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

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. 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. 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. 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. 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. Not applicable.