Resistance of Pseudomonas aeruginosa to Antibiotics During Long-Term Persistence in Patients with Cystic Fibrosis

<i>Pseudomonas aeruginosa</i> is one of the leading causes of nosocomial respiratory tract infections, significantly affecting morbidity and mortality. It can persist in the lungs of patients with cystic fibrosis (CF) for extended periods because of its adaptive capacity. The main aim of this study was to determine the phenotypic and genotypic resistance to antibiotics of clinical isolates of <i>P. aeruginosa</i> that persist in patients with CF receiving long-term antimicrobial therapy. The study included nine strains of <i>P. aeruginosa</i> isolated from the sputum of patients with CF admitted to the hospital. Susceptibility to antibiotics was determined using the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. Whole-genome sequencing was performed for phylogeny, sequence typing, and to identify antibiotic-resistant genes. The study showed that during long-term persistence in the lungs of patients receiving antibacterial therapy, the restoration of susceptibility to antibiotics occurred in some cases. Multilocus sequence typing and phylogeny revealed six sequence types. Functional annotation identified 72 genes responsible for resistance to antibacterial and chemical substances, with either chromosomal or plasmid localisation.