729Activity of Ceftaroline and Comparator Agents Tested against Staphylococcus aureus from Patients with Bacteremia in United States (USA) Medical Centers (2009-2013)

Background. Ceftaroline (CPT), the active metabolite of the prodrug CPT fosamil, is the first cephalosporin with potent activity against methicillin-susceptible (MSSA) and -resistant S. aureus(MRSA). CPT is approved for treatment of community-acquired penumonia and acute bacterial skin infections. Methods. 4,426 S. aureusisolates from the AWARE CPT surveillance program were derived from patients with bacteremia in 2009-2013. Isolates were collected in 150 medical centers distributed through all 9 USA Census regions, and tested for susceptibility (S) against CPT and comparators by the CLSI broth microdilution method. S interpretations were determined per CLSI criteria. Results. 45.5% of isolates were MRSA. CPT (MIC50/90, 0.25/1 μg/mL) inhibited 97.9 and 100.0% of S. aureus at ≤1 and ≤2 μg/mL, respectively (Table). Daptomycin (DAP; MIC50/90, 0.25/0.5 μg/mL), linezolid (LZD; MIC50/90, 1/2 μg/mL) and vancomycin (VAN; MIC50/90, 1/1 μg/mL) were active against ≥99.8% of isolates. S rates for erythromycin (MIC50/90, >16/ > 16 μg/mL), clindamycin (CLI; MIC50/ 90, ≤0.25/ > 2 μg/mL) and levofloxacin (LEV; MIC50/90, ≤0.5/ > 4 μg/mL) were 42.5, 80.8 and 59.2%, respectively. Against MSSA, CPT (MIC50/90, 0.25/0.25 μg/ mL; 100.0% S) was 16-, 4and 4-fold more active than ceftriaxone (MIC50/90, 4/ 4 μg/mL), LZD (MIC50/90, 1/2 μg/mL ) and VAN (MIC50/90, 1/1 μg/mL), respectively, and slightly more potent than DAP (MIC50/90, 0.25/0.5 μg/mL). Among MRSA, 95.4 and 100.0% of strains were inhibited at ≤1 and ≤2 μg/mL of CPT, respectively. 35.8% and 75.4% of MRSA were resistant to CLI and LEV, respectively. 99.7% of MRSA strains were DAP-S (MIC50/90, 0.25/0.5 μg/mL), and LZD (MIC50/90, 1/2 μg/mL) and VAN (MIC50/90, 1/1 μg/mL) were active against >99.9% of MRSA strains.