What to do if Enterococcus faecalis (E. faecalis) colony-forming units (CFU) are greater than 100 three days after starting antibiotic treatment?

Management of Enterococcus faecalis with >100 CFU Three Days After Antibiotic Treatment

For persistent Enterococcus faecalis infection with colony counts >100 CFU after three days of antibiotic therapy, the most appropriate action is to reassess antibiotic selection and consider changing to ampicillin for ampicillin-susceptible strains or vancomycin for resistant strains, while removing any infected catheters if present. 1

Evaluation of Persistent Infection

When E. faecalis persists after initial antibiotic therapy, consider the following factors:

1. Source of infection:

   • Determine if there is a catheter-related infection
   • Check for endocarditis, especially with persistent bacteremia
   • Evaluate for undrained abscesses or other foci of infection

2. Current antibiotic regimen:

   • Verify appropriate antibiotic selection based on susceptibility
   • Assess dosing adequacy
   • Check for potential drug interactions reducing efficacy

3. Antimicrobial susceptibility:

   • Review susceptibility testing results
   • Consider high-level aminoglycoside resistance (HLAR) if combination therapy was used

Treatment Recommendations

For Catheter-Related Infections:

• Remove infected catheters if present, particularly with:

  • Insertion site/pocket infection
  • Suppurative thrombophlebitis
  • Persistent bacteremia
  • Sepsis or metastatic infection 1

• Antibiotic selection:

  • Ampicillin is the drug of choice for ampicillin-susceptible enterococci
  • Vancomycin should be used if the pathogen is resistant to ampicillin 1
  • For ampicillin and vancomycin-resistant enterococci, consider linezolid or daptomycin based on susceptibility results 1, 2

• Treatment duration:

  • 7-14 days for uncomplicated enterococcal infections where the catheter is removed 1
  • Longer duration (up to 4-6 weeks) for complicated infections like endocarditis 1

For Endocarditis Consideration:

• Perform transesophageal echocardiography (TEE) if the patient has:

  • Signs/symptoms suggesting endocarditis (new murmur, embolic phenomena)
  • Prolonged bacteremia or fever (>72 hours after appropriate therapy)
  • Radiographic evidence of septic pulmonary emboli
  • Prosthetic valve or other endovascular foreign bodies 1

• Antibiotic regimens for endocarditis:

  • Ampicillin plus ceftriaxone is recommended for E. faecalis endocarditis 1
  • For aminoglycoside-resistant strains, double β-lactam therapy is reasonable 1

Follow-up Recommendations

• Repeat blood cultures to document clearance of bacteremia
• Remove catheter if persistent bacteremia (>72 hours after appropriate therapy) is detected 1
• Consider antibiotic lock therapy in addition to systemic therapy if long-term catheter must be retained 1

Common Pitfalls to Avoid

1. Using ineffective antibiotics:

   • Avoid cephalosporin monotherapy, as E. faecalis is intrinsically resistant 3
   • Don't use clindamycin or trimethoprim-sulfamethoxazole as monotherapy 3

2. Inadequate source control:

   • Failure to remove infected catheters or drain abscesses
   • Overlooking potential endocarditis

3. Insufficient treatment duration:

   • While 7 days may be sufficient for uncomplicated catheter-related infections 4, more complex infections require longer treatment

4. Missing synergistic resistance:

   • Failing to identify high-level aminoglycoside resistance when using combination therapy

Special Considerations

• For patients requiring outpatient parenteral antimicrobial therapy for E. faecalis endocarditis, combination regimens of ampicillin plus ceftriaxone have been successfully used 5, 6
• In pediatric patients with recurrent urinary tract infections, E. faecalis may persist despite prophylaxis, and alternative approaches may be needed 7

By following these guidelines and addressing the specific factors contributing to persistent E. faecalis infection, you can optimize treatment outcomes and reduce the risk of complications.