Impact of airway Exophiala spp. on children with cystic fibrosis

Metagenomics Applied to the Respiratory Mycobiome in Cystic Fibrosis

Cystic fibrosis (CF) is a genetic disorder characterized by chronic microbial colonization and inflammation of the respiratory tract (RT), leading to pulmonary exacerbation (PEx) and lung damage. Although the lung bacterial microbiota has been extensively studied, the mycobiome remains understudied. However, its importance as a contributor to CF pathophysiology has been highlighted. The objective of this review is to provide an overview of the current state of knowledge regarding the mycobiome, as described through NGS-based studies, in patients with CF (pwCF).Several studies have demonstrated that the mycobiome in CF lungs is a dynamic entity, exhibiting a lower diversity and abundance than the bacterial microbiome. Nevertheless, the progression of lung damage is associated with a decrease in fungal and bacterial diversity. The core mycobiome of the RT in pwCFs is mainly composed of yeasts (Candida spp., Malassezia spp.) and molds with lower abundance. Some fungi (Aspergillus, Scedosporium/Pseudallescheria) have been demonstrated to play a role in PEx, while the involvement of others (Candida, Pneumocystis) remains uncertain. The "climax attack" ecological model has been proposed to explain the complexity and interplay of microbial populations in the RT, leading to PEx and lung damage. NGS-based studies also enable the detection of intra- and interkingdom correlations between fungi and bacteria. Further studies are required to ascertain the biological and pathophysiological relevance of these correlations. Finally, with the recent advent of CFTR modulators, our understanding of the pulmonary microbiome and mycobiome in pwCFs is about to change.

Therapeutic drug monitoring-guided dosing for pediatric cystic fibrosis patients: recent advances and future outlooks

INTRODUCTION

Medicine use in children with cystic fibrosis (CF) is complicated by inconsistent pharmacokinetics at variance with the general population, a lack of research into this and its effects on clinical outcomes. In the absence of established dose regimens, therapeutic drug monitoring (TDM) is a clinically relevant tool to optimize drug exposure and maximize therapeutic effect by the bedside. In clinical practice though, use of this is variable and limited by a lack of expert recommendations.

AREAS COVERED

We aimed to review the use of TDM in children with CF to summarize recent developments, current recommendations, and opportunities for future directions. We searched PubMed for relevant publications using the broad search terms "cystic fibrosis" in combination with the specific terms "therapeutic drug monitoring (TDM)" and "children." Further searches were undertaken using the name of identified drugs combined with the term "TDM."

EXPERT OPINION

Further research into the use of Bayesian forecasting and the relationship between exposure and response is required to personalize dosing, with the opportunity for the development of expert recommendations in children with CF. Use of noninvasive methods of TDM has the potential to improve accessibility to TDM in this cohort.

Isolation of Exophiala dermatitidis is not associated with worse clinical outcomes during acute pulmonary exacerbations in cystic fibrosis

Introduction. The black yeast Exophiala dermatitidis has been isolated in respiratory samples from people with cystic fibrosis (CF). However, adequate detection may require longer incubation periods than the current UK national standard for CF respiratory samples. Furthermore, it is unclear whether isolation of E. dermatitidis is associated with poorer clinical outcomes in CF.

Hypothesis/gap statement. E. dermatitidis does not cause clinically significant lung disease in CF adults.

Aim. To evaluate differences in clinical outcomes over a 12 month period and during acute pulmonary exacerbations between CF adults with and without untreated E. dermatitidis.

Methodology. Incubation times for respiratory samples on Sabouraud dextrose agar with chloramphenicol (SABC) plates at a large regional adult CF centre were extended from 2 to 7 days over a 1 month period. The number of patients from whom E. dermatitidis was isolated, and the length of incubation time prior to isolation, were recorded. Outcomes of treatment of exacerbations with intravenous antibiotics but in the absence of concomitant antifungal therapy were compared between those with and without E. dermatitidis, as were changes in lung function and body mass index (BMI) over a 12 month period.

Results. Extended incubation unmasked the presence of E. dermatitidis in 22 of 132 patients; all isolations occurred after >48 h of incubation. Patients who isolated E. dermatitidis had lower rates of Pseudomonas aeruginosa isolation (P=0.02) and higher rates of non-tuberculous mycobacteria isolation (P=0.03), and were more likely to be prescribed a long-term antifungal medication (P=0.03), but had no differences in age, sex, baseline lung function or body mass index (BMI). There were no differences in response to treatment of acute exacerbations between patients with and without E. dermatitidis, or in change in forced expiratory volume in 1 s (FEV1), BMI and number of exacerbations over 12 months of follow-up.

Conclusion. E. dermatitidis is not associated with worse clinical outcomes in CF. Given potential side effects and drug interactions, routine targeting of E. dermatitidis with antifungals during acute exacerbations is not advised.

The Presence of Exophiala dermatitidis in the Respiratory Tract of Cystic Fibrosis Patients Accelerates Lung Function Decline: A Retrospective Review of Lung Function

Exophiala dermatitidis is increasingly isolated from cystic fibrosis (CF) respiratory samples. The decision to treat is hampered by limited evidence demonstrating the clinical significance of isolating E. dermatitidis. The objective was to assess the impact of E. dermatitidis isolation on the lung function of CF patients. The rate of lung function decline in the local CF population was calculated using historic lung function data. A control population who had never had E. dermatitidis cultured from the respiratory tract was compared with the E. dermatitidis group, calculating their rate of lung function decline before and after the first isolation of the organism. A total of 1840 lung function measurements were reviewed between the 31 E. dermatitidis group patients and 62 control patients. Their demographics were similar. The control group declined at a rate of −0.824 FEV1%/year. The rate of decline in the E. dermatitidis group prior to infection was −0.337 FEV1%/year (p = 0.2). However, post infection with E. dermatitidis, there was a significant increase in the rate of decline in lung function (−1.824 FEV1%/year, p < 0.01). The results suggest E. dermatitidis has a temporal relationship with accelerated rate of lung function decline. It is not clear if this is a cause or effect, but this accelerated rate of decline indicates a need for further investigation.