In vitro and in vivo activity of daptomycin plus ceftaroline for the treatment of experimental endocarditis due to Enterococcus faecalis with and without high-level aminoglycoside resistance.

OBJECTIVES

Effective alternatives to standard of care treatment for E. faecalis infective endocarditis (EFIE) are needed. Some in vitro studies have suggested daptomycin and ceftaroline have synergistic activity against E. faecalis. We aimed to assess the in vitro and in vivo activity of daptomycin in combination with ceftaroline against E. faecalis clinical isolates with and without high-level of aminoglycoside resistance (HLAR).

MATERIALS AND

METHODS

A panel of six endocarditis-associated E. faecalis isolates were used for time-kill assays at initial standard and high inocula. Daptomycin (10 mg/kg/day intravenously) and daptomycin (10 mg/kg/day iv) plus ceftaroline (600 mg q12 hours intravenous) were compared in vivo using a human-like pharmacokinetic model in two treatment groups using the experimental EFIE model in rabbits.

RESULTS

The combination of daptomycin plus ceftaroline achieved synergy against all three HLAR and all three non-HLAR strains in time-kill assays at initial standard inoculum. A bactericidal effect was observed in two of the three HLAR E. faecalis isolates. For HLAR EFAE-188, the use of daptomycin plus ceftaroline significantly decreased the bacterial density in vegetations compared with daptomycin alone (median density 5.2 versus 6.7 log10 cfu/g; P = 0.028). For non-HLAR EFAE-468, the bacterial density in vegetations was lower with the combination therapy than with daptomycin alone (median density 5.2 versus 6.8 log10 cfu/g; P = 0.072). Adding ceftaroline prevented the development of daptomycin-resistant E. faecalis isolates in all cases.

CONCLUSIONS

Daptomycin plus ceftaroline represents a promising alternative for treating EFIE. Further clinical studies are needed to confirm these findings.