Efficacy of linezolid against Staphylococcus aureus in different rodent skin and soft tissue infections models

Linezolid is approved for complicated and uncomplicated skin and soft tissue infections. We have evaluated the efficacy of this drug in murine as well as in rat skin and soft tissue infection models using Staphylococcus aureus ATCC and clinical strains. In thigh infection model the dose of linezolid required for more than 1 log 10 kill from baseline inoculum in neutropenic mice and rats was 100 mg/kg and 50 mg/Kg BW bid /day, respectively, which was 5 and 4 folds more than that in immunocompetent animals, respectively. Dose required to achieve 1 log 10 killing was similar against different strains of S. aureus in immunocompetent mouse thigh infection model. However, in murine groin abscess infection model, a dose of 100 mg/kg, b.i.d/day of linezolid produce static effect in 2 days, but revealed to be superior in 4 days treatment and showed approximately 1 log 10 killing from base line inoculums. Based upon pharmacokinetic profile, a 24-h AUC/MIC required for linezolid efficacy in murine groin abscess model was 91.5 for the strain used in this study. As linezolid is taken as a gold standard drug in the evaluation of new chemical entity, this data could be useful for comparing the preclinical efficacy of new anti-MRSA agents.