Nosocomial transmission of tet(x3), bla NDM-1 and bla OXA-97-carrying Acinetobacter baumannii conferring resistance to eravacycline and omadacycline, the Netherlands, March to August 2021.

Carbapenem-resistant Acinetobacter baumannii (CRAb) is an important pathogen causing serious nosocomial infections. We describe an outbreak of CRAb in an intensive care unit in the Netherlands in 2021. During an outbreak of non-resistant A. baumannii, while infection control measures were in place, CRAb isolates carrying highly similar bla NDM-1 - and tet(x3)-encoding plasmids were isolated from three patients over a period of several months. The chromosomal and plasmid sequences of the CRAb and non-carbapenemase-carrying A. baumannii isolates cultured from patient materials were analysed using hybrid assemblies of short-read and long-read sequences. The CRAb isolates revealed that the CRAb outbreak consisted of two different strains, carrying similar plasmids. The plasmids contained multiple antibiotic resistance genes including the tetracycline resistance gene tet(x3), and the bla NDM-1 and bla OXA-97 carbapenemase genes. We determined minimal inhibitory concentrations (MICs) for 13 antibiotics, including the newly registered tetracycline antibiotics eravacycline and omadacycline. The CRAb isolates showed high MICs for tetracycline antibiotics including eravacycline and omadacycline, except for minocycline which had a low MIC. In this study we show the value of sequencing multidrug-resistant A. baumannii for outbreak tracking and guiding outbreak mitigation measures.