The Molecular Characterization of bla(NDM-1)-Positive Acinetobacter baumannii Isolated in Central Greece

The objective of the present study is to report the detection and the molecular characterization of nine bla(NDM-1)-positive Acinetobacter baumannii isolates, which were isolated from patients in a tertiary care hospital in Central Greece from December 2022 to August 2023. The isolates were characterized by whole genome sequencing to obtain Pasteur multilocus sequencing typing (MLST) and to identify the bla(NDM-1)-environment, resistome, and virulence genes content. In silico MLST analysis showed that the isolates belonged to four different clones (STs 160, 2, 85, and 2493). All strains, apart from the bla(NDM-1)-gene, possessed at least eight different genes, encoding resistance to various antimicrobial agents. Whole genome sequencing revealed two different structures of the bla(NDM-1) environment. The first, detected in ST160 strain, was identical with the Tn125, whereas the second, found in STs 2, 85, and 2493 was associated with Tn7382. To our knowledge, after a sole strain reported in 2016 and imported by a patient hospitalized in a Libyan hospital, this is the first report of the emergence of polyclonal bla(NDM-1)-positive Acinetobacter baumannii in Greece. Our findings re-emphasize the need to apply diligent surveillance protocols in order to limit the horizontal transfer of the bla(NDM-1) gene to other A. baumannii clones or to other recipient strains.