POTENTIAL OF CLINDAMYCIN IN ADDITION TO VANCOMYCIN FOR THE TREATMENT OF OXACILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS SEPTICEMIA PERSISTING UNDER VANCOMYCIN THERAPY

We observed seven patients with persistent fever and staphylococcemia under vancomycin-containing antimicrobial regimens who promptly improv ed as clindamycin was added to the initial antibiotics. Moreover, in a ll these patients a striking increase in peak and trough serum inhibit ory activity (SIR) and serum bactericidal activity (SBA) levels was ob served after addition of clindamycin. SIA and SEA levels after adminis tration of a single dose of vancomycin (500 mg), clindamycin (600 mg) or vancomycin + clindamycin were also measured in three healthy volunt eers against six ORSA isolates. Unsatisfactory peak SEA levels (0% of cases greater than or equal to 1:8) were obtained after vancomycin adm inistration. Vice versa, peak SEA levels greater than or equal to 1:8 were obtained in 94% of the cases after clindamycin and in 100% of cas es after vancomycin + clindamycin. Time-kill studies showed a borderli ne or incomplete bactericidal activity of vancomycin against three ORS A isolates from infections that manifested poor or slow response to va ncomycin therapy. The combination with clindamycin did not result in a synergistic interaction between the two drugs. It is concluded that a ddition of clindamycin may be useful in some cases of ORSA septicemia that show poor or slow response to vancomycin therapy. The recommendat ion for a wider use of this combination of antibiotics requires furthe r documentation of efficacy.