A combination of roxithromycin and imipenem as an antimicrobial strategy against biofilms formed by Staphylococcus aureus

We examined the effects of a combination of roxithromycin and imipenem on a biofilm model of Staphylococcus aureus. Treatment with roxithromycin alone and imipenem alone did not decrease the number of viable bacterial cells compared with the control. However, a combination treatment of roxithromycin and imipenem significantly decreased the number of viable bacterial cells on day 8 after inoculation in the in vivo model (P < 0.01). On days 5 and 8 after inoculation, numerous polymorphonuclear leucocytes and macrophages invaded the bacterial clusters in the roxithromycin- and roxithromycin/imipenem-treated groups, but did not invade the control or imipenem-treated groups. The present study indicated that a combination of roxithromycin and imipenem is a potentially effective treatment for S. aureus biofilm-associated skin infections as it can induce the invasion of polymorphonuclear leucocytes into the biofilm.