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

The multidrug-resistant <i>Acinetobacter baumannii</i> 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 <i>A. baumannii</i> 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 <i>Galleria mellonella</i> 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 (<i>cps</i>) 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.