Genomic Characterization of Potential Opportunistic Zoonotic Isolated in China.

(1) Background: is a potential opportunistic zoonotic pathogen that can infect pigs, cattle, and humans, composed of former members of serotypes 20, 22, and 26. In recent years, unclassified serotypes and a serotype 11 have been discovered. (2) Methods: We characterized two strains (FZ1 and FZ2) isolated from brain samples of paralyzed pigs and examined evolutionary divergence among 22 available and 8 serotype 2 genomes through whole-genome sequencing and comparative genomic analysis. We compared virulence genes (VGs) and antibiotic resistance genes (ARGs) and analyzed mobile genetic elements (MGEs) in FZ1 and FZ2. (3) Results: Comparative genomics revealed that , , and may represent key virulence determinants in , although their pathogenic potential appears attenuated compared to serotype 2 . In addition, exhibited primary resistance to aminoglycosides, macrolides, tetracyclines, and oxazolidinones, while demonstrating heightened susceptibility to oxazolidinone-class antibiotics. Moreover, we found an important association between MGEs and antibiotic resistance in FZ1 and FZ2. (4) Conclusions: This study provides new insights into the genomic and evolutionary characteristics of and provides a new basis for the study of bacterial pathogenesis and drug resistance in the future.