Methicillin-Resistant Staphylococcus aureus Endovascular Infection in a Neonate: Prolonged, Safe, and Effective Use of Daptomycin and Enoxaparin.

We report on a former 28-week gestation neonate with persistent methicillin-resistant Staphylococcus aureus (MRSA) endocarditis, with a heterozygous Factor V Leiden mutation. The neonate became clinically ill after 1 week of life, with positive blood cultures for MRSA. Echocardiography revealed large thrombi in the inferior vena cava and right atrium. Bacteremia persisted despite removal of umbilical arterial and venous catheters and empiric administration of therapeutic doses of vancomycin (minimum inhibitory concentration [MIC] 2 mg/L) and ceftazidime. To narrow therapy, ceftazidime was discontinued, while gentamicin and rifampin were added. Cultures remained positive and, therefore, linezolid was added, and subsequent blood cultures became negative. Since prolonged linezolid use of 2 weeks or longer carries potential adverse effects, antibiotics were changed to daptomycin, which is bactericidal and recommended for treatment of invasive MRSA infections when vancomycin MICs are ≥2 mg/L to minimize vancomycin treatment failure. Enoxaparin was initiated, with anti-Xa assay monitoring. A workup for thrombophilia revealed heterozygous Factor V Leiden mutation. Serial echocardiograms demonstrated decreasing size of the thrombi, which were no longer visualized at 2 months of age. Creatinine kinase remained normal. The infant had no seizures on daptomycin. The management of persistent MRSA bacteremia in neonates associated with a large thrombus poses a unique challenge due to the long duration of treatment. To our knowledge, this is the first case of prolonged and safe daptomycin and enoxaparin use in a preterm neonate. Daptomycin may be considered in cases of clinical failure with vancomycin when a lengthy treatment course is contemplated.