Bailong Hou,1,* Ying Zhou,2,* Wei Wang,1 Weifeng Shen,1 Qinlong Yu,1 Minjie Mao,1 Siheng Wang,1 Wenxiu Ai,3 Fangyou Yu,2,3 Pingyang Shao1 

1Department of Clinical Laboratory Medicine, The First Hospital of Jiaxing, The Affiliated Hospital of Jiaxing University, Jiaxing, 314000, People’s Republic of China; 2Department of Clinical Laboratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, 200000, People’s Republic of China; 3Department of Clinical Laboratory, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325000, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Pingyang Shao, Department of Clinical Laboratory Medicine, The First Hospital of Jiaxing, The Affiliated Hospital of Jiaxing University, Jiaxing, 314000, People’s Republic of China, Email spy202001@163.com Fangyou Yu, Department of Clinical Laboratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, 200000, People’s Republic of China, Email wzjxyfy@163.com

Introduction: This study aimed to investigate the emergence and characteristics of carbapenem-resistant Klebsiella pneumoniae (CRKP) strains that demonstrate resistance to multiple antibiotics, including aminoglycosides and tigecycline, in a Chinese hospital.
Methods: A group of ten CRKP strains were collected from the nine patients in a Chinese hospital. Antimicrobial Susceptibility Testing (AST) and phenotypic inhibition assays precisely assess bacterial antibiotic resistance. Real-time quantitative PCR (RT-qPCR) was used to analyze the mRNA levels of efflux pump genes (acrA/acrB and oqxA/oqxB) and the regulatory gene (ramA). The core-genome tree and PFGE patterns were analyzed to assess the clonal and horizontal transfer expansion of the strains. Whole-genome sequencing was performed on a clinical isolate of K. pneumoniae named Kpn20 to identify key resistance genes and antimicrobial resistance islands (ARI).
Results: The CRKP strains showed high resistance to carbapenems, aminoglycosides (CLSI, 2024), and tigecycline (EUCAST, 2024). The mRNA expression levels of efflux pump genes and regulatory genes were detected by RT-qPCR. All 10 isolates had significant differences compared to the control group of ATCC13883. The core-genome tree and PFGE patterns revealed five clusters, indicating clonal and horizontal transfer expansion. Three key resistance genes (blaoxa-232, blaCTX-M-15, and rmtF) were observed in the K. pneumoniae clinical isolate Kpn20. Mobile antibiotic resistance islands were identified containing blaCTX-M-15 and rmtF, with multiple insertion sequences and transposons present. The coexistence of blaoxa-232 and rmtF in a high-risk K. pneumoniae strain was reported. Conjugation assay was utilized to investigate the transferability of blaoxa-232-encoding plasmids horizontally.
Conclusion: The study highlights the emergence of ST15-KL112 high-risk CRKP strains with multidrug resistance, including to aminoglycosides and tigecycline. The presence of mobile ARI and clonal and horizontal transfer expansion of strains indicate the threat of transmission of these strains. Future research is needed to assess the prevalence of such isolates and develop effective control measures.

Keywords: blaOXA-232, rmtF, Klebsiella pneumoniae, carbapenemase, plasmid