474Ceftaroline Salvage Therapy for MRSA Bacteremia Following Vancomycin Failure

Background. Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia (MRSAB) is associated with significant morbidity and mortality. Vancomycin (VAN) is the drug of choice for MRSAB, optimization of VAN dosing is challenging in the setting of an elevated MIC (>1-2mcg/ml). Daptomycin (DAP) is an alternative for MRSAB, however DAP MICs tend to be elevated among patients with elevated VAN MICs or that failed VAN, increasing the risk for DAP failure. Ceftaroline (CFT) is active against MRSA and may be considered in the management of MRSAB as well. We summarize our experience with CFT as salvage therapy (ST) for MRSAB and the correlation observed between elevated VANMIC and/or VAN failure and DAP MIC. Methods. All adult patients that received CFT ST for MRSAB following VAN failure and/or in the setting of elevated VAN MIC (>1-2 mcg/ml) between August 31, 2012 to April 30, 2014 were included. Patients were evaluated for clearance and duration of positive blood cultures, MIC data, ST regimen, and VAN duration. MIC methodology included: VAN (Vitek-2); DAP (Etest); CFT (agar dilution). Results. Six MRSAB patients initially treated with VAN received CFT ST. All patients received prior or concomitant DAP with CFT. Five of 6 patients received an additional anti-MRSA antibiotic. Median VAN duration was 9 days and median total duration of positive blood cultures was 8.5 days. 83.3% (N = 5) of patients grew MRSA isolates with a VAN MIC of 1-2 mcg/ml, 3 of these isolates were DAP non-susceptible (NS). An additional MRSA isolate found to be DAP NS occurred in a patient that received 25 days VAN, and was reported to have had an elevated VAN MIC based on outside hospital cultures that could not be confirmed. All isolates were susceptible to CFT (MIC of 0.5-1 mcg/ml). One patient died prior to documented clearance of blood cultures, the remaining 5 survived and cleared blood cultures within 2-3 days following CFT. Conclusion. CFT in combination with an additional agent is effective as ST for MRSAB, resulting in blood culture clearance within 2-3 days. MRSA isolates with elevated VAN MIC values and patients with prolonged courses of VAN exhibited elevated DAP MIC values. CFT may be preferred over DAP for MRSAB following VAN failure and/or an elevated VAN MIC given the prevalence of elevated DAP MICs. Disclosures. J. Pisano, Pfizer: Grant Investigator, Research grant