ABSTRACTAcinetobacter baumanniiis an antibiotic-resistant, Gram-negative pathogen that causes a multitude of nosocomial infections. However, pathogenicity mechanisms and the host cell response during infection remain unclear. In this study, we determined virulence traits ofA. baumanniiclinical isolates belonging to the most widely disseminated international clonal lineage, international cluster 2 (IC2),in vitroandin vivo. Complexome profiling of primary human endothelial cells withA. baumanniirevealed that mitochondria, and in particular complexes of the electron transport chain, are important host cell targets. Infection with highly virulentA. baumanniiremodelled assembly of mitochondrial protein complexes and led to metabolic adaptation. These were characterized by reduced mitochondrial respiration and glycolysis in contrast to those observed in infection with low-pathogenicityA. baumannii. Perturbation of oxidative phosphorylation, destabilization of mitochondrial ribosomes, and interference with mitochondrial metabolic pathways were identified as important pathogenicity mechanisms. Understanding the interaction of human host cells with the current globalA. baumanniiclone is the basis to identify novel therapeutic targets.IMPORTANCEVirulence traits ofAcinetobacter baumanniiisolates of the worldwide most prevalent international clonal lineage, IC2, remain largely unknown. In our study, multidrug-resistant IC2 clinical isolates differed substantially in their virulence potential despite their close genetic relatedness. Our data suggest that, at least for some isolates, mitochondria are important target organelles during infection of primary human endothelial cells. Complexes of the respiratory chain were extensively remodelled after infection with a highly virulentA. baumanniistrain, leading to metabolic adaptation characterized by severely reduced respiration and glycolysis. Perturbations of both mitochondrial morphology and mitoribosomes were identified as important pathogenicity mechanisms. Our data might help to further decipher the molecular mechanisms ofA. baumanniiand host mitochondrial interaction during infection.