Introduction: Pseudomonas aeruginosa is a multi-drug resistant, opportunistic pathogen causing recalcitrant pulmonary infections in people with cystic fibrosis (pwCF). In the past decade there has been considerable improvements in CF precision medicine including the development of CF transmembrane conductance regulator (CFTR) modulators which correct the underlying defective chloride channel driving disease. These novel modulators have drastically improved patient outcomes however various studies have revealed that despite an initial drop in P. aeruginosa sputum load, infection is sustained, and bacterial numbers can return after the first year of treatment in chronically colonised adults [1, 2]. Here, we aim to investigate how P. aeruginosa infections in CF may change and adapt in the face of the altered lung environment post modulation.
Methods and Results: A total of 105 P. aeruginosa isolates were collected at baseline and up to 18 months post therapy with the latest CFTR modulator combinations, Trikafta (n = 10) and Symdeko (n = 1) from pwCF. Whole genome sequencing and comparisons of multi-locus sequence types and average nucleotide identity revealed that patients retain the same clonal isolates after treatment, rather than being displaced with alternative strains. Additionally, the classically chronic alginate-producing mucoid phenotype and lack of O-antigen expression is sustained post therapy. No apparent changes in antibiotic susceptibility were observed through disc diffusion methods.
Conclusion: These preliminary results reveal that chronic P. aeruginosa phenotypes remain post CFTR modulator initiation likely due to irreversible lung damage continuing to create a niche for these microbes. Further genomics analysis including presence of single nucleotide polymorphisms, changes in metabolic pathways and phenotypic microarrays are underway to determine whether these clonal strains have mutated and adapted to the modulated CF lung.