Comparative efficacy of telavancin and daptomycin in experimental endocarditis due to multi-clonotype MRSA strains

Background MRSA strains of clonal complexes (CCs) 5, 8, 30 and 45 are leading causes of complicated endovascular infections associated with suboptimal clinical outcomes. Telavancin is a novel anti-MRSA agent that both inhibits bacterial cell wall synthesis and disrupts membranes by depolarization. Methods In this study, we compared the in vitro susceptibility and in vivo efficacy of telavancin versus daptomycin in an experimental rabbit infective endocarditis (IE) model caused by four MRSA strains representing each of the above CC types. Results All study strains were susceptible to telavancin (MICs of ≤0.12 mg/L) and daptomycin (MICs of ≤0.5 mg/L). In vitro time–kill analyses revealed that supra-MIC levels of telavancin were effective at preventing regrowth at 24 h of incubation. In the IE animal model for all CC types, treatment with telavancin produced significantly greater reductions in MRSA counts as compared with daptomycin-treated animals in all target tissues. Moreover, telavancin-treated animals had a significantly higher percentage of sterile tissue cultures versus daptomycin-treated animals (e.g. 78%–100% versus 0% sterile vegetations and 100% versus 0%–11% sterile kidneys and spleen, in the telavancin- and daptomycin-treated animals, respectively). Conclusions These results suggest that telavancin exhibits significantly greater efficacies versus daptomycin in treating experimental IE caused by MRSA clinical isolates across four common CC types.