Whole genome sequencing insight into carbapenem-resistant and multidrug-resistant Acinetobacter baumannii harboring chromosome-borne bla OXA-23 .

Carbapenem-resistant Acinetobacter baumannii (CRAB) poses a significant threat to hospitalized patients as effective therapeutic options are scarce. Based on the genomic characteristics of the CRAB strain AB2877 harboring chromosome-borne bla _OXA-23 , which was isolated from the bronchoalveolar lavage fluid (BALF) of a patient in a respiratory intensive care unit (RICU), we systematically analyzed antibiotic resistance genes (ARGs) and the genetic context associated with ARGs carried by CRAB strains harboring chromosome-borne bla _OXA-23 worldwide. Besides bla _OXA-23 , other ARGs were detected on the chromosome of the CRAB strain AB2877 belonging to ST208/1806 (Oxford MLST scheme). Several key genetic contexts associated with the ARGs were identified on the chromosome of the CRAB strain AB2877, including (1) the MDR region associated with bla _OXA-23 , tet(B)-tetR(B ), aph(3'')-Ib, and aph(6)-Id (2); the resistance island AbGRI3 harboring armA and mph(E)-msr(E ) (3); the Tn 3 -like composite transposon containing bla _TEM-1D and aph(3')-Ia ; and (4) the structure "IS Aba1-bla _ADC-25 ." The first two genetic contexts were most common in ST195/1816, followed by ST208/1806. The last two genetic contexts were found most frequently in ST208/1806, followed by ST195/1816.IMPORTANCEThe bla _OXA-23 gene can be carried by plasmid or chromosome, facilitating horizontal genetic transfer and increasing carbapenem resistance in healthcare settings. In this study, we focused on the genomic characteristics of CRAB strains harboring the chromosome-borne bla _OXA-23 gene, and the important genetic contexts associated with bla _OXA-23 and other ARGs were identified, and their prevalent clones worldwide were determined. Notably, although the predominant clonal CRAB lineages worldwide containing the MDR region associated with bla _OXA-23 , tet(B)-tetR(B ), aph(3'')-Ib, and aph (6)-Id was ST195/1816, followed by ST208/1806, the CRAB strain AB2877 in our study belonged to ST208/1806. Our findings contribute to the knowledge regarding the dissemination of CRAB strains and the control of nosocomial infection.
Competing Interests: The authors declare no conflict of interest.