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Targeting Multidrug-Resistant Acinetobacter spp.: Sulbactam and the Diazabicyclooctenone β-Lactamase Inhibitor ETX2514 as a Novel Therapeutic Agent.

  • Barnes, Melissa D1, 2
  • Kumar, Vijay3
  • Bethel, Christopher R1
  • Moussa, Samir H4
  • O'Donnell, John4
  • Rutter, Joseph D1
  • Good, Caryn E5
  • Hujer, Kristine M1, 2
  • Hujer, Andrea M1, 2
  • Marshall, Steve H1
  • Kreiswirth, Barry N6
  • Richter, Sandra S7
  • Rather, Philip N8, 9
  • Jacobs, Michael R2, 5
  • Papp-Wallace, Krisztina M1, 2, 3
  • van den Akker, Focco10
  • Bonomo, Robert A11, 2, 3, 12, 13, 14, 15, 16
  • 1 Louis Stokes Cleveland Veterans Affairs Medical Center Research Service, Cleveland, Ohio, USA.
  • 2 Department of Medicine, Case Western Reserve University, Cleveland, Ohio, USA.
  • 3 Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, USA.
  • 4 Entasis Therapeutics, Waltham, Massachusetts, USA.
  • 5 Department of Pathology, University Hospitals, Cleveland Medical Center, Cleveland, Ohio, USA.
  • 6 Public Health Research Institute Tuberculosis Center, New Jersey Medical School, Rutgers University, Newark, New Jersey, USA. , (Jersey)
  • 7 Cleveland Clinic Foundation, Cleveland, Ohio, USA.
  • 8 Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA. , (Georgia)
  • 9 Research Service, Atlanta Veterans Affairs Medical Center, Decatur, Georgia, USA. , (Georgia)
  • 10 Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, USA [email protected] [email protected]
  • 11 Louis Stokes Cleveland Veterans Affairs Medical Center Research Service, Cleveland, Ohio, USA [email protected] [email protected]
  • 12 Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio, USA.
  • 13 Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA.
  • 14 Department of Proteomics and Bioinformatics, Case Western Reserve University, Cleveland, Ohio, USA.
  • 15 CWRU-Cleveland VAMC Center for Antimicrobial Resistance and Epidemiology (Case VA CARES), Cleveland, Ohio, USA.
  • 16 Geriatric Research Education and Clinical Centers (GRECC), Louis Stokes Cleveland Department of Veterans Affairs, Cleveland, Ohio, USA.
Published Article
American Society for Microbiology
Publication Date
Mar 12, 2019
DOI: 10.1128/mBio.00159-19
PMID: 30862744


Multidrug-resistant (MDR) Acinetobacter spp. poses a significant therapeutic challenge in part due to the presence of chromosomally encoded β-lactamases, including class C Acinetobacter-derived cephalosporinases (ADC) and class D oxacillinases (OXA), as well as plasmid-mediated class A β-lactamases. Importantly, OXA-like β-lactamases represent a gap in the spectrum of inhibition by recently approved β-lactamase inhibitors such as avibactam and vaborbactam. ETX2514 is a novel, rationally designed, diazabicyclooctenone inhibitor that effectively targets class A, C, and D β-lactamases. We show that addition of ETX2514 significantly increased the susceptibility of clinical Acinetobacter baumannii isolates to sulbactam. AdeB and AdeJ were identified to be key efflux constituents for ETX2514 in A. baumannii The combination of sulbactam and ETX2514 was efficacious against A. baumannii carrying bla TEM-1, bla ADC-82, bla OXA-23, and bla OXA-66 in a neutropenic murine thigh infection model. We also show that, in vitro, ETX2514 inhibited ADC-7 (k 2/Ki 1.0 ± 0.1 × 106 M-1 s-1) and OXA-58 (k 2/Ki 2.5 ± 0.3 × 105 M-1 s-1). Cocrystallization of ETX2514 with OXA-24/40 revealed hydrogen bonding interactions between ETX2514 and residues R261, S219, and S128 of OXA-24/40 in addition to a chloride ion occupied in the active site. Further, the C3 methyl group of ETX2514 shifts the position of M223. In conclusion, the sulbactam-ETX2514 combination possesses a broadened inhibitory range to include class D β-lactamases as well as class A and C β-lactamases and is a promising therapeutic candidate for infections caused by MDR Acinetobacter spp.IMPORTANCE The number and diversity of β-lactamases are steadily increasing. The emergence of β-lactamases that hydrolyze carbapenems poses a significant threat to our antibiotic armamentarium. The explosion of OXA enzymes that are carbapenem hydrolyzers is a major challenge (carbapenem-hydrolyzing class D [CHD]). An urgent need exists to discover β-lactamase inhibitors with class D activity. The sulbactam-ETX2514 combination demonstrates the potential to become a treatment regimen of choice for Acinetobacter spp. producing class D β-lactamases.

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