April 21, 2020  |  

Identification of the novel class D ß-lactamase OXA-679 involved in carbapenem resistance in Acinetobacter calcoaceticus.

Authors: Tietgen, Manuela and Kramer, Jan S and Brunst, Steffen and Djahanschiri, Bardya and Wohra, Sonali and Higgins, Paul G and Weidensdorfer, Marko and Riedel-Christ, Sara and Pos, Klaas M and Gonzaga, Aitor and Steglich, Matthias and Nübel, Ulrich and Ebersberger, Ingo and Proschak, Ewgenij and Göttig, Stephan

The aim of this study was to characterize the Acinetobacter calcoaceticus clinical isolate AC_2117 with the novel carbapenem-hydrolysing class D ß-lactamase (CHDL) OXA-679.Identification of the species and ß-lactamases was verified by genome sequencing (PacBio) and phylogenetic analyses. Antibiotic susceptibility of AC_2117 and transformants harbouring cloned blaOXA-679 was evaluated using antibiotic gradient strips and microbroth dilution. OXA-679 was purified heterologously and kinetic parameters were determined using spectrometry or isothermal titration calorimetry. The impact of OXA-679 production during imipenem therapy was evaluated in the Galleria mellonella infection model.Sequencing of the complete genome of the clinical A. calcoaceticus isolate AC_2117 identified a novel CHDL, termed OXA-679. This enzyme shared sequence similarity of 71% to each of the families OXA-143 and OXA-24/40. Phylogenetic analyses revealed that OXA-679 represents a member of a new OXA family. Cloning and expression of blaOXA-679 as well as measurement of kinetic parameters revealed the effective hydrolysis of carbapenems which resulted in reduced susceptibility to carbapenems in Escherichia coli and A. calcoaceticus, and high-level carbapenem resistance in Acinetobacter baumannii. Infection of larvae of G. mellonella with a sublethal dose of blaOXA-679-expressing A. baumannii could not be cured by high-dose imipenem therapy, indicating carbapenem resistance in vivo.We identified blaOXA-679 in a clinical A. calcoaceticus isolate that represents a member of the new OXA-679 family and that conferred high-level carbapenem resistance in vitro and in vivo. © The Author(s) 2019. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For permissions, please email: [email protected]

Journal: The Journal of antimicrobial chemotherapy
DOI: 10.1093/jac/dkz080
Year: 2019

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