International high-risk clones of Acinetobacter baumannii in Genbank: analysis of 47 738 whole-genome sequences

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Introduction. Acinetobacter baumannii is a major cause of hospital-acquired infections and is frequently associated with multidrug resistance, particularly among international clones of high risk (ICs), whose identification within the hospital is important for risk assessment. Since our previous analysis of the Genbank database, the number of genomes has increased threefold, while the number of recognized ICs has expanded to 12, making an updated analysis necessary. Objective. To analyze A. baumannii genomes deposited in Genbank in order to identify ICs and to characterize antimicrobial resistance determinants, virulence factors, and plasmid replicons. Materials and methods. A total of 47,738 A. baumannii whole-genome sequences available in Genbank as of March 10, 2026, were included in the study. Isolates were typed using the Pasteur MLST scheme, cgMLST profiles, and OXA-51-like carbapenemase variants using ResFinder, Kaptive, and MentaList. Statistical analysis was conducted using nonparametric methods with Holm correction. Results. Overall, 76.3% of isolates were assigned to IC1-IC12. IC2 was the predominant clone, accounting for 66.0% of all genomes and 86.5% of IC isolates. In total, 1,067 sequence types, 156 OXA-51-like variants, 236 KL types, and 22 OCL types were identified. IC isolates carried significantly more resistance genes than non-IC isolates; for IC2, IC5, IC7, and IC1, the excess was approximately 1.7- to 1.8-fold. Distinct clone-specific associations with carbapenemases were observed: NDM in IC11, IC9, and IC1, and GES in IC12 and IC9. Conclusions. This large-scale genomic analysis confirmed the predominance of ICs within the Genbank A. baumannii population and their key role in the accumulation of antimicrobial resistance determinants. The resulting database may support molecular surveillance, comparative genomic studies, and detection of emerging epidemic clones. The database is available at: https://doi.org/10.5281/zenodo.10143377.

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