RNAIII-inhibiting peptide (RIP) advantageously treats or reduces the risk of biofilm formation on implanted bone cement, thus reducing the possibility of sustained chemotherapy, hospitalization, or surgical removal of the bone cement. Avoiding sustained chemotherapy reduces the risk of inducing antibiotic resistance. Accordingly, RIP can be used with antibiotics that otherwise would be reserved as a last resort, such as vancomycin. RIP potentiates the activity of vancomycin, minimizing the risk of inducing vancomycin-resistance. The present invention thus is expected to prolong significantly the effectiveness of antibiotics of last resort for the treatment of periprosthetic infection.