Case report: Genotype analysis of a patient with bronchiectasis infected by a rare strain of Pseudomonas aeruginosa

Background Pseudomonas aeruginosa (PA) is the most common pathogen in patients with bronchiectasis. Its structural changes and recurrent infections pose significant challenges and difficulties for clinical treatment. Despite extensive study, the resistance mechanisms remain elusive. Case presentation We report a patient with bronchiectasis who suffered from dyspnea and was hospitalized for years, but the pathogen was never detected on routine sputum cultures and his symptoms could not be controlled. Our team collected bronchoalveolar lavage fluid (BALF) and identified the pathogen as PA through nanopore sequencing. The BALF was incubated on 5% CO ₂ blood agar for 48 hours, producing only sparse colonies with slow growth. Whole genome analysis of the bacterium identified the genotype as ST270, which is rarely reported both domestically and internationally. Non-functional mutations in the PilI and ChpA genes of this strain caused slow growth, making cultivation difficult. Additionally, the overexpression of the AmpD and LysR genes, along with mutations in the regulatory genes AmiD , DacC , and DacB , resulted in multi-drug resistance in the strain, complicating treatment. Conclusion This case report, through whole-genome sequencing, comprehensively elucidates the resistance mechanisms of Pseudomonas aeruginosa and discovers a rare genotype, providing a deep and innovative approach to the study.