Significant Increase in blaNDM-1 Acinetobacter baumannii in a Tertiary Care Greek Hospital Driven by the Dissemination of Established Clones and the Emergence of Novel Lineages

This study aimed to investigate the marked increase in blaNDM-1-positive Acinetobacter baumannii isolates (20% of all CRAB isolates) observed in a tertiary-care hospital in Central Greece during 2025. Thirty blaNDM-1-producing carbapenem-resistant A. baumannii (CRAB) isolates were selected and subjected to whole-genome sequencing for molecular typing and characterization of antimicrobial resistance determinants and virulence-associated genes. The majority of the isolates (22/30) belonged to ST2Pasteur (18 strains), ST85Pasteur (2 strains) and ST2493Pasteur (2 strains), all previously identified in 2023. The remaining eight strains belonged to newly detected STs, such as ST1Pasteur (six strains) and ST2806Pasteur (two strains). All strains carried the blaNDM-1 gene on the Tn7382. The high prevalence of blaNDM-1-positive CRAB represents not only a local threat but also a national concern, as patients from our hospital are frequently transferred to other healthcare facilities or long-term care centers across the country, creating a substantial risk for further dissemination of these strains. Routine molecular screening for blaNDM-1-positive CRAB may represent a valuable strategy for limiting further dissemination.