The objective of this study was the phenotypic and genotypic characterization of a carbapenem resistant Acinetobacter baumannii (CRAB) isolate. The isolate, recovered in Northern Spain in 2019, was identified by MALDI-TOF to the species level. Antimicrobial susceptibility testing was performed using the Phoenix BD NMIC-502 Panel, E-test, and broth microdilution methods. The presence of a metallo-β-lactamase (MBL) was verified by PCR and immunochromatographic assays. The genetic location of the MBL was confirmed using S1-pulsed-field gel electrophoresis (S1-PFGE) followed by Southern blot hybridization. Whole genome sequencing (WGS) was completed using the Miseq and MinION platforms, followed by core-genome MLST (cgMLST) and seven-locus MLST analysis. The CRAB was assigned ST85 (Pasteur scheme) and ST957 (Oxford scheme) representing international clone (IC) 9 and harbored the intrinsic β-lactamase OXA-94 with ISAba1 upstream of it, and the MBL bla NDM-6. Hybridization experiments revealed that the bla NDM-6 was encoded on the chromosome. Using WGS the bla NDM-6 environment could be identified arranged in the following order: ISAba14, aphA6, ISAba125, bla NDM-6, ble MBL, trpF, dsbC, cutA, and ISAba14. Downstream, a 10,462 bp duplication was identified, including a second copy of bla NDM-6 in the following genetic composition: ISAba125, bla NDM-6, ble MBL, trpF, dsbC, cutA, and ISAba14. To our knowledge, this is the first description of bla NDM-6 in A. baumannii. The MBL was present in two copies in the chromosome in a new genetic environment associated with IS elements highlighting the contribution of mobile genetic elements in the dissemination of this gene.
Keywords: Acinetobacter baumannii; NDM-6; carbapenemase; long reads; whole genome sequencing.
Copyright © 2020 Xanthopoulou, Urrutikoetxea-Gutiérrez, Vidal-Garcia, Diaz de Tuesta del Arco, Sánchez-Urtaza, Wille, Seifert, Higgins and Gallego.