Management of Staphylococcus aureus Bacteremia

Importance: Staphylococcus aureus, a gram-positive bacterium, is the leading cause of death from bacteremia worldwide, with a case fatality rate of 15% to 30% and an estimated 300 000 deaths per year. Observations: Staphylococcus aureus bacteremia causes metastatic infection in more than one-third of cases, including endocarditis (≈12%), septic arthritis (7%), vertebral osteomyelitis (≈4%), spinal epidural abscess, psoas abscess, splenic abscess, septic pulmonary emboli, and seeding of implantable medical devices. Patients with S aureus bacteremia commonly present with fever or symptoms from metastatic infection, such as pain in the back, joints, abdomen or extremities, and/or change in mental status. Risk factors include intravascular devices such as implantable cardiac devices and dialysis vascular catheters, recent surgical procedures, injection drug use, diabetes, and previous S aureus infection. Staphylococcus aureus bacteremia is detected with blood cultures. Prolonged S aureus bacteremia (≥48 hours) is associated with a 90-day mortality risk of 39%. All patients with S aureus bacteremia should undergo transthoracic echocardiography; transesophageal echocardiography should be performed in patients at high risk for endocarditis, such as those with persistent bacteremia, persistent fever, metastatic infection foci, or implantable cardiac devices. Other imaging modalities, such as computed tomography or magnetic resonance imaging, should be performed based on symptoms and localizing signs of metastatic infection. Staphylococcus aureus is categorized as methicillin-susceptible (MSSA) or methicillin-resistant (MRSA) based on susceptibility to β-lactam antibiotics. Initial treatment for S aureus bacteremia typically includes antibiotics active against MRSA such as vancomycin or daptomycin. Once antibiotic susceptibility results are available, antibiotics should be adjusted. Cefazolin or antistaphylococcal penicillins should be used for MSSA and vancomycin, daptomycin, or ceftobiprole for MRSA. Phase 3 trials for S aureus bacteremia demonstrated noninferiority of daptomycin to standard of care (treatment success, 53/120 [44%] vs 48/115 [42%]) and noninferiority of ceftobiprole to daptomycin (treatment success, 132/189 [70%] vs 136/198 [69%]). Source control is a critical component of treating S aureus bacteremia and may include removal of infected intravascular or implanted devices, drainage of abscesses, and surgical debridement. Conclusions and relevance: Staphylococcus aureus bacteremia has a case fatality rate of 15% to 30% and causes 300 000 deaths per year worldwide. Empirical antibiotic treatment should include vancomycin or daptomycin, which are active against MRSA. Once S aureus susceptibilities are known, MSSA should be treated with cefazolin or an antistaphylococcal penicillin. Additional clinical management consists of identifying sites of metastatic infection and pursuing source control for identified foci of infection.