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Genetic basis of antimicrobial resistance, virulence features and phylogenomics of carbapenem-resistant Acinetobacter baumannii clinical isolates

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The worldwide emergence and clonal spread of carbapenem-resistant Acinetobacter baumannii (CRAB) is of great concern. In the present study, we determined the mechanisms of antimicrobial resistance, virulence gene repertoire and genomic relatedness of CRAB isolates circulating in Serbian hospitals.


CRAB isolates were analyzed using whole-genome sequencing (WGS) for the presence of antimicrobial resistance-encoding genes, virulence factors-encoding genes, mobile genetic elements and genomic relatedness. Antimicrobial susceptibility testing was done by disk diffusion and broth microdilution methods.


Eleven isolates exhibited an MDR resistance phenotype, while four of them were XDR. MIC90 for meropenem and imipenem were > 64 µg/mL and 32 µg/mL, respectively. While all CRABs harbored blaOXA−66 variant of blaOXA−51 gene, those assigned to STPas2, STPas636 and STPas492 had blaADC−73,blaADC−74 and blaADC−30 variants, respectively. The following acquired carbapenemases-encoding genes were found: blaOXA−72 (n = 12), blaOXA−23 (n = 3), and blaNDM−1(n = 5), and were mapped to defined mobile genetic elements. MLST analysis assigned the analyzed CRAB isolates to three Pasteur sequence types (STs): STPas2, STPas492, and STPas636. The Majority of strains belonged to International Clone II (ICII) and carried tested virulence-related genes liable for adherence, biofilm formation, iron uptake, heme biosynthesis, zinc utilization, serum resistance, stress adaptation, intracellular survival and toxin activity.


WGS elucidated the resistance and virulence profiles of CRABs isolated from clinical samples in Serbian hospitals and genomic relatedness of CRAB isolates from Serbia and globally distributed CRABs.

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Data availability

All data generated or analysed during this study are included in this published article.


Acb complex:

Acinetobacter calcoaceticus-baumannii complex


Ambler Class C


Clinical and Laboratory Standards Institute


Carbapenem-resistant A. baumannii


International Clones


Intensive Care Units






Minimum Inhibitory Concentrations


Multilocus Sequence Typing


National Center for Biotechnology Information






Single-Nucleotide Polymorphisms


Sequence Types


Whole Genome Sequencing


Extensively Drug-Resistant


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This work was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia [Grant No. 451-03-68/2022-14/200110 and Grant No. 451-03-47/2023-01/ 200178 and Grant No. 451-03-47/2023-01/ 200007], and Science Fund of the Republic of Serbia [Grant No. 7042, Tracking antimicrobial resistance in diverse ecological niches - one health perspective- TRACE].

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Authors and Affiliations



BL conceptualized the study, performed experiments and wrote the manuscript. JK carried out the experiments, performed bioinformatic analysis, and visualized obtained data. MD performed bioinformatic analysis and visualized obtained data. SK performed bioinformatic analysis. ID carried out the experiments. BJ criticaly reviewed of the manuscript. IG designed the study, visualized obtained data, revised the manuscript. All authors have read and agreed with the final version of the manuscript.

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Correspondence to Bojana Lukovic.

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The study was approved by the ethical committee of the Medical Faculty, University of Belgrade (1550/II-4).

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The authors declare no competing interests.

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Lukovic, B., Kabic, J., Dragicevic, M. et al. Genetic basis of antimicrobial resistance, virulence features and phylogenomics of carbapenem-resistant Acinetobacter baumannii clinical isolates. Infection (2024).

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