This is a study of safety and efficacy of ceftaroline fosamil in Subjects with Staphylococcus aureus Bacteremia or with Methicillin-Resistant Staphylococcus aureus (MRSA) Bacteremia persisting after at least 72 hours of vancomycin and/or daptomycin treatment.

Subjects with either S. aureus bacteremia or persistent MRSA bacteremia will be treated with open label ceftaroline fosamil, safety will be monitored and clearance of bacteremia will be evaluated.

Inclusion Criteria:

1. Presence of bacteremia due solely to:

   • S. aureus on at least 1 blood culture within 72 hours of beginning study drug (Cohort A) OR
   • MRSA on a baseline blood culture and on at least 1 additional blood culture after at least 72 hours of vancomycin and/or daptomycin treatment (Cohort B).

2. Male or female ≥ 18 years of age.

3. If female of childbearing potential must be willing to practice sexual abstinence or dual methods of contraception during treatment and for at least 30 days after the last dose of study drug.

4. Expectation of survival for at least 2 months.

Exclusion Criteria:

1. For subjects in Cohort A: previous therapy for more than 48 hours with any parenteral antibiotic with activity against S. aureus within 72 hours of positive blood culture results.
2. For subjects in Cohort B: previous therapy for more than 48 hours with any parenteral antibiotic with activity against MRSA, except vancomycin and/or daptomycin, within 72 hours of positive blood culture results confirming persistence.
3. Previous episode of S. aureus bacteremia within 3 months.
4. Known left-sided endocarditis or prosthetic heart valve.
5. Osteomyelitis or prosthetic joint infection except new onset nonhardware-associated vertebral osteomyelitis.
6. History of any hypersensitivity or allergic reaction to any β-lactam antibacterial agent.
7. Evidence of significant hepatic, hematologic, or immunologic impairment.
8. Pregnant or nursing females.