Mutations in porin LamB contribute to ceftazidime-avibactam resistance in KPC-producing Klebsiella pneumoniae

Yitan Li,Ying Jiang,Likang Yao,Chao Zhuo,Zhiwei Lin,Baomo Liu,Shunian Xiao,Feifeng Li,Yingyi Guo,Ningjing Liu,Chuyue Zhuo,Xiaoliang Ba,Jiong Wang

doi:10.1080/22221751.2021.1984182

Abstract

Ceftazidime-avibactam (CAZ-AVI) shows promising activity against carbapenem-resistant Klebsiella pneumoniae (CRKP), however, CAZ-AVI resistance have emerged recently. Mutations in KPCs, porins OmpK35 and/or OmpK36, and PBPs are known to contribute to the resistance to CAZ-AVI in CRKP. To identify novel CAZ-AVI resistance mechanism, we generated 10 CAZ-AVI-resistant strains from 14 CAZ-AVI susceptible KPC-producing K. pneumoniae (KPC-Kp) strains through in vitro multipassage resistance selection using low concentrations of CAZ-AVI. Comparative genomic analysis for the original and derived mutants identified CAZ-AVI resistance-associated mutations in KPCs, PBP3 (encoded by ftsI), and LamB, an outer membrane maltoporin. CAZ-AVI susceptible KPC-Kp strains became resistant when complemented with mutated bla KPC genes. Complementation experiments also showed that a plasmid borne copy of wild-type lamB or ftsI gene reduced the MIC value of CAZ-AVI in the induced resistant strains. In addition, bla KPC expression level increased in four of the six CAZ-AVI-resistant strains without KPC mutations, indicating a probable association between increased bla KPC expression and increased resistance in these strains. In conclusion, we here identified a novel mechanism of CAZ-AVI resistance associated with mutations in porin LamB in KPC-Kp.

Highlights

Carbapenem-resistant Klebsiella pneumoniae (CRKP), an opportunistic pathogen spreading worldwide, is increasingly being isolated clinically and has caused numerous nosocomial outbreaks [1,2,3,4]
The minimum inhibitory concentration (MIC) of CAZ-AVI were determined by using the broth microdilution method, and results were interpreted according to the clinical breakpoint recommended by Clinical Laboratory and Standards Institute (CLSI) [31]
Fourteen KPC-KP strains isolated in China were included in this study based on their STs and serotypes [43,44]

Summary

Introduction

Carbapenem-resistant Klebsiella pneumoniae (CRKP), an opportunistic pathogen spreading worldwide, is increasingly being isolated clinically and has caused numerous nosocomial outbreaks [1,2,3,4]. In 2020, 22% of K. pneumoniae strains isolated from patients in China were reported to be carbapenem-resistant [5]. CRKP is resistant to most of the commonly used antimicrobial agents, limiting treatment options and posing a serious threat to the global public health [8]. Carbapenemases are the main causes of multidrug resistance in CRKP and are classified into class A (KPC), class B (NDM, IMP, and VIM), and class D (OXA-48-like) [9]. In China and elsewhere, KPCs are major contributors to carbapenem resistance in K. pneumoniae and more than 70% of carbapenemaseproducing K. pneumoniae produces KPCs [9,10,11]

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