Genomics unveils country-to-country transmission between animal hospitals of a multidrug-resistant and sequence type 2 Acinetobacter baumannii clone

<i>Acinetobacter baumannii</i> is a globally distributed opportunistic pathogen in human health settings, including in intensive care units (ICUs). We investigated the contamination of a French small animal ICU with <i>A. baumannii</i>. We discovered repeated animal contamination by <i>A. baumannii</i>, and phylogenetic analysis traced contamination back to a potential foreign animal origin. Genomic analysis combined with antibiotic susceptibility testing revealed heteroresistance to penicillin and aminoglycoside mediated by insertion sequence dynamics and also suggest a potential cross-resistance to human-restricted piperacillin-tazobactam combination. The <i>A. baumannii</i> isolates of the animal ICU belong to the International Clone 2 commonly found in human health settings. Our results suggest a high adaptation of this lineage to healthcare settings and provide questions on the requirements for genetic determinants enabling adaptation to host and abiotic conditions.