Comparative Genomic and Phenotypic Characterization of Bloodstream Acinetobacter baumannii Isolates from Children and Adults in Southern China

Acinetobacter baumannii is a major pathogen responsible for hospital-acquired bloodstream infections, with multidrug-resistant (MDR) strains posing severe therapeutic challenges. Neonates are particularly vulnerable to these infections, often associated with high morbidity and mortality. In this study, 77 A. baumannii blood isolates were analyzed by Whole-Genome Sequencing, comparing pediatric (n=42) and adult (n=35) groups. We investigated key antibiotic resistance mechanisms, including beta-lactamases production and multidrug efflux pumps, as well as virulence factors, such as porins, lipopolysaccharides, metal acquisition systems, and virulence secretion systems. Our results revealed a markedly higher imipenem resistance rate in pediatric isolates (97.6%) compared to adults (74.3%), accompanied by a higher prevalence of OXA-66 (OXA-51-like) and OXA-167 (OXA-23-like) carbapenemase genes. Additionally, adult isolates exhibited greater diversity in OXA-type carbapenemases. Virulence factor analysis showed widespread distribution of porins, lipopolysaccharide synthesis genes, metal acquisition systems, and Type VI secretion system components across both groups. Some virulence-related genes demonstrated higher detection rates in pediatric isolates. These insights into resistance patterns and virulence factors are beneficial for timely guidance of empirical medication and infection control strategies against A. baumannii infections.