Characterisation of Carbapenemase-producing Acinetobacter baumannii Isolates from Danish Patients 2014-2021: Detection of a New International Clone-IC11

Objectives: This study aimed to characterise carbapenemase-producing Acinetobacter baumannii ( A. baumannii ) isolates from Danish patients using whole genome sequencing (WGS). It also compared typing and epidemiological data for further investigation of the spread and origin of the carbapenemaseproducing A. baumannii isolates.Methods: From 1 January 2014 to 30 September 2021, 141 carbapenemase-producing A. baumannii isolates, received at the national reference laboratory at Statens Serum Institut, were investigated using WGS. Multilocus sequence typing (ML ST) and cgML ST data, obtained by SeqSphere + software, were linked to data related to source of isolation, patient age and sex, hospital admission and travel history.Results: Most of the carbapenemase-producing A. baumannii isolates were from males ( n = 100, 71%). Most patients ( n = 88, 63%) had travelled outside Scandinavia before admission to a Danish hospital. The most prevalent carbapenemase gene was bla OXA-23 ( n = 124). Isolates belonging to the dominating international clone IC2 accounted for 78% of all isolates. A new international ST164/OXA-91 clone, proposed to be named IC11, was recognised and described. The cgMLST analysis revealed 17 clusters, reflecting both sporadic travel to similar geographical areas and confirmed outbreaks in Danish hospitals.Conclusions: The occurrence of carbapenemase-producing A. baumannii in Denmark was still low; how-ever, isolates belonging to major international clones with a high potential to spread within hospitals, mainly IC2, dominated. OXA-23 was by far the most prevalent carbapenemase detected. Sporadic and travel-related introductions to Danish hospitals, also intra-hospital transmission, could be confirmed, em-phasising the need for continuing vigilance.(C) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/ )

Automated summary

This study used whole genome sequencing (WGS) to characterize carbapenemase-producing Acinetobacter baumannii isolates from Danish patients. The study compared typing and epidemiological data to investigate the spread and origin of these isolates. The results showed that most of the isolates belonged to the international clone IC2 and the most prevalent carbapenemase gene was bla OXA-23. The study confirmed sporadic and travel-related introductions of these isolates to Danish hospitals, highlighting the need for continued vigilance.