Characterization and genomic analysis of the highly virulent Acinetobacter baumannii ST1791 strain dominating in Anhui, China

The multidrug-resistant Acinetobacter baumannii clonal complex 92 is spreading worldwide due to its high-frequency gene mutation and recombination, posing a significant threat to global medical and health safety. Between November 2021 and April 2022, a total of 132 clinical A. baumannii isolates were collected from a tertiary hospital in China. Their growth ability and virulence of these isolates were assessed using growth curve analyses and the Galleria mellonella infection model. The genetic characteristics of the isolates were further examined through whole-genome sequencing. ST1791^O/ST2^P isolates represented the largest proportion of isolates in our collection and exhibited the highest growth rate and strongest virulence among all sequence types (STs) analyzed. Whole-genome sequences from 14,159 clinical isolates were collected from the National Center for Biotechnology Information database, and only nine ST1791^O/ST2^P isolates were detected. Comparative genomic analysis revealed that ST1791^O/ST2^P carried 11 unique genes, 5 of which were located within the capsular polysaccharide synthesis (cps) gene cluster. Single nucleotide polymorphisms (SNPs) between ST1791^O/ST2^P and other isolates were primarily found in the cps gene cluster. Among the other isolates, ST195^O/ST2^P and ST208^O/ST2^P exhibited the smallest SNP differences from ST1791^O/ST2^P, while ST195^O/ST2^P and ST1486^O/ST2^P had high homology. The ST1791^O/ST2^P strain in Anhui, China, displayed significant homology with ST195^O/ST2^P, ST208^O/ST2^P, and ST1486^O/ST2^P isolates. Compared to other isolates in this study, ST1791^O/ST2^P exhibited strong growth ability and virulence. Therefore, preventing the further spread of ST1791^O/ST2^P should be a top public health priority.