Evolution of multidrug-resistant IncC plasmids in the seventh pandemic Vibrio cholerae O1 El Tor lineage between 1979 and 2024

IncC plasmids played an important role in antimicrobial resistance development in the seventh pandemic Vibrio cholerae O1 El Tor (7PET) lineage during the 1970s and have recently begun to re-emerge. We investigated 28 complete IncC plasmids, including 17 newly sequenced genomes, from 7PET isolates collected across Asia, Africa, and the Caribbean between 1979 and 2024 and spanning the global 7PET phylogeny. Four additional IncC plasmids from other species were included, for a total of 32 IncC plasmids. IncC type 2 predominated among V. cholerae plasmids, and five novel core genome sequence types (cgSTs) were identified. Antimicrobial resistance genes (ARGs) occurred within diverse genetic structures inserted at specific sites in the conserved IncC backbone. Despite remarkable diversity in ARGs and associated genomic islands, the IncC backbone remained stable over five decades. These findings highlight the dynamic evolution and adaptability of IncC plasmids in 7PET under antimicrobial selection.