Characterization of the novel OXA-213-like β-lactamase OXA-822 from Acinetobacter calcoaceticus

J Antimicrob Chemother. 2021 Feb 11;76(3):626-634. doi: 10.1093/jac/dkaa488.


Objectives: This study analysed the novel carbapenem-hydrolysing class D β-lactamase OXA-822 identified in the clinical Acinetobacter calcoaceticus isolate AC_2117.

Methods: WGS was employed for identification of β-lactamases. Micro-broth dilution was used for evaluation of antibiotic susceptibility of AC_2117 and transformants containing blaOXA-822. After heterologous purification of OXA-822, OXA-359 and OXA-213, enzyme kinetics were determined using spectrometry. The effect of OXA-822 upon meropenem treatment was analysed in the Galleria mellonella in vivo infection model.

Results: OXA-822 is a member of the intrinsic OXA-213-like family found in A. calcoaceticus and Acinetobacter pittii. Amino acid sequence similarity to the nearest related OXA-359 was 97%. Production of OXA-822, OXA-359 and OXA-213 in Acinetobacter baumannii ATCC® 19606T resulted in elevated MICs for carbapenems (up to 16-fold). Penicillinase activity of the purified OXA-822 revealed high KM values, in the millimolar range, combined with high turnover numbers. OXA-822 showed the highest affinity to carbapenems, but affinity to imipenem was ∼10-fold lower compared with other carbapenems. Molecular modelling revealed that imipenem does not interact with a negatively charged side chain of OXA-822, as doripenem does, leading to the lower affinity. Presence of OXA-822 decreased survival of infected Galleria mellonella larvae after treatment with meropenem. Only 52.7% ± 7.7% of the larvae survived after 24 h compared with 90.9% ± 3.7% survival in the control group.

Conclusions: The novel OXA-822 from a clinical A. calcoaceticus isolate displayed penicillinase and carbapenemase activity in vitro, elevated MICs in different species and decreased carbapenem susceptibility in A. baumannii in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acinetobacter
  • Acinetobacter calcoaceticus* / enzymology
  • Acinetobacter calcoaceticus* / genetics
  • Anti-Bacterial Agents / pharmacology
  • Bacterial Proteins* / genetics
  • Carbapenems / pharmacology
  • Microbial Sensitivity Tests
  • beta-Lactamases* / genetics


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Carbapenems
  • beta-Lactamases

Supplementary concepts

  • Acinetobacter pittii