In vitro activity of RBx 7644 (ranbezolid) on biofilm producing bacteria.

Biofilm associated infections are becoming more common. Treatment outcome of device related infections cannot be predicted by the results of a standard susceptibility test such as the MIC. Microorganisms involved in device related infections have a slow growth rate and adhere to surfaces. Activity against glass adherent bacteria has been shown to be correlated with treatment outcome in animal models of catheter related infections. Drug efficacy can be predicted if glass adherent staphylococci are killed by low drug concentration. The eradication of bacteria adhering to glass beads and inhibition of biofilm formation by ranbezolid and three other antibiotics (quinupristin/dalfopristin, vancomycin and linezolid) was studied. The results indicated that ranbezolid required only (2-4 x MIC) for total clearance of glass-adherent MRSA 562 and MRSE 879, compared with vancomycin (8 x), quinupristin/dalfopristin (1-4 x) and linezolid (4-16 x MIC). In addition ranbezolid inhibited biofilm formation to a greater extent at sub MIC and MIC level. In conclusion, this study indicated that ranbezolid had potent activity against adherent staphylococci isolates and may prove useful in the prevention and treatment of device related infections caused by staphylococci.