In-vitro activity of RP 59500, a new semisynthetic injectable pristinamycin against staphylococci.

We compared the in vitro activity of RP 59500, a new streptogramin, with that of vancomycin and ciprofloxacin against 130 strains of S. aureus and 117 strains of coagulase-negative staphylococci, using the agar dilution method. The antistaphylococcal activity of RP 59500 was similar to that of vancomycin. All staphylococcal strains were inhibited by < or = 2 micrograms/mL, including 61 methicillin-resistant S. aureus, 28 methicillin-resistant S. epidermidis and 23 methicillin-resistant S. haemolyticus strains. In contrast to ciprofloxacin, the in vitro activity of RP 59500 as well as of vancomycin remained almost unchanged, irrespective of the resistance phenotype for methicillin.