Comparative Genomics of Two Newly Sequenced Rodent-Derived and One Previously Reported Tick-Derived Borrelia garinii Strains from South Korea Reveals Plasmid Variation and Virulence Gene Diversity.

Borrelia garinii is a spirochete associated with Lyme borreliosis and is widely distributed across Eurasia. Although its genomic features have been well characterized in Europe, genomic data from East Asian isolates remain limited. Two B. garinii strains, HN13 and HN18, were isolated from a wild rodent (Apodemus agrarius) in South Korea and subjected to whole-genome sequencing and comparative genomic analysis. Their genomic features were compared with those of a tick-derived Korean strain 935 and additional global reference genomes. Phylogenetic analyses revealed that B. garinii strain HN18 clustered closely with French strains CIP103362 and 20047, whereas B. garinii strain HN13 showed high chromosomal similarity to the Korean strain 935. Both rodent-derived strains harbored plasmids carrying virulence-associated genes, including vlsE and vls silent cassettes, which were absent in B. garinii strain 935. This study provides new genomic insights into B. garinii circulating in East Asia and reveals host-associated plasmid variation linked to virulent potential. This study also suggests possible trans-Eurasian gene flow and underscores the need for continued genomic surveillance to better understand the evolution and epidemiology of Borrelia species.