Multidrug-resistant bacteria and pan-drug resistant bacteria are major clinical concerns associated with misuse and abuse of antibiotics. The multidrug efflux pumps and biofilm formation, two mechanisms of drug resistance, are catching more attentions recently. Studies demonstrated that some efflux pumps in different bacteria influence biofilm formation, which in turn changes the gene expression of efflux pumps, indicating a possible interaction between multidrug efflux pumps and biofilm formation.