Comparative in vitro activity of the new oxazolidinones DuP 721 and DuP 105 against staphylococci and streptococci.

The in vitro activity of DuP 721 and DuP 105, two orally active members of the oxazolidinones, was compared with that of glycopeptides and ciprofloxacin against 185 gram-positive isolates. Ninety percent of Staphylococcus aureus isolates, including penicillin- and methicillin-resistant strains, were inhibited by DuP 721 at 1 micrograms/ml and by DuP 105 at 16 micrograms/ml; DuP 721 inhibited 90% of coagulase-negative staphylococci tested at 1 micrograms/ml. The MIC90 for Streptococcus faecalis was 4 micrograms/ml with DuP 721 and 16 micrograms/ml with DuP 105; DuP 721 inhibited 90% of beta-hemolytic streptococci of group A at 0.5 micrograms/ml. Similar results on selected strains were obtained by continuously recording the optical density of cultures.