Activities of the Oxazolidinones Linezolid and Eperezolid in Experimental Intra-Abdominal Abscess Due to Enterococcus faecalis or Vancomycin-Resistant Enterococcus faecium

Abstract

ABSTRACT The in vivo effectiveness of oxazolidinones eperezolid (U-100592) and linezolid (U-100766) against one strain each of Enterococcus faecalis and vancomycin-resistant Enterococcus faecium was examined in a rat model of intra-abdominal abscess. MICs of both drugs were 2 μg/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 bacterial 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 infections, intravenous eperezolid and oral linezolid were effective, reducing densities approximately 2 log 10 CFU/g. Both oxazolidinones demonstrated activity against enterococci in this model. However, results were modest with the dosing regimens employed.