Molecular Epidemiology and Persistence of Multidrug-Resistant Acinetobacter baumannii in Zhejiang, China (2015-2020):...

This study investigate the molecular epidemiology and population characteristics of 184 Acinetobacter baumannii clinical isolates collected in Zhejiang (2015-2020), shedding light on the persistence and success of ST208-KL2 lineage.

Whole-genome sequencing and bioinformatic analysis characterized the population structure and transmission dynamics of 184 A. baumannii. Plasmid analysis identified the surrounding structures of blaOXA-58 and blaNDM-1 genes. Serum inhibition assays and Galleria mellonella virulence experiments, combined with global epidemiological analysis, explored the persistence and dominance of ST208-KL2.

Of the isolates, approximately 78.8% (145/184) exhibited carbapenem resistance, primarily driven by blaOXA-23, blaOXA-72, blaOXA-58, and blaNDM-1. The A. baumannii population was divided into 2 clusters, distinguished by differences in ST types and resistance islands profiles. Cluster2 accounted for 71 department-time transmission events, mainly involving long-term interdepartmental spread, particularly in the rehabilitation medicine department and intensive care unit. Recombination analysis revealed that recombination occurred mainly in capsular locus (KL) regions, prophage regions, and predicted protein regions. Phenotypic experiments found that ST208-KL2 isolates displayed increased virulence and greater resistance to serum inhibition compared to ST208-KL7 isolates. This finding likely explains its persistently higher prevalence throughout the study period, except in 2019.

Cluster2 isolates demonstrated significant advantages in ARG prevalence, resistance rates, and transmission capacity. ST208-KL2, with its superior serum resistance and virulence compared to ST208-KL7, has emerged as a dominant lineage with global implications for infection control and public health.