We characterized by whole-genome sequencing (WGS) six carbapenem-resistant Acinetobacter baumannii strains isolated from a Brazilian tertiary hospital during a 14-day period. The ISAba1-blaOXA-23 structure was found in the chromosome of five isolates, whereas blaOXA-72 was inserted in a 16.6-kb plasmid in two isolates. The presence of ISAba1-blaADC-like justified the high broad-spectrum cephalosporins minimal inhibitory concentrations (MICs) (MIC50, > 512 mg/L) verified in all isolates. Only minocycline (MIC50, ≤ 0.5 μg/mL), polymyxin B (MIC50, 0.5 μg/mL), and tigecycline (MIC50, 0.5 μg/mL) were in vitro active against such isolates. A diversity of other antimicrobial resistance determinants (aph(3')-VIa, aadA1, aac(3')-IIa, strA, strB, sul2, drfA1, mph(E), msr(E), tetB, and floR) was also observed, which may confer resistance to at last six distinct antimicrobial classes. Four distinct pulsed-field gel electrophoresis (PFGE) profiles were observed during the study period, which belonged to ST79/ST258 (n = 2; IC5), ST25/ST229 (n = 2; IC7), ST1 (n = 1; IC1), and ST162/ST235 (n = 1; IC4). Although the ST1 isolate that carried blaOXA-23 and blaOXA-72 was introduced in this hospital setting by a transferred patient, two clonally related ST79/ST258 isolates carrying either one of these carbapenemase encoding genes were recovered from two patients who were hospitalized within the same period of time in the same hospital unit. Finally, a good correlation between PFGE/MLST, blaOXA-51 variant, and single nucleotide polymorphisms was also observed. Here we demonstrated that distinct extensively drug-resistant A. baumannii clones can circulate in the same hospital setting during a short time period, illustrating a very complex epidemiological scenario for this priority pathogen.
Keywords: Acinetobacter baumannii; antimicrobial resistance determinants; extensively drug resistant; hospital setting; minocycline; whole-genome sequencing.