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As more patients with cystic fibrosis (CF) are living into adulthood, patients may need to disclose their CF status to others, such as in romantic or professional settings. Patients who choose not to disclose their CF status may be limited in their closeness with others, which may negatively affect their psychological functioning and health-related quality of life. Few studies, however, have examined disclosure in CF, and currently no validated measures of CF disclosure exist. The purpose of this study was to explore CF disclosure in adults and validate a new assessment of CF disclosure, the Cystic Fibrosis Disclosure Scale (CFDS). Results were consistent with prior research in disclosure in CF, with participants disclosing most often to close others and less often at school or in the workplace. Disclosure to close and casual friends was consistently associated with better psychosocial functioning. Factor analyses determined the CFDS was valid and that all questions should be retained. The Count Group subscale emerged as the “best” subscale grouping and coding method. This study contributed to the literature by serving as the first validation study of a questionnaire of disclosure in CF. Additionally, as disclosure in CF is a new emerging area, this study added information to the sparse literature on this issue. The CFDS as it exists now gathers important research and clinical information from adults with CF, and should be examined further with a larger sample size and more descriptive information.

Mycobacterium abscessus is an emerging pathogen with infections increasing worldwide, especially among Cystic Fibrosis (CF) patients. During my PhD, I studied key aspects of the biology of M. abscessus spp.; particularly, I studied host-pathogen interactions, antimicrobial resistance mechanisms, and genetic determinants of virulence. First, I performed phenotypic characterization of M. abscessus spp. clinical isolates obtained from CF patients classified according to subspecies and clustering. I found clustered isolates, representing probable transmission events, were phenotypically distinct from sporadic isolates and showed adaptation phenotypes associated with chronic lung infection, such as enhanced intracellular survival, increased antibiotic resistance, and metabolic adaptations to the host environment. Second, I assessed the role of an inserted element containing an active methyltransferase in M. a. massiliense. Infection experiments with an isolate containing the inserted element (BIR1049wt) and a knockout strain (BIR1049Δ1809078_1815649) showed decreased survival of BIR1049Δ1809078_1815649 within macrophages. RNAseq analysis showed a distinct gene expression pattern between both isolates, with a number of mycobacterial virulence factors upregulated in BIR1049wt. Third, I studied heritable non-mutational antibiotic resistance mechanisms in M. abscessus to linezolid and clofazimine. For both antibiotics, I found clonal isolates of M. abscessus spp. with varying susceptibilities and different gene expression patterns, suggesting transcriptional regulation of antibiotic resistance. Mutation- mediated resistance to clofazimine was also found due to mutations in two transcriptional regulators predicted to regulate efflux pumps. Last, I evaluated the potential of repurposing a kinase inhibitor (compound H) in clinical trials for the treatment of cancer and CF, to treat M. abscessus infection. I found compound H enhanced killing of intracellular M. abscessus in macrophages through stimulation of autophagy and lysosomal function. I further studied over 60 chemical analogues of compound H in order to find a more active and specific compound for M. abscessus infection.

Aspergillus fumigatus is increasingly recognised as a cystic fibrosis (CF) pathogen with reported infection rates up to 50% and associated with increased hospitalisations and lung deterioration. Research investigating immune responses of CF phagocytes against A. fumigatus has been scarce and the role of the cystic fibrosis transmembrane conductance regulator (CFTR) protein in anti-Aspergillus immune responses is not known. The studies in this thesis aimed to explore innate immune responses by CF phagocytes against A. fumigatus. Peripheral blood mononuclear cells (PBMC), monocytes (MNC) and polymorphonuclear cells (PMN) were isolated from blood samples of CF patients with at least one copy of the F508del mutation. CF phagocytes efficiently cleared A. fumigatus similar to healthy controls. Microtubuleassociated proteins 1A/1B light chain 3B (LC3) expression was found to be attenuated in CF PMN and MNC, indicating a disbalance in the autophagy or LC3-associated phagocytosis pathway. Regarding inflammatory responses, it was found that upon phagocytosis a resting A. fumigatus conidia, CF phagocytes produce up to 4-fold more reactive oxygen species (ROS) compared to controls. The excessive ROS was then shown not to be necessary for adequate killing, suggesting the increased ROS to be redundant in the antifungal response. Patient metrics obtained from the clinic showed that the excessive ROS production correlated to exacerbations and lung function. Liquid chromatography-mass spectrometry (LC-MS) analysis revealed that CF PMN only express 20-25% of the 4 haemoglobin subunits compared to healthy controls. Combining the LC-MS data suggests that CF PMN are under hypoxic stress. In conclusion, the effective clearance of A. fumigatus by CF phagocytes comes at the cost of an excessive respiratory burst which correlates to disease severity. Our data indicate that CF PMN are under hypoxic stress while circulating in the blood stream, which is likely to contribute to the hyperinflammatory phenotype observed upon interaction with A. fumigatus.