What is the next step in managing a patient with methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia and thrombophlebitis due to intravenous (IV) infiltration, who continues to have fevers and arm swelling despite 2 days of cefazolin therapy and a negative computed tomography (CT) scan for abscess?

Management of MSSA Bacteremia with Persistent Fever and Arm Swelling

The next step in managing this patient with MSSA bacteremia and thrombophlebitis who continues to have fevers and arm swelling despite 2 days of cefazolin therapy should be surgical drainage of the fluctuant area in the left upper extremity, as early drainage of purulent material is essential for optimal therapy. 1

Current Situation Assessment

• The patient has methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia secondary to IV infiltration with thrombophlebitis 1
• Despite 2 days of appropriate antibiotic therapy with cefazolin, the patient continues to have:
  • Persistent fevers
  • Left arm swelling and edema
  • Fluctuant area in the left upper extremity 1
• CT scan of the left upper extremity is negative for abscess, but clinical examination suggests a fluctuant collection 1

Recommended Management Approach

1. Source Control - Immediate Priority

• Surgical drainage of the fluctuant area is urgently needed, even though CT is negative for abscess 1
• Early drainage of purulent material is strongly recommended (strong, high evidence) for patients with MSSA infections and fluctuant collections 1
• Persistent bacteremia and fever despite appropriate antibiotics strongly suggests inadequate source control 1

2. Antibiotic Management

• Continue cefazolin as it is the appropriate first-line therapy for MSSA bacteremia 1, 2
• Cefazolin is recommended for definitive therapy of pyomyositis and soft tissue infections caused by MSSA (strong, moderate evidence) 1
• No need to change antibiotics at this point as:
  • Cefazolin has shown similar or even superior efficacy compared to antistaphylococcal penicillins for MSSA infections 1, 3
  • The issue is likely inadequate source control rather than antibiotic failure 1

3. Additional Diagnostic Workup

• Obtain repeat blood cultures to document clearance or persistence of bacteremia 1
• Consider MRI of the left upper extremity if surgical exploration does not reveal a drainable collection, as MRI is more sensitive than CT for detecting soft tissue infections and pyomyositis 1
• Persistent bacteremia should prompt evaluation for endocarditis with echocardiography 1

Rationale for Surgical Intervention

• The IDSA guidelines strongly emphasize that "in most cases of abscess, drainage is critical for optimal therapy" 1
• Clinical signs of fluctuance suggest a drainable collection despite negative CT findings 1
• Persistent fever and swelling on day 2 of appropriate antibiotic therapy indicates inadequate source control 1
• Early source control is a key evidence-based practice in the treatment of S. aureus bacteremia 1

Common Pitfalls to Avoid

• Do not rely solely on imaging to rule out a drainable collection - clinical examination suggesting fluctuance warrants surgical exploration despite negative CT 1
• Avoid premature switching of antibiotics when the issue is inadequate source control 1
• Do not delay surgical intervention in patients with persistent fever and clinical signs of collection 1
• Avoid focusing only on antibiotic therapy without addressing the source of infection 1

Duration of Therapy

• After achieving source control and clearance of bacteremia, antibiotics should be administered intravenously initially 1
• Once the patient is clinically improved, consider transition to oral antibiotics if bacteremia has cleared promptly and there is no evidence of endocarditis or metastatic abscess 1
• Total duration of therapy should be 2-3 weeks for uncomplicated bacteremia with adequate source control 1, 2
• Longer therapy (4-6 weeks) may be needed for complicated bacteremia with high-risk features 1, 2