However, linezolid-resistant strains have devel- oped during treatment.201 In a small number of patients, linezolid was effective ther- apy of vancomycin-resistant E faecium IE.174 Birmingham et reported cure in 17 of 22 courses of therapy (77%) for E faecium IE. Mave et al203 reported cure in 2 of 3 patients with E faecium IE with linezolid. Other case reports of cure of E faecium IE of native valve204 or prosthetic valve205 were reported. However, linezolid treatment failures of E faecium IE also were reported.206 The advantages of linezolid therapy include high bio- availability of the oral formulation, approval for pediatric patients, and a lack of many therapeutic alternatives. The disadvantages are toxicity (mild to severe neutropenia and thrombocytopenia that is reversible); peripheral and optic neuritis, which is more often seen with longer durations of therapy and may not be reversible; multidrug interactions, especially serotonin uptake inhibitors; and emergence of resistance during treatment. The previous high cost should decrease with generic availability soon. Cardiac valve replacement surgery may be necessary in patients who do not respond to linezolid therapy. Daptomycin Daptomycin is a cyclic lipopeptide antibiotic that has bacteri- cidal activity in vitro against susceptible strains of enterococci. Enterococci are considered daptomycin susceptible with MIC <4 g/mL. Although >90% of enterococci are reportedly susceptible in vitro to daptomycin, the emergence of dapto- mycin resistance is an increasing problem.207 Daptomycin is FDA approved for treatment of S aureus infections but not for enterococcal infections. Daptomycin is not approved for use in pediatric patients. The number of published cases of vancomycin-resistant E faecium IE treated with daptomycin is extremely small, so management conclusions are difficult to define, and the success rate has varied among reported cases. 