How do you manage a patient with a positive blood culture showing Gram-positive cocci in clusters, likely Staphylococcus aureus (S. aureus), who has already been discharged from the Emergency Department (ED)?

From the Guidelines

Immediate recall of the patient is essential to manage a patient with a positive blood culture showing Gram-positive cocci in clusters likely to be Staphylococcus aureus who has already been discharged from the ED. Contact the patient immediately to return for admission and initiation of intravenous antibiotics, typically vancomycin (15-20 mg/kg IV every 8-12 hours) or daptomycin (6 mg/kg IV daily) while awaiting final identification and susceptibility results, as recommended by 1. For MRSA coverage, vancomycin with target trough levels of 15-20 μg/mL is standard. If the patient cannot return promptly, arrange urgent follow-up at an infusion center or through home health services. A thorough evaluation for source identification is necessary, including:

• Echocardiography to rule out endocarditis, especially with persistent bacteremia, as suggested by 1 and 1
• Blood cultures should be repeated daily until negative to confirm clearance of the infection The typical treatment duration is:
• 14 days for uncomplicated bacteremia
• 4-6 weeks for endocarditis or other complicated infections, as outlined in 1 and 1 S. aureus bacteremia carries a 15-30% mortality risk and significant complication rates, including metastatic infections and endocarditis, making aggressive management crucial even for patients who appear clinically stable, as noted in 1 and 1. Some key points to consider in the management of such patients include:
• The importance of removing any potentially infected catheters or devices, as emphasized by 1 and 1
• The need for close monitoring and follow-up to detect any potential complications early, as suggested by 1 and 1
• The consideration of antibiotic lock therapy for patients with retained catheters, as mentioned in 1 and 1

From the FDA Drug Label

5.9 Persisting or Relapsing S. aureus Bacteremia/Endocarditis Patients with persisting or relapsing S. aureus bacteremia/endocarditis or poor clinical response should have repeat blood cultures. If a blood culture is positive for S aureus, minimum inhibitory concentration (MIC) susceptibility testing of the isolate should be performed using a standardized procedure, and diagnostic evaluation of the patient should be performed to rule out sequestered foci of infection. Appropriate surgical intervention (e.g., debridement, removal of prosthetic devices, valve replacement surgery) and/or consideration of a change in antibacterial regimen may be required.

To manage a patient with a positive blood culture showing Gram-positive cocci in clusters, likely Staphylococcus aureus (S. aureus), who has already been discharged from the Emergency Department (ED), the following steps should be taken:

• Repeat blood cultures should be performed to confirm the presence of S. aureus.
• Minimum inhibitory concentration (MIC) susceptibility testing of the isolate should be performed to guide antibiotic therapy.
• A diagnostic evaluation should be performed to rule out sequestered foci of infection.
• Appropriate surgical intervention and/or consideration of a change in antibacterial regimen may be required. It is essential to carefully evaluate the patient and consider the potential need for re-admission to the hospital for further management 2.

From the Research

Management of Positive Blood Culture for Patient Already Discharged from the ED

• If a patient has already been discharged from the Emergency Department (ED) with a positive blood culture showing Gram-positive cocci in clusters, likely Staphylococcus aureus (S. aureus), the following steps can be taken:
  • Re-contact the patient and arrange for immediate re-evaluation and treatment, as S. aureus bacteremia can lead to severe complications, including endocarditis, septic arthritis, and osteomyelitis 3
  • Obtain antibiotic susceptibility results to guide appropriate therapy, as S. aureus can be methicillin-susceptible (MSSA) or methicillin-resistant (MRSA) 4, 3
  • Consider empirical antibiotic treatment with vancomycin or daptomycin, which are active against MRSA, until susceptibility results are available 3
  • Once S. aureus susceptibilities are known, MSSA should be treated with cefazolin or an antistaphylococcal penicillin, while MRSA should be treated with vancomycin, daptomycin, or ceftobiprole 3

Diagnostic Considerations

• The use of rapid diagnostic assays, such as the Xpert MRSA/SA BC system, can help identify S. aureus and its antibiotic susceptibility, allowing for earlier appropriate treatment and reduced unnecessary antistaphylococcal treatment 4
• Other rapid methods, such as API RAPIDEC staph, tube coagulase test, and peptide nucleic acid fluorescence in situ hybridization, can also be used for direct identification of S. aureus from positive blood cultures 5

Treatment and Outcome

• 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 3, 6
• Monitoring of the time to positive blood culture can be helpful in the early recognition of treatment failure, as a lack of increase in time to blood culture positivity in a patient with persistent MRSA bacteremia predicts failure of antimicrobial therapy 7