Though Kanamycin and Vancomycin both commonly used antibiotics both of them can not be used in this case as you plasmid is clearly Kan-resistant. Kanamycin interacts with the 30S subunit of prokaryotic ribosomes resulting to substantial amounts of mistranslation and indirectly inhibits translocation during protein synthesis. Vancomycin acts by inhibiting proper cell wall synthesis in gram-+ve bacteria. Due to the different mechanism by which gram--ve bacteria produce their cell walls and the various factors related to entering the outer membrane of gram-negative organisms, vancomycin is not active against gram-negative bacteria except a few species.