Emergence of a multidrug-resistant plasmid encoding bla NDM-1, bla OXA-420 and armA in a clinical isolate of Acinetobacter variabilis in Japan

Abstract

Acinetobacter variabilis (formerly genospecies 15 sensu Tjernberg and Ursing) has been isolated from humans and animals and was proposed to be a novel species in 2015. A multidrug-resistant A. variabilis isolate, RYU24, was obtained in 2012 from an inpatient in Okinawa, Japan, with no record of overseas travel. The isolate was resistant to carbapenems, aminoglycosides and ciprofloxacin, with minimum inhibitory concentrations (MICs) of 32 µg ml−1 for imipenem and meropenem; > 1024 µg ml−1 for amikacin, arbekacin, gentamicin and tobramycin; and 8 µg ml−1 for ciprofloxacin. The isolate was found to harbour a 68-kbp plasmid carrying bla NDM-1, which encodes New Delhi metallo-β-lactamase-1 (NDM-1); bla OXA-420, which encodes an OXA-58-like carbapenemase and; armA, which encodes ArmA 16S rRNA methylase conferring pan-aminoglycoside resistance. To our knowledge, this is the first report of a plasmid harbouring the three major drug-resistance genes, bla NDM-1, bla OXA-420 and armA.