Mdt(A), a new efflux protein conferring multiple antibiotic resistance in Lactococcus lactis and Escherichia colii

The mdt(A) gene, previously designated mef214, from Lactococcus lactis subs p, lactis plasmid pK214 encodes a protein [Mdt(A) (multiple drug transporte r)] with 12 putative transmembrane segments (TMS) that contain typical moti fs conserved among the efflux proteins of the major facilitator superfamily , However, it also has two C-motifs (conserved in the fifth TMS of the anti porters) and a putative ATP-binding site. Expression of the cloned mdt(A) g ene decreased susceptibility to macrolides, lincosamides, streptogramins, a nd tetracyclines in L. lactis and Escherichia coli, but not in Enterococcus faecalis or in Staphylococcus aureus, Glucose-dependent efflux of erythrom ycin and tetracycline was demonstrated in L. lactis and in E. coli.