The clinical approach to S. aureus bacteremia consists of careful history and physical examination, infectious disease consultation, and diagnostic evaluation including echocardiography and additional imaging as needed.
Patients should be questioned regarding potential portals of entry, presence of indwelling prosthetic devices, and symptoms that may reflect metastatic infection. These include bone or joint pain (particularly back pain, suggesting vertebral osteomyelitis, discitis, and/or epidural abscess) and protracted fever and/or sweats (suggestive of endocarditis).
The physical examination should include cardiac examination for signs of new murmurs or heart failure. A search should be undertaken for clinical stigmata of endocarditis, including evidence of small and large emboli. Serial bedside examinations are critical for detection of complications that may develop after initial evaluation and during the course of treatment.
We recommend bedside infectious disease consultation for management of patients with S. aureus bacteremia (Grade 1B); this is a critical component of management for patients with S. aureus bacteremia and is associated with better outcomes including fewer deaths, fewer relapses, and lower readmission rates.
In general, blood cultures positive for S. aureus should be respected as a clinically significant finding that should prompt clinical evaluation and initiation of empiric therapy. All patients with S. aureus bacteremia should undergo echocardiography to evaluate for presence of endocarditis. Additional diagnostic imaging should be tailored to findings on history and physical examination.
Empiric treatment should consist of antimicrobial therapy with activity against methicillin-resistant S. aureus (MRSA) until culture and susceptibility data are available.
We recommend treating methicillin-sensitive S. aureus (MSSA) bacteremia with a beta-lactam antibiotic (in preference to vancomycin or daptomycin) (Grade 1B). Regimens include penicillin, nafcillin, oxacillin, or flucloxacillin. A first-generation cephalosporin such as cefazolin is an acceptable alternative in patients with hypersensitivity to the preceding agents.
Vancomycin is less effective for treatment of S. aureus bacteremia than beta-lactam agents and should not be administered as primary therapy for methicillin-sensitive strains unless the use of a beta-lactam agent is precluded by drug intolerance.
We recommend NOT combining low-dose aminoglycosides with antistaphylococcal penicillins or vancomycin for treatment of S. aureus bacteremia (Grade 1B).
The duration of therapy depends on the etiology of infection. In general, patients with bacteremia with a removable focus of infection may be treated with 14 days of intravenous therapy from the first negative blood culture.
Once the diagnosis of S. aureus bacteremia has been established and treatment has been initiated, blood cultures should be repeated to document clearance of bacteremia. Failure to clear bacteremia within 48 hours after initiation of therapy should prompt further evaluation, including evaluation of susceptibility data to ensure appropriate antibiotic selection and dosing, as well as clinical evaluation for occult focus of infection that may require drainage or other intervention beyond antimicrobial therapy alone.