Daptomycin compared with teicoplanin and vancomycin for therapy of experimental Staphylococcus aureus endocarditis

The efficacies of daptomycin, teicoplanin, and vancomycin were compared in the therapy of experimental Staphylococcus aureus endocarditis. Rabbits infected with either of two methicillin-susceptible strains (SA-12871 or its moderately teicoplanin-resistant derivative SA-12873) or a methicillin-resistant S. aureus strain (MRSA-494) were treated with daptomycin, 8 mg/kg of body weight, every 8 h; teicoplanin, 12.5 mg/kg (low-dose teicoplanin [teicoplanin-LD], excluding MRSA-494) or 40 mg/kg (high-dose teicoplanin [teicoplanin-HD]) every 12 h; or vancomycin, 17.5 mg/kg every 6 h, for 4 days. Compared with no treatment daptomycin, teicoplamin-HD, and vancomycin significantly reduced bacterial counts of all test strains in vegetations and renal and splenic tissues (P less than 0.001). Teicoplanin-LD was equally effective against SA-12871 but failed against SA-12873, with three of six animals still being bacteremic at the end of therapy. For SA-12871, daptomycin was as effective as teicoplanin-HD and was superior to teicoplanin-LD and vancomycin (P = 0.02) in lowering vegetation bacterial counts. There were no differences between daptomycin, teicoplanin-HD, or vancomycin in the reduction of bacterial counts in tissues for any of the test strains. In rabbits infected with SA-12871, vegetations from 33% of teicoplanin-LD-treated, 6% of teicoplanin-HD-treated, and 13% of daptomycin-treated animals yielded organisms for which there were up to eightfold increases in the MICs. Resistance may have contributed to early death in one daptomycin-treated animal. No increases in the MICs for the test strain were detected in animals infected with SA-12873 or MRSA-494. We conclude that in this model and against these strains of S. aureus, daptomycin and teicoplanin-HD are as efficacious as vancomycin, but diminished susceptibility to both can develop during therapy.