Antibacterial oxazolidinones. In vitro activity of a new analogue, E3709

The oxazolidinone compound E3709, which contains a 4-pyridyl group, was found to be more active in vitro than other members of this series, such as DuP 721. MIC90 for staphylococci(including methicillin-resistant isolates), streptococci (including Enterococcus faecalis), Clostridia, and diphtheroids was less than 0.5 micrograms/ml. Haemophilus influenzae, Moraxella catarrhalis, and Bacteroides fragilis were less susceptible, with an MIC90 between 2 and 8 micrograms/ml. E3709 MICs of Gram-negative species ranged from 100 to greater than 1000 micrograms/ml. At a concentration of 10 micrograms/ml, E3709 was bactericidal for selected Gram-positive species. A postantibiotic effect of 3 hr was observed against staphylococci. Resistance to E3709 was not detected.