What is the recommended treatment for Staphylococcus hominis bacteremia?

Treatment of Staphylococcus hominis Bacteremia

For Staphylococcus hominis bacteremia, intravenous vancomycin is the recommended first-line treatment, with daptomycin as an effective alternative. While specific guidelines for S. hominis bacteremia are limited, treatment follows principles established for coagulase-negative staphylococcal and S. aureus bacteremia.

Initial Assessment and Treatment Algorithm

1. Source identification and control:

   • Identify and remove potential sources (especially intravascular catheters)
   • Perform additional blood cultures 2-4 days after initial positive cultures to document clearance 1
   • Obtain echocardiography to rule out endocarditis (TEE preferred over TTE in adults) 1

2. Antimicrobial therapy:

   • First-line: IV vancomycin (15-20 mg/kg/dose every 8-12 hours, with dose adjustments based on AUC monitoring) 1
   • Alternative: Daptomycin 6 mg/kg IV once daily (some experts recommend 8-10 mg/kg/dose for complicated cases) 1

3. Duration of therapy:

   • Uncomplicated bacteremia: Minimum 2 weeks 1
   • Complicated bacteremia: 4-6 weeks 1
   • With endocarditis: 6 weeks 1

Defining Uncomplicated vs. Complicated Bacteremia

Uncomplicated bacteremia requires all of the following 1:

• Exclusion of endocarditis
• No implanted prostheses
• Follow-up blood cultures negative at 2-4 days
• Defervescence within 72 hours of starting effective therapy
• No evidence of metastatic infection

Complicated bacteremia is defined as not meeting all criteria for uncomplicated bacteremia.

Special Considerations

1. Antibiotic resistance patterns:

   • S. hominis strains are frequently multidrug-resistant 2
   • Many S. hominis strains carry the mecA gene (methicillin resistance) 2
   • All strains in recent studies remained sensitive to vancomycin, though some showed reduced sensitivity 2

2. Combination therapy:

   • For refractory cases, combination therapy may be necessary 3
   • Addition of gentamicin or rifampin to vancomycin is NOT recommended for uncomplicated bacteremia or native valve endocarditis 1

3. Monitoring therapy:

   • For vancomycin, use AUC-guided dosing rather than trough-only monitoring 1
   • Target AUC/MIC ratio ≥400 for serious infections
   • Monitor renal function regularly

4. Immunocompromised patients:

   • May require more aggressive and prolonged therapy 3
   • Consider combination therapy for persistent bacteremia 3

Common Pitfalls and Caveats

1. Failure to identify and remove the source (particularly intravascular catheters) is associated with higher relapse and mortality rates 1

2. Inadequate duration of therapy can lead to treatment failure and recurrence

3. Failure to obtain follow-up blood cultures to document clearance of bacteremia

4. Overlooking endocarditis - echocardiography should be performed in all adult patients with bacteremia 1

5. Heterogeneous vancomycin resistance has been reported in some S. hominis strains, which may require higher doses or alternative agents 2

While S. hominis is generally less virulent than S. aureus, its increasing antibiotic resistance and ability to cause persistent bacteremia, especially in immunocompromised patients, warrant careful attention to treatment selection and duration.