antibiotics: A Promising Platform To Combat Multidrug-Resistant Bacteria

The failure of many antibiotics in the treatment of chronic infections caused by multidrug-resistant (MDR) bacteria necessitates the development of effective strategies to combat this global healthcare issue. Here, we report an antimicrobial platform based on the synergistic action between commercially available antibiotics and a potent synthetic antimicrobial polymer that consists of three key functionalities: low-fouling oligoethylene glycol, hydrophobic ethylhexyl, and cationic primary amine groups. Checkerboard assays with Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli demonstrated synergy between our synthetic antimicrobial polymer and two antibiotics, doxycycline and colistin. Coadministration of these compounds significantly improved the bacteriostatic efficacy especially against MDR P. aeruginosa strains PA32 and PA37, where the minimal inhibitory concentrations (MICs) of polymer and antibiotics were reduced by at least 4-fold. A synergistic killing activity was observed when the antimicrobial polymer was used in combination with doxycycline, killing >99.999% of planktonic and biofilm P. aeruginosa PAO1 upon a 20 min treatment at a polymer concentration of 128 μg mL^-1 (4.6 μM) and doxycycline concentration of 64 μg mL^-1 (133.1 μM). In addition, this synergistic combination reduced the rate of resistance development in P. aeruginosa compared to individual compounds and was also capable of reviving susceptibility to treatment in the resistant strains.

Cystic Fibrosis Airway Microbiome: Overturning the Old, Opening the Way for the New

The genetic disease cystic fibrosis (CF) is associated with chronic airway infections that are a proximal cause of death in many patients with this affliction. Classic microbiology studies focusing on canonical pathogens resulted in the development of a common set of views regarding the nature of the airway infections associated with this disease, and these ideas have influenced everything from the way infections are treated to how clinical trials for new CF-targeted antibiotics are designed and the focus of CF-related research topics. Recent culture-independent studies have prompted us to rethink, and in some cases discard, some of these long-held views. In this piece, I argue that an updated view of the complicated chronic infections associated with CF, thanks in large part to culture-independent studies of sputum and bronchoalveolar lavage fluid samples, should be leveraged to develop new strategies to treat these recalcitrant infections.

Relevance of multidrug-resistant Pseudomonas aeruginosa infections in cystic fibrosis

Multidrug-resistant (MDR) Pseudomonas aeruginosa is an important issue for physicians who take care of patients with cystic fibrosis (CF). Here, we review the latest research on how P. aeruginosa infection causes lung function to decline and how several factors contribute to the emergence of antibiotic resistance in P. aeruginosa strains and influence the course of the infection course. However, many aspects of the practical management of patients with CF infected with MDR P. aeruginosa are still to be established. Less is known about the exact role of susceptibility testing in clinical strategies for dealing with resistant infections, and there is an urgent need to find a tool to assist in choosing the best therapeutic strategy for MDR P. aeruginosa infection. One current perception is that the selection of antibiotic therapy according to antibiogram results is an important component of the decision-making process, but other patient factors, such as previous infection history and antibiotic courses, also need to be evaluated. On the basis of the known issues and the best current data on respiratory infections caused by MDR P. aeruginosa, this review provides practical suggestions to optimize the diagnostic and therapeutic management of patients with CF who are infected with these pathogens.