Staphylococcus aureus is frequently isolated from food-contact surfaces and food processing environments. A feature of S. aureus that favors its survival in these environment is the ability to form biofilms. This study evaluated the capability of multi-drug resistant (MDR) S. aureus strains to form biofilm. Three strains of S. aureus were used: SA-1199B, which ove¬rexpresses the norA gene encoding the NorA efflux protein which extrudes hydrophilic fluoroquinolones and drugs such as DNA-intercalating dyes; strain RN4220 harboring plasmid pUL5054, which carries the gene encoding the MsrA macrolide efflux protein; and strain IS-58, which possesses the TetK tetracycline efflux protein. Biofilm formation was evaluated in Brain Heart Infusion (BHI) broth after incubation of 18-24 hours at 37 °C in polystyrene microtiter plates. Crystal violet was used to stain the biofilm and its quantification was based on the difference between the optical density (OD) measurements of the test and negative control samples (ΔOD570nm). The isolates were classified as strong (4x ODcontrol< OD), moderate (2x ODcontrol<OD ≤ 4x ODcontrol), weak (ODcontrol< OD ≤ 2x ODcontrol) or none (OD ≤ ODcontrol) biofilm-producing. The strain S. aureus ATTCC 25923 was used as positive (strong producer) control. The three tested strains showed capability to form biofilm. S. aureus SA-1199B and S. aureus RN-4220 were classified as strong biofilm-producers (ΔOD570 1.39 and 0.88, respectively), while the strain S. aureus IS-58 as moderate biofilm-producer (ΔOD 0.609). These results alert for the ability of MDR S. aureus strains to form biofilm because in food processing environments these strains can act as chronic source of contamination.