Loss and gain of ceftazidime-avibactam susceptibility in a non-carbapenemase-producing K1-ST23 hypervirulent Klebsiella pneumoniae

ABSTRACT

Objectives

This study aimed at revealing the underlying mechanisms of the loss and gain of ceftazidime-avibactam susceptibility in a non-carbapenemase-producing hypervirulent Klebsiella pneumoniae (hvKp).

Methods

Here we longitudinally recovered 3 non-carbapenemase-producing K1-ST23 hvKp strains at a one-month interval (KP29105, KP29499 and KP30086) from an elderly male. Antimicrobial susceptibility testing, whole genome sequencing, transcriptomic sequencing, gene cloning, plasmid conjugation, quantitative real-time PCR (qRT-PCR), and SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) were conducted.

Results

Among the 3 hvKp strains, KP29105 was resistant to the third- and fourth-generation cephalosporins, KP29499 acquired resistance to both ceftazidime-avibactam and carbapenems, while KP30086 restored its susceptibility to ceftazidime-avibactam, imipenem and meropenem but retained low-level resistance to ertapenem. KP29105 and KP29499 carried plasmid-encoded genes bla_CTX-M-15 and bla_CTX-M-71, respectively, but KP30086 lost both. Cloning of gene bla_CTX-M-71 and conjugation experiment of bla_CTX-M-71-carrying plasmid showed that the transformant and transconjugant were susceptible to ceftazidime-avibactam but had a more than 8-fold increase in MICs. Supplementation with an outer membrane permeabilizer could reduce the MIC of ceftazidime-avibactam by 32 folds, indicating that porins play a key role in ceftazidime-avibactam resistance. The OmpK35 of the 3 isolates was not expressed, and the OmpK36 of KP29499 and KP30086 had a novel amino acid substitution (L359R). SDS-PAGE and qRT-PCR showed that the expression of porin OmpK36 of KP29499 and KP30086 was significantly down-regulated compared with KP29105.

Conclusions

In summary, we reported the rare ceftazidime-avibactam resistance in a non-carbapenemase-producing hvKp strain. Resistance plasmid carrying bla_CTX-M-71 and mutated OmpK36 had a synergetic effect on the resistance.

KEYWORDS:

• Hypervirulent Klebsiella pneumoniae
• ceftazidime-avibactam resistance
• CTX-M-71
• OmpK36
• non-carbapenemase-producing strain

Acknowledgements

We would like to thank all our colleagues in the Laboratory of Clinical Microbiology and Infectious Diseases for their assistance.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data Availability statement

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials.

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/21505594.2024.2348251

Additional information

Funding

This work was supported by the Elite Medical Professionals Project of China-Japan Friendship Hospital [grant number ZRJY2023-QM32]; National Natural Science Foundation of China [grant number 82102456]; Chinese Academy of Medical Sciences CAMS Innovation Fund for Medical Sciences [grant number CIFMS 2021-I2M-1-048 and CIFMS 2021-I2M-1-030]; National High Level Hospital Clinical Research Funding [grant number 2022-NHLHCRF-LX-01].