Pulmonary bacteriophage and cystic fibrosis airway mucus: friends or foes?

For those born with cystic fibrosis (CF), hyper-concentrated mucus with a dysfunctional structure significantly impacts CF airways, providing a perfect environment for bacterial colonization and subsequent chronic infection. Early treatment with antibiotics limits the prevalence of bacterial pathogens but permanently alters the CF airway microenvironment, resulting in antibiotic resistance and other long-term consequences. With little investment into new traditional antibiotics, safe and effective alternative therapeutic options are urgently needed. One gathering significant traction is bacteriophage (phage) therapy. However, little is known about which phages are effective for respiratory infections, the dynamics involved between phage(s) and the host airway, and associated by-products, including mucus. Work utilizing gut cell models suggest that phages adhere to mucus components, reducing microbial colonization and providing non-host-derived immune protection. Thus, phages retained in the CF mucus layer result from the positive selection that enables them to remain in the mucus layer. Phages bind weakly to mucus components, slowing down the diffusion motion and increasing their chance of encountering bacterial species for subsequent infection. Adherence of phage to mucus could also facilitate phage enrichment and persistence within the microenvironment, resulting in a potent phage phenotype or vice versa. However, how the CF microenvironment responds to phage and impacts phage functionality remains unknown. This review discusses CF associated lung diseases, the impact of CF mucus, and chronic bacterial infection. It then discusses the therapeutic potential of phages, their dynamic relationship with mucus and whether this may enhance or hinder airway bacterial infections in CF.

The effect of inhaled hypertonic saline on lung structure in children aged 3-6 years with cystic fibrosis (SHIP-CT): a multicentre, randomised, double-blind, controlled trial.

BACKGROUND: In the Saline Hypertonic in Preschoolers (SHIP) study, inhaled 7% hypertonic saline improved the lung clearance index in children aged 3-6 years with cystic fibrosis, but it remained unclear whether improvement is also seen in structural lung disease. We aimed to assess the effect of inhaled hypertonic saline on chest CT imaging in children aged 3-6 years with cystic fibrosis. METHODS: Children with cystic fibrosis were enrolled in this multicentre, randomised, double-blind, controlled study at 23 cystic fibrosis centres in Spain, Denmark, the Netherlands, Italy, France, Belgium, the USA, Canada, and Australia. Eligible participants were children aged 3-6 years who were able to cooperate with chest CT imaging and comply with daily nebuliser treatment. Participants were randomly assigned 1:1 to receive inhaled 2 puffs of 100 µg salbutamol followed by 4mL of either 7% hypertonic saline or 0·9% isotonic saline twice per day for 48 weeks. Randomisation was stratified by age in North America and Australia, and by age and country in Europe. Chest CTs were obtained at baseline and 48 weeks and scored using the Perth-Rotterdam Annotated Grid Morphometric Analysis for Cystic Fibrosis (PRAGMA-CF) method. The primary outcome was the difference between groups in the percentage of total lung volume occupied by abnormal airways (PRAGMA-CF %Disease) measured by chest CT at 48 weeks. Analysis was by intention-to-treat. This study is registered with Clinicaltrials.gov, NCT02950883. FINDINGS: Between May 24, 2016, and Dec 18, 2019, 134 children were assessed for inclusion. 18 patients were excluded (nine had incomplete or unsuccessful chest CT at enrolment visit, two could not comply with CT training, two had acute respiratory infection, two withdrew consent, two for reasons unknown, and one was already on hypertonic saline). 116 participants were enrolled and randomly assigned to hypertonic saline (n=56) or isotonic saline (n=60). 12 patients dropped out of the study (seven in the hypertonic saline group and five in the isotonic saline group). Mean PRAGMA-CF %Disease at 48 weeks was 0·88% (95% CI 0·60-1·16) in the hypertonic saline group and 1·55% (1·25-1·84) in the isotonic saline group (mean difference 0·67%, 95% CI 0·26-1·08; p=0·0092) based on a linear regression model adjusted for baseline %Disease values and baseline age. Most adverse events in both groups were rated as mild, and the most common adverse event in both groups was cough. INTERPRETATION: Inhaled hypertonic saline for 48 weeks had a positive effect on structural lung changes in children aged 3-6 years with cystic fibrosis relative to isotonic saline. This is the first demonstration of an intervention that alters structural lung disease in children aged 3-6 years with cystic fibrosis. FUNDING: Cystic Fibrosis Foundation.

Development and validation of a miniaturized bacteriophage host range screening assay against antibiotic resistant Pseudomonas aeruginosa.

Antimicrobial resistance is a current global health crisis, and the increasing emergence of multidrug resistant infections has led to the resurgent interest in bacteriophages as an alternative treatment. Prior to clinical application, phage suitability is assessed, via susceptibility testing and breadth of host range to bacteriophage, however, these are both large-scale manual processes and labor-intensive. The aim of the study was to establish and validate a scaled down methodology for high-throughput screening to reduce procedural footprint. In this paper, we describe a scaled-down adapted methodology that can successfully screen bacteriophages, isolated and purified from wastewater samples. Furthermore, we describe a miniaturized host range assay against clinical Pseudomonas aeruginosa isolates using a spot test (2 µL/ drop) that was found to be both sensitive (94.6%) and specific (94.7%). It also demonstrated a positive predictive value (PPV) of 86.4% and negative predictive value (NPV) of 98%. The breadth of host range of bacteriophages that exhibited lytic activity on P. aeruginosa isolates was corroborated using the scaled down assay. The high correlation achieved in this study confirms miniaturization as the first step in future automation that could test phage diversity and efficacy as antimicrobials.