Antimicrobial Resistance, Molecular Epidemiology, and Virulence Profiles of Hypervirulent Carbapenem-Resistant Klebsiella pneumoniae Isolates from a Tertiary Hospital in Zunyi, Southwest China, 2021-2023.

BACKGROUND: To systematically analyze the drug resistance phenotype, virulence characteristics, and molecular epidemiological characteristics of hypervirulent carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) in Zunyi area, and to provide experimental and epidemiological evidence for clinical accurate diagnosis and treatment, rational selection of antibiotics, and prevention and control of nosocomial infection of hv-CRKP in the region. METHODS: A total of 91 hv-CRKP strains were collected from the First People's Hospital of Zunyi from 2021 to 2023. Drug susceptibility test was performed for commonly used antibiotics in clinic. Molecular typing included PCR detection of carbapenemase gene, multilocus sequence typing (MLST), membrane porin (OmpK) deletion analysis, and capsule serotyping. The virulence phenotype of hv-CRKP was comprehensively evaluated by biofilm formation, serum resistance, and Galleria mellonella larval infection tests. RESULTS: hv-CRKP strains were highly resistant to commonly used antibiotics, but the resistance rate to tigecycline was relatively low, only 3.3%. The clones carrying virulence genes iucA, iroB and rmpA2 were the dominant clones, accounting for 83.52%. Most of them carried Carbapenem resistance genes blaKPC-2, with a positive rate of 95.60%. The predominant sequence type of hv-CRKP isolates was ST11, accounting for 87.90%. The expression of OmpK35 and OmpK37 was characterized by full expression of Ompk35 and Ompk37, while the expression rate of OmpK36 was low (6.59%). 79.12% of the strains had the ability of biofilm formation. The predominant capsular serotype was KL64, accounting for 87.90%. Its serum bactericidal tolerance was only 12.08%. ST65 was the most virulent strain of KL64 strain, and KL114 was the most virulent strain of ST11 strain. CONCLUSION: The main hv-CRKP strains in this region carry the iucA, iroB and rmpA2 virulence genes simultaneously, and the dominant clone type is ST11-KL64. The production of carbapenemase mainly involves blaKPC-2. The rate of loss of OmpK36 outer membrane pore protein and the rate of biofilm formation are relatively high. This study can provide important references for the diagnosis and treatment of hv-CRKP infections.