Multidrug-Resistant and Carbapenemase Gene-Carrying Acinetobacter colistiniresistens Isolated from Bloodstream Infection.

In this study, we investigated the antimicrobial susceptibility and molecular characteristics of antimicrobial resistance of Acinetobacter colistiniresistens strains isolated from the bloodstream using whole-genome sequencing. Clinical isolates identified as Acinetobacter baumannii and showing colistin resistance at the time of detection were collected. Antimicrobial susceptibility was determined using the VITEK2 system (bioMérieux) and Sensititre system (Thermo Fisher Scientific). Species identification and antimicrobial resistance gene searches were performed through whole-genome sequencing. Through whole-genome sequencing, three colistin-resistant strains from the bloodstream were identified as A. colistiniresistens. All three A. colistiniresistens strains were resistant to two or more antimicrobial agents except for colistin, and two of them were resistant to carbapenems. Genes involved in aminoglycoside [AAC(3)-Ⅱb, AAC(6')-Ⅰj, aadA2, ANT(3″)-Ⅱb, APH(3')-Ⅵa], macrolide (mphD, msrE), carbapenem and cephalosporin (OXA-420, VIM-2), fluoroquinolone and tetracycline (adeF), and sulfonamide (sul1, sul2) resistance were detected. We report multidrug-resistant A. colistiniresistens strains isolated from the bloodstream through whole-genome sequencing. Two strains carried carbapenemase genes, and this is the first report of VIM-2-producing A. colistiniresistens.