Linezolid and daptomycin are the only 2 antimicrobial agents currently available in the United States that may be useful for the treatment of multidrug-resistant E faecium IE. Quinupristin-dalfopristin may be active in vitro but only against strains of E faecium and is inactive against E faecalis. Quinupristin-dalfopristin is rarely used because of severe side effects, including intractable muscle pain. Tigecycline is active in vitro against some strains of multidrug-resistant enterococci, but there are minimal published data on its use clinically. The same can be said for tedizolid, which has been released. Table 15 lists possible therapeutic options for the treat- ment of multidrug-resistant enterococcal IE. These patients should be managed by specialists in infectious diseases, car- diology, cardiovascular surgery, clinical pharmacy, and, if necessary, pediatrics. Antimicrobial regimens are discussed as follows. Linezolid Linezolid is a synthetic drug that is the first member of the oxazolidinone class. It acts by inhibiting ribosomal protein Table 13. Therapy for Endocarditis Involving a Native or Prosthetic Valve or Other Prosthetic Material Resulting From Enterococcus species Caused by a Strain Susceptible to Penicillin and Resistant to Aminoglycosides or Streptomycin-Susceptible Gentamicin-Resistant in Patients Able to Tolerate -Lactam Therapy* Regimen Dose and Route Duration, wk Strength of Recommendation Comments Double -lactam Ampicillin 2 g IV every 4 h 6 Class IIa; Level of Evidence B Double -lactam is reasonable for patients with normal or impaired renal function abnormal cranial nerve VIII function or if the laboratory is unable to provide rapid results of streptomycin serum concentration; native valve infection with symptoms of infection <3-mo duration may be treated for 4 wk with the streptomycin-containing regimen. PVE, NVE with symptoms >3 mo, or treatment with a double -lactam regimen require a minimum of 6 wk of therapy. 