Effects of KPC variant and porin genotype on the in vitro activity of meropenem-vaborbactam against carbapenem-resistant Enterobacteriaceae

William R. Wilson, Ellen G. Kline, Chelsea E. Jones, Kristin T. Morder, Roberta T. Mettus, Yohei Doi, M. Hong Nguyen, Cornelius J. Clancy, Ryan K. Shields

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Abstract

Meropenem-vaborbactam is a new agent with the potential to treat carbapenem-resistant Enterobacteriaceae (CRE) infections. We describe the in vitro activity of meropenem-vaborbactam against representative CRE genotypes and laboratory-engineered Escherichia coli isolates harboring mutant blaKPC genes associated with ceftazidime-avibactam resistance. We also compared disk diffusion and gradient strip testing methods to standard broth microdilution methods. Against 120 CRE isolates, median ceftazidime-avibactam and meropenem-vaborbactam MICs were 1 and 0.03 g/ml, respectively. Ninety-eight percent (117/120) of isolates were susceptible to meropenem-vaborbactam (MICs 4 g/ml). Against Klebsiella pneumoniae isolates harboring mutant blaKPC, the addition of vaborbactam lowered the meropenem MICs in 78% of isolates (14/18); 100% were susceptible to meropenem-vaborbactam. Median meropenem-vaborbactam MICs were higher against K. pneumoniae carbapenemase (KPC)-producing K. pneumoniae isolates with mutant ompK36 porin genes (n 26) than against those with wild-type ompK36 porin genes (n 54) (0.25 versus 0.03 g/ml; P 0.0001). Against E. coli TOP10 isolates with plasmid constructs containing wild-type blaKPC or mutant blaKPC, the addition of vaborbactam at 8 g/ml lowered the meropenem MICs 2- to 512-fold, resulting in meropenem-vaborbactam MICs of 0.03 g/ml. The rates of categorical agreement with broth microdilution for disk diffusion or gradient strips ranged from 90 to 95%. Essential agreement rates were higher for research-use-only (RUO) gradient strips manufactured by bioMérieux (82%) than for those manufactured by Liofilchem (48%) (P 0.0001). Taken together, our data highlight the potent in vitro activity of meropenem-vaborbactam against CRE, including isolates resistant to ceftazidime-avibactam. Vaborbactam inhibited both wild-type and variant KPC enzymes. On the other hand, KPC-producing K. pneumoniae isolates with ompK36 mutations displayed higher meropenem-vaborbactam MICs than isolates with wild-type ompK36. The results of susceptibility testing with RUO bioMérieux gradient strips most closely aligned with those of broth microdilution methods.

Original languageEnglish
Article numbere02048-18
JournalAntimicrobial agents and chemotherapy
Volume63
Issue number3
DOIs
Publication statusPublished - 03-2019
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • Pharmacology (medical)
  • Infectious Diseases

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    Wilson, W. R., Kline, E. G., Jones, C. E., Morder, K. T., Mettus, R. T., Doi, Y., Nguyen, M. H., Clancy, C. J., & Shields, R. K. (2019). Effects of KPC variant and porin genotype on the in vitro activity of meropenem-vaborbactam against carbapenem-resistant Enterobacteriaceae. Antimicrobial agents and chemotherapy, 63(3), [e02048-18]. https://doi.org/10.1128/AAC.02048-18