Drug resistance mechanisms and molecular epidemiology of carbapenem-resistant Klebsiella pneumoniae in pulmonary infections.

BACKGROUND: As a highly drug-resistant nosocomial pathogen, Carbapenem-resistant Klebsiella pneumoniae (CRKP) often causes pulmonary infections with high mortality rates, and deciphering its molecular characteristics and drug resistance mechanisms is crucial for rational clinical drug use. OBJECTIVE: This study aimed to investigate the drug resistance mechanisms and molecular epidemiological characteristics of pulmonary infections caused by CRKP. The findings intend to provide a scientific basis for optimizing antibiotic use and developing effective clinical prevention and control measures. METHODS: Non-repetitive CRKP strains isolated from bronchoalveolar lavage fluid and qualified sputum samples of hospitalized patients at a Class A tertiary hospital in Yunnan Province from April 2020 to June 2024 were collected. The VITEK 2 Compact automatic bacterial identification system, along with the Kirby-Bauer disk diffusion method and broth microdilution method, were employed to conduct antimicrobial susceptibility testing and assess resistance phenotypes. Additionally, whole-genome sequencing (WGS) technology was employed to analyze resistance genes, virulence genes, and multi-locus sequence typing (MLST), and a phylogenetic tree was constructed. RESULTS: A total of 70 non-repetitive CRKP isolates were collected. The strains exhibited high resistance to most antimicrobial agents but remained sensitive to tigecycline, polymyxin B, and ceftazidime/avibactam. Various antibiotic resistance genes were identified, with blaKPC−2 (62.9%) being the predominant carbapenemase gene, followed by blaOXA−232 (22.9%). High detection rates were observed for virulence genes, including type I pili (fimCDFGHI), type III pili (mrkABCDFHJ), and iron-uptake system genes (iroN, iutA, fep, ent, fes). Six sequence types were identified, with ST11 (61.4%) being the most prevalent. CONCLUSION: CRKP strains isolated from pulmonary infections displayed extensive multidrug resistance, primarily attributed to the ST11 lineage and blaKPC−2 as the main carbapenemase gene. The frequent detection of multiple key virulence factors underscores the importance of precise antibacterial treatment and vigilant molecular epidemiological surveillance. CLINICAL TRIAL NUMBER: Not applicable.