Hospitalized patients at least 18 years of age, with Staphylococcus aureus bacteremia (SAB) will be enrolled into the study and receive one dose of Aurexis® intravenously on Study Day 1, and will be followed until Study Day 57. Aurexis is a humanized monoclonal antibody that is designed to combat Staphylococcus aureus.

The purpose of this study is to assess the safety and pharmacokinetics of standard antibiotic therapy, plus Aurexis or Placebo for treatment of (SAB). Additionally, certain tests and measurements will be conducted to preliminarily determine if Aurexis demonstrates any benefit to these patients.

Inclusion Criteria:

• Male or female, age ≥ 18 years old
• Informed consent obtained from subject or legal guardian
• Willing to practice reliable birth control measures during the study period
• Diagnosis of SAB, as evidenced by clinical symptoms and one positive blood culture obtained ≤ 72 hours prior to initiation of study drug infusion

Exclusion Criteria:

• Pregnant or nursing females
• Polymicrobial bacteremia
• Diagnosis of septic shock (refer to APPENDIX B)
• Neutropenia (absolute neutrophil count < 500/mm³)
• Undergoing any type of dialysis or expected to start dialysis within 30 days
• Moribund clinical condition with a high likelihood of death within 72 hours of randomization
• Received an investigational drug within 30 days of study entry
• Considered unlikely to comply with the study procedures or to return for scheduled post-treatment evaluations