Abstract: Objective To explore the drug resistance of Pseudomonas aeruginosa in patients with severe respiratory disease and environment, and to conduct molecular epidemiological investigations on it. Methods The strains of Pseudomonas aeruginosa isolated from patients with severe respiratory disease and the environment in a hospital in Xi'an from 2020 to 2022 were collected for drug sensitivity test and drug resistance gene detection, and the homology of Pseudomonas aeruginosa strains was analyzed by using multiple site sequence typing （MLST） and pulsed field gel electrophoresis （PFGE）. Results A total of 994 strains of Pseudomonas aeruginosa were collected, of which 668 strains were from patients, accounting for 67.20%, and 326 strains （32.80%） were from environmental samples. The drug sensitivity test showed that the resistance rates to amitriptyline and piperacillin were the highest, exceeding 30%; Next were imipenem （28.37%） and meropenem （29.18%）, with resistance rates to piperacillin/tazobactam, ciprofloxacin, levofloxacin, ceftazidime, cefepime, and cefoperazone/sulbactam all ranging from 20% to 30%. The resistance rates to aminoglycoside antibiotics and lipopeptides were below 20%, with polymyxin B （1.51%） being the lowest. The sequencing results of resistance genes showed that the positive rate of OprD2 gene was the highest, at 33.60%; Next were aminoglycoside modifying enzymes aac （6’）-Ib （28.97%） and ant （3"）-I （27.16%）, as well as the carbapenem enzyme gene bla_IMP （22.64%） and ESBLs gene bla_TEM （19.52%）. Thirty‐one STs types were classified by MLST, mainly ST235 （38.53%）, ST244 （31.09%）, and ST298 （12.68%）. The PFGE typing result identified a total of 16 subtypes from A to Q, with type A （34.21%） and type C （21.33%） being the main subtypes. Conclusions Drug resistance of Pseudomonas aeruginosa strains is common in patients with severe respiratory disease, with ST235 and ST244 being the main prevalent clones in the local area. Targeted strengthening of hospital infection monitoring for patients with severe respiratory disease and cleaning of the intensive care unit is beneficial for controlling the spread and prevalence of Pseudomonas aeruginosa.

Key words: Severe respiratory disease, Pseudomonas aeruginosa, Drug resistance, Molecular epidemiology