Weihua Han,1,* Peiyao Zhou,2,* Chun Chen,3,* Chunyang Wu,2 Li Shen,1 Cailing Wan,4 Yanghua Xiao,4 Jiao Zhang,2 Bingjie Wang,1 Junhong Shi,1 Xinru Yuan,1 Haojin Gao,1 Hongxiu Wang,1 Ying Zhou,1 Fangyou Yu1 

1Department of Clinical Laboratory, Shanghai Pulmonary Hospital, School of Medicine, Tongji University, Shanghai, People’s Republic of China; 2Department of Laboratory Medicine, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, People’s Republic of China; 3Cancer Center, Department of Pulmonary and Critical Care Medicine, Zhejiang Provincial People’s Hospital, Affiliated People’s Hospital, Hangzhou Medical College, Hangzhou, People’s Republic of China; 4School of Public Health, Nanchang University, Nanchang, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Ying Zhou; Fangyou Yu, Email 18702195157@163.com; wzjxyfy@163.com

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections are a great threat to public health worldwide. Ceftazidime-avibactam (CZA) is an effective β-lactam/β-lactamase inhibitors against CRKP. However, reports of resistance to CZA, mainly caused by Klebsiella pneumoniae carbapenemase (KPC) variants, have increased in recent years. In this study, we aimed to describe the resistance characteristics of KPC-12, a novel KPC variant identified from a CZA resistant K. pneumoniae.
Methods: The K. pneumoniae YFKP-97 collected from a patient with respiratory tract infection was performed whole-genome sequencing (WGS) on the Illumina NovaSeq 6000 platform. Genomic characteristics were analyzed using bioinformatics methods. Antimicrobial susceptibility testing was conducted by the broth microdilution method. Induction of resistant strain was carried out in vitro as previously described. The G. mellonella killing assay was used to evaluate the pathogenicity of strains, and the conjugation experiment was performed to evaluate plasmid transfer ability.
Results: Strain YFKP-97 was a multidrug-resistant clinical ST11-KL47 K. pneumoniae confers high-level resistance to CZA (16/4 μg/mL). WGS revealed that a KPC variant, KPC-12, was carried by the IncFII (pHN7A8) plasmids (pYFKP-97_a and pYFKP-97_b) and showed significantly decreased activity against carbapenems. In addition, there was a dose-dependent effect of blaKPC-12 on its activity against ceftazidime. In vitro inducible resistance assay results demonstrated that the KPC-12 variant was more likely to confer resistance to CZA than the KPC-2 and KPC-3 variants.
Discussion: Our study revealed that patients who was not treated with CZA are also possible to be infected with CZA-resistant strains harbored a novel KPC variant. Given that the transformant carrying blaKPC-12 was more likely to exhibit a CZA-resistance phenotype. Therefore, it is important to accurately identify the KPC variants as early as possible.

Keywords: carbapenem-resistant Enterobacterales, Klebsiella pneumoniae, ceftazidime-avibactam, KPC-12, carbapenemase