Activities of the oxazolidinones linezolid and eperezolid in experimental intra-abdominal abscess due to Enterococcus faecalis or vancomycin-resistant Enterococcus faecium

The in vivo effectiveness of oxazolidinones eperezolid (U-100592) and linez olid (U-100766) against one strain each of Enterococcus faecalis and vancom ycin-resistant Enterococcus faecium was examined in a rat model of intraabd ominal abscess. MICs of both drugs were 2 mu g/ml for each strain. At doses of 25 mg/kg of body weight twice daily intravenously or orally, linezolid produced small but statistically significant reductions in abscess bacteria l density for E, faecalis, The reduction in viable cells observed would not likely be clinically relevant. Eperezolid was ineffective at this dose. At a dosage of 100 mg/kg/day, linezolid treatment led to an approximately 100 -fold reduction in viable cells per gram of abscess. Against E faecium infe ctions, intravenous eperezolid and oral linezolid were effective, reducing densities approximately 2 log(10) CFU/g, Both oxazolidinones demonstrated a ctivity against enterococci in this model, However, results were modest wit h the dosing regimens employed.