Ceftaroline fosamil salvage therapy: an option for reduced-vancomycin-susceptible MRSA bacteraemia

Objectives: To examine the activity of ceftaroline against reduced-vancomycin-susceptible MRSA isolates. Methods: One-hundred and three MRSA blood culture isolates (predominantly ST239-MRSA-III), with varying vancomycin phenotypes, had their ceftaroline MICs determined by broth microdilution and MIC Evaluator strip (Oxoid-Thermo Fisher). Statistical analyses were performed that examined relationships with vancomycin and daptomycin MICs. Mutations in mecA were also examined. Results: All 103 isolates (including 60 heteroresistant vancomycin-intermediate Staphylococcus aureus/vancomycin-intermediate S. aureus) were susceptible to ceftaroline, with one isolate displaying heteroresistance that may be related to a mecA mutation. Higher ceftaroline MICs were associated with vancomycin-susceptible S. aureus isolates. Conclusions: This study highlights that ceftaroline fosamil is an option for salvage therapy based on in vitro activity.