Multidrug-Resistant Enterococcus faecium Endocarditis Treated with Combination Tigecycline and High-Dose Daptomycin

OBJECTIVE: To report a case of multidrug-resistant Enterococcus faecium requiring combination antibacterial therapy. CASE SUMMARY: A 39-year-old female presented with chest pain and a history of endocarditis 3 years prior to admission. Blood cultures were positive for E. faecium. She was treated initially with daptomycin 6 mg/kg daily, which was later increased to 8 mg/kg daily despite poor gentamicin clearance. A variety of antibiotics were used in combination with daptomycin, but the patient remained febrile, with positive blood cultures revealing vancomycin minimum inhibitory concentration (MIC) greater than 256 mu g/mL and daptomycin MIC 3 mu g/mL (and later, 4 mu g/mL). Following the addition of tigecycline, the patient experienced rapid clinical and microbiologic improvement, and blood cultures remained negative 9 weeks after discharge. DISCUSSION: Limited clinical data support the use of daptomycin for the treatment of E faecium endocarditis, and information regarding the effects of escalating doses and combination therapy is scant. After failing multiple combination regimens, this patient responded to a combination of tigecycline and daptomycin. Daptomycin 8 mg/kg daily did not result in creatine kinase elevation in the face of evidence of possible renal dysfunction. CONCLUSIONS: Increasing doses of daptomycin may enhance efficacy without compromising safety, even in patients with some renal dysfunction. The combination of daptomycin and tigecycline may be useful for the treatment of multidrug-resistant E. faecium.