Increased gene expression and copy number of mutated blaKPC lead to high-level ceftazidime/avibactam resistance in Klebsiella pneumoniae

Bin Cao,Yingmei Liu,Lingxiao Sun,Qi Wang,Haibo Li

doi:10.1186/s12866-021-02293-0

Abstract

BackgroundResistance to ceftazidime-avibactam was reported, and it is important to investigate the mechanisms of ceftazidime/avibactam resistance in K. pneumoniae with mutations in blaKPC.ResultsWe report the mutated blaKPC is not the only mechanism related to CZA resistance, and investigate the role of outer porin defects, efflux pump, and relative gene expression and copy number of blaKPC and ompk35/36. Four ceftazidime/avibactam-sensitive isolates detected wild type blaKPC-2, while 4 ceftazidime/avibactam-resistant isolates detected mutated blaKPC (blaKPC-51, blaKPC-52, and blaKPC-33). Compared with other ceftazidime/avibactam-resistant isolates with the minimal inhibitory concentration of ceftazidime/avibactam ranging 128–256 mg/L, the relative gene expression and copy number of blaKPC was increased in the isolate which carried blaKPC-51 and also showed the highest minimal inhibitory concentration of ceftazidime/avibactam at 2048 mg/L. The truncated Ompk35 contributes rare to ceftazidime/avibactam resistance in our isolates. No significant difference in minimal inhibitory concentration of ceftazidime/avibactam was observed after the addition of PABN.ConclusionsIncreased gene expression and copy number of mutated blaKPC can cause high-level ceftazidime/avibactam resistance.

Highlights

Resistance to ceftazidime-avibactam was reported, and it is important to investigate the mechanisms of ceftazidime/avibactam resistance in K. pneumoniae with mutations in blaKPC
The transformed E.coli isolates carrying mutated blaKPC manifested increased CZA minimal inhibitory concentration (MIC) compared with the WT blaKPC-2 transformant
In our report, we demonstrate a new mechanism of high-level CZA resistance in a K. pneumoniae carbapenemases (KPCs)-producing K. pneumoniae strain in a lung transplant recipient, which is that high-level resistance to CZA is due to increased gene expression and copy number of the mutated blaKPC

Summary

Introduction

Resistance to ceftazidime-avibactam was reported, and it is important to investigate the mechanisms of ceftazidime/avibactam resistance in K. pneumoniae with mutations in blaKPC. Ceftazidime/avibactam (CZA) has been considered a promising β-lactam-β-lactamase inhibitor combination with activity against serine β-lactamases, including KPCs [2]. Mechanisms of CZA resistance have reported in several studies, including specific mutations in the blaKPC gene [4], specific mutations in the blaCTX-M gene [17], porin deficiency combined with high ceftazidime hydrolysis [19, 20], or porin inactivation with increased expression of the blaKPC gene [21, 22]. The mechanism most often associated with the emergence of CZA resistance after treatment has been observed to be mutations in the blaKPC gene encoding for KPC enzymes [4,5,6,7,8,9,10,11,12]. The most common amino acid substitution of KPC was D179Y in KPC-2 (KPC-33) [6] and KPC-3 (KPC-31) [4]

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