Ceftaroline activity against bacterial organisms isolated from acute bacterial skin and skin structure infections in United States medical centers (2009-2011)

Ceftaroline, the active metabolite of the prodrug ceftaroline fosamil, is a new cephalosporin with bactericidal activity against resistant Gram-positive organisms including methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant strains of Streptococcus pneumoniae, and commonly isolated Gram-negative organisms, including ceftriaxone-susceptible Enterobacteriaceae. We evaluated the in vitro activity of ceftaroline and selected comparator agents against bacterial isolates collected from patients with acute bacterial skin and skin structure infections (ABSSSIs) in the USA. A total of 6222 isolates were collected from 67 medical centers distributed across all nine USA census regions between 2009 and 2011 and tested for susceptibility by reference broth microdilution methods. Ceftaroline was very active against S. aureus (MIC50/90, 0.5/1 μg/mL; 99.6% susceptible), including MRSA (MIC50/90, 0.5/1 μg/mL; 99.1% susceptible). Against β-hemolytic streptococci, the activity of ceftaroline (MIC50/90, ≤0.015/0.03 μg/mL; 100.0% susceptible) was comparable to that of both penicillin (MIC50/90, ≤0.06/≤0.06 μg/mL; 100.0% susceptible) and ceftriaxone (MIC50/90, ≤0.25/≤0.25 μg/mL; 100.0% susceptible). Ceftaroline was also highly active against viridans group streptococci (MIC50/90, 0.03/0.06 μg/mL). Similar to ceftriaxone and ceftazidime, ceftaroline was active against wild-type strains of Escherichia coli (MIC50/90, 0.12/0.25 μg/mL; 94.0% susceptible) and Klebsiella pneumoniae (MIC50/90, 0.12/0.25 μg/mL; 96.8% susceptible); however, the ceftaroline activity was compromised among strains with an extended-spectrum β-lactamase-phenotype (MIC50/90, >32/>32 μg/mL for both E. coli and K. pneumoniae). In summary, ceftaroline showed potent activity against a large contemporary collection (6222) of bacterial isolates associated with ABSSSI in the USA.