Should a patient with previously positive blood cultures for cellulitis, now asymptomatic, return to the ER for repeat blood cultures 4 weeks after initial treatment?

Management of Asymptomatic Patient with Previously Positive Blood Cultures

Repeat blood cultures are not indicated for an asymptomatic patient who had positive blood cultures for cellulitis 4 weeks ago and has completed appropriate treatment. 1

Rationale for Not Repeating Blood Cultures

Guidelines for Cellulitis Blood Cultures

• The European Society of Clinical Microbiology and Infectious Diseases (ESCMID) specifically recommends against routinely obtaining blood cultures in patients presenting with cellulitis/erysipelas 1
• Blood cultures are only recommended in specific circumstances for cellulitis:
  • Immunocompromised patients
  • Patients with high risk of non-standard pathogens
  • Patients with intravascular prostheses, pacemakers, or valvular prostheses 1

Test of Cure Blood Cultures

• Surveillance blood cultures are only recommended in specific scenarios:
  • When a catheter has been retained after catheter-related bloodstream infection 1
  • For persistent bacteremia (lasting >72 hours) 1
  • For endocarditis or suppurative thrombophlebitis 1
  • For S. aureus bacteremia requiring monitoring for clearance 2

Clinical Decision Algorithm

1. Assess for symptoms of ongoing/recurrent infection

   • Patient is asymptomatic → No repeat cultures needed
   • If fever, chills, new skin changes, or other signs of infection → Consider evaluation

2. Consider original pathogen and treatment

   • Simple cellulitis that has been adequately treated → No repeat cultures needed
   • S. aureus bacteremia → Would have required longer treatment and follow-up cultures (not applicable here)

3. Evaluate risk factors for complicated infection

   • No endovascular source → Lower risk of persistent bacteremia 3
   • Not S. aureus infection → Lower risk of persistent bacteremia 3
   • No epidural source → Lower risk of persistent bacteremia 3

4. Time since treatment completion

   • 4 weeks post-treatment with no symptoms → Indicates successful treatment
   • Studies show repeat cultures after 48 hours are low yield for most streptococcal and gram-negative bacteremias 3

Important Considerations

• Unnecessary repeat blood cultures account for approximately one-third of all blood cultures with minimal additional yield 4
• False-positive blood cultures can lead to unnecessary treatment, increased hospital stay, and increased costs 5
• For uncomplicated cellulitis, the chance of a false-positive culture is greater than the prevalence of true positive cultures 5

When Repeat Blood Cultures Would Be Indicated

Repeat blood cultures would be indicated if the patient had:

• Persistent fever or clinical deterioration 2
• S. aureus bacteremia (requires follow-up cultures to document clearance) 2
• Endovascular infection or endocarditis 1
• Retained intravascular device 1
• Immunocompromised status 1

Since the patient is asymptomatic 4 weeks after completing treatment for cellulitis, there is no indication for repeat blood cultures, and the patient does not need to return to the ER for this purpose.