Genomic insights into a Multicenter Outbreak of blaOXA-72-producing carbapenem-resistance Acinetobacter baumannii in Southern Poland

Background: Carbapenem-resistant Acinetobacter baumannii (CRAb) is a major global health concern due to its high morbidity, mortality, and limited treatment options. This study aimed to define the regional genomic epidemiology of CRAb by assessing clonal relatedness, carbapenemase gene distribution, and the plasmid context of blaOXA-72. Methods: In this study, we conducted whole-genome sequencing and core genome multilocus sequence typing (cgMLST) analysis of 70 CRAb isolates collected from multiple hospitals in southern Poland between 2019 and 2022. Results: All isolates were assigned to international clone 2 (IC2), corresponding to sequence type ST2 according to the Pasteur MLST scheme. Genomic analysis revealed the dominance of blaOXA-72 and blaOXA-23 carbapenemase genes. A novel variant, blaOXA-1223, was identified through amino acid sequence analysis. Plasmid analysis revealed that blaOXA-72 was located on a small (~10.9 kb) GR2-type plasmid, consistently present across all blaOXA-72-positive isolates. This study highlights the plasmid-mediated spread of blaOXA-72 and the clonal dissemination of IC2 strains as key drivers of carbapenem resistance in the studied region. Conclusion: Our findings underscore the urgent need for enhanced genomic surveillance and stringent infection control measures to limit the spread of multidrug-resistant Acinetobacter baumannii.