A newly identified sequence type: genomic and pathogenic profiling of the highly virulent Acinetobacter baumannii ST3475 from bovine mastitis

Background: involved in bovine mastitis in China remain poorly understood, particularly with emergence of novel sequence types. Methods: infection models). Results: = 1,378,077 CFU/larva). In a murine mammary infection model, ST3475 caused substantial alveolar destruction and inflammatory infiltration. Conclusion: Phylogenetically, ST3475 belongs to clonal complex CC2 but represents a distinct, putative bovine-adapted lineage separate from major human clone CC1. Although currently susceptible to last-resort antimicrobials like carbapenems, carriage of high-risk resistance genes highlights livestock as a potential reservoir for clinically relevant resistance determinants. This study reveals ST3475 as a novel, virulent, and putative bovine-adapted lineage, underscoring the importance of One Health surveillance.