In vitro activity of ceftaroline against Spanish isolates of Staphylococcus aureus: a multicenter study

Background: Ceftaroline fosamil is a new-generation antimicrobial agent of cephalosporins subgroup. It is the first commercially available beta-lactam antibiotic that exhibits activity against methicillin-resistant Staphylococcus aureus (MRSA). The aim of this study is to determine the in vitro Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values of ceftaroline against S.aureus strains (including MRSA).

Methods: A multicenter study involving four hospitals representative of the Spanish geography was performed. MIC and MBC values against both the methicillin-resistant and sensitive strains of S.aureus (MRSA and methicillin-sensitive S.aureus [MSSA]) were determined using a broth microdilution method.

Results: A total of 266 S.aureus strains were analyzed (95 MRSA and 171 MSSA). Ceftaroline bacterial sensitivity showed a mean MIC of 0.227 μg/ml (SD=0.146; range, 0.06 to 1 μg/ml). All MIC values of the 266 strains tested belonged to the sensitive category (value ≤ 1 μg/ml). Intermediate or resistant strains were not detected. MIC50 and MIC90 values for MRSA were 0.25 and 0.5 μg/ml, respectively (range=0.125-1 μg/ml). MSSA strains showed MIC50 and MIC90 values of 0.125 and 0.25 μg/ml, respectively (range=0.125-0.5 μg/ml). MBC50 and MBC90 values for MRSA were 0.5 and 1 μg/ml, respectively (range=0.125-1 μg/ml). MSSA strains showed MBC50 and MBC90 values of 0.25 and 0.25 μg/ml, respectively (range=0.125-0.5 μg/ml).

Conclusions: Ceftaroline shows excellent in vitro activity against S.aureus, including MRSA strains. Therefore, this antibiotic may be a promising alternative for the treatment of infections caused by this bacterium.