期刊
ANTIMICROBIAL AGENTS AND CHEMOTHERAPY
卷 66, 期 4, 页码 -出版社
AMER SOC MICROBIOLOGY
DOI: 10.1128/aac.02124-21
关键词
Klebsiella pneumoniae; D179Y; ceftazidime-avibactam resistance; antibiotic resistance; KPC; KPC D179Y; beta-lactamases
资金
- Cleveland Department of Veterans Affairs from the Biomedical Laboratory Research & Development Service of the VA Office of Research and Development [1I01BX001974]
- Geriatric Research Education and Clinical Center VISN 10
- National Institute of Allergy and Infectious Diseases of the National Institutes of Health (NIH) [R21AI142049]
- Merck Sharp & Dohme, Corp., Kenilworth, NJ [MISP 57394]
This study investigates the susceptibility and resistance mechanism of D179Y variant of KPC-2 and -3 to carbapenems and ceftazidime and ceftazidime-avibactam, and it reveals that conformational changes and overall disorder caused by D179Y substitution contribute to the unexpected phenotype.
beta-Lactamase-mediated resistance to ceftazidime-avibactam (CZA) is a serious limitation in the treatment of Gram-negative bacteria harboring Klebsiella pneumoniae carbapenemase (KPC). Herein, the basis of susceptibility to carbapenems and resistance to ceftazidime (CAZ) and CZA of the D179Y variant of KPC-2 and -3 was explored. First, we determined that resistance to CZA in a laboratory strain of Escherichia coli DH10B was not due to increased expression levels of the variant enzymes, as demonstrated by reverse transcription PCR (RT-PCR). Using timed mass spectrometry, the D179Y variant formed prolonged acyl-enzyme complexes with imipenem (IMI) and meropenem (MEM) in KPC-2 and KPC-3, which could be detected up to 24 h, suggesting that IMI and MEM act as covalent beta-lactamase inhibitors more than as substrates for D179Y KPC-2 and -3. This prolonged acyl-enzyme complex of IMI and MEM by D179Y variants was not observed with wild-type (WT) KPCs. CAZ was studied and the D179Y variants also formed acyl-enzyme complexes (1 to 2 h). Thermal denaturation and differential scanning fluorimetry showed that the tyrosine substitution at position 179 destabilized the KPC beta-lactamases (KPC-2/3 melting temperature [T-m] of 54 to 55 degrees C versus D179Y T-m of 47.5 to 51 degrees C), and the D179Y protein was 3% disordered compared to KPC-2 at 318 K. Heteronuclear H-1/N-15-heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectroscopy also revealed that the D179Y variant, compared to KPC-2, is partially disordered. Based upon these observations, we discuss the impact of disordering of the omega loop as a consequence of the D179Y substitution. These conformational changes and disorder in the overall structure as a result of D179Y contribute to this unanticipated phenotype.
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