COMPARATIVE IN-VITRO AND IN-VIVO EFFICACY OF ROXITHROMYCIN AND ERYTHROMYCIN AGAINST A STRAIN OF METHICILLIN-SUSCEPTIBLE STAPHYLOCOCCUS-EPIDERMIDIS

The in vitro and in vivo efficacy of roxithromycin was compared with t hat of erythromycin, against a methicillin-susceptible strain of Staph ylococcus epidermidis. We performed standard in vitro testing (MIC, MB C, and time-kill kinetics) for roxithromycin, erythromycin, and rifamp in. Both macrolides were bacteriostatic in vitro. There was no signifi cant difference in microbial survival between erythromycin and roxithr omycin groups in the time-kill kinetics (p = 0.3). For the in vivo exp eriments, using the rabbit experimental endocarditis model, roxithromy cin was found to be inferior to erythromycin in decreasing the microbi al burden of the endocardial vegetations (p < 0.05). Rifampin was high ly effective, both in vitro and in vivo. In conclusion, the efficacy o f roxithromycin was poor and inferior to erythromycin against a strain of methicillin-susceptible S. epidermidis. (C) 1998 Elsevier Science Inc.