Understanding the dynamics of imipenem-resistant Acinetobacter baumannii lineages within Portugal

A recent collection of 213 imipenem-resistant Acinetobacter baumannii (IRAB) clinical isolates was characterized for the presence of acquired carbapenem-hydrolysing class D β-lactamases (CHDLs) and clonality. A population structure analysis of IRAB was also conducted, with five molecular typing methods. Three main clusters, each one associated with a specific CHDL, were observed with multilocus sequence typing. Overall, our results suggest a switch in the dominant clone, with sequence type (ST) 92, carrying blaOXA-23 (63.4%), replacing the closely related ST98, carrying blaOXA-24/40 (22%). In addition, ST103, an independent lineage, was associated with blaOXA-58-carrying isolates (14.6%).