Multidrug efflux pump that functions probably as a Na(+)/drug antiporter. Confers resistance to the hydrophobic cationic compounds norfloxacin, ethidium bromide and berberine. It provides protection against antibiotics produced by epiphytic bacteria, such as P.agglomerans, which cocolonize plant blossoms. Belongs to the multi antimicrobial extrusion (MATE) (TC 2.A.66.1) family. MdtK subfamily.