What is the recommended treatment for Staphylococcus hominis bacteremia?

Treatment of Staphylococcus hominis Bacteremia

Start empiric vancomycin immediately at 15-20 mg/kg IV every 8-12 hours (targeting trough 10-15 mg/L) because S. hominis, like most coagulase-negative staphylococci (CoNS), is typically methicillin-resistant in healthcare settings. 1

Initial Empiric Management

• Vancomycin is the first-line empiric agent for S. hominis bacteremia, as the Infectious Diseases Society of America recommends this approach for all CoNS infections due to high rates of methicillin resistance 1
• Administer a loading dose of 25-30 mg/kg (actual body weight) in seriously ill patients with sepsis to achieve rapid therapeutic levels 2
• Target vancomycin trough levels of 10-15 mg/L for most CoNS infections 1

De-escalation Based on Susceptibility Testing

If susceptibility testing confirms methicillin susceptibility, switch immediately to nafcillin 2 g IV every 4 hours or oxacillin, as beta-lactams are superior to vancomycin for susceptible organisms. 1, 3

• First-generation cephalosporins like cefazolin are acceptable alternatives for patients with non-immediate penicillin allergies 1
• Continue vancomycin only if the isolate is methicillin-resistant 1

Source Control is Critical

Remove any intravascular catheter immediately if bacteremia persists beyond 72 hours of appropriate antibiotics, or if there is evidence of tunnel infection, septic thrombophlebitis, or endocarditis. 1

• For catheter-related bloodstream infection with catheter removal: treat for 5-7 days 1
• If a non-tunneled catheter must be retained: treat for 10-14 days with systemic antibiotics plus antibiotic lock therapy 1
• Persistent bacteremia despite appropriate antibiotics mandates catheter removal—this is non-negotiable 1

Treatment Duration by Clinical Scenario

Uncomplicated Bacteremia (Catheter-Related)

• 5-7 days of systemic antibiotics if catheter is removed 1
• Uncomplicated means: catheter removed, negative blood cultures within 2-4 days, defervescence within 72 hours, no metastatic infection, and endocarditis excluded 2

Complicated Bacteremia

• 4-6 weeks of therapy if criteria for uncomplicated bacteremia are not met 2
• Obtain repeat blood cultures 2-4 days after initial positive cultures to document clearance 2

Native Valve Endocarditis

• Treat for 6 weeks with vancomycin (if methicillin-resistant) or nafcillin/oxacillin (if susceptible) 1
• Perform transesophageal echocardiography on all patients with S. hominis bacteremia to exclude endocarditis 2
• Do NOT routinely add gentamicin or rifampin for native valve CoNS endocarditis 1

Prosthetic Valve Endocarditis

• Minimum 6 weeks of vancomycin 30 mg/kg/day IV in 2 divided doses (trough 10-20 μg/mL) PLUS rifampin 900 mg/day in 3 divided doses, adding gentamicin 3 mg/kg/day for the first 2 weeks only 1
• This is the ONLY scenario where combination therapy with aminoglycosides is recommended for CoNS 1

Management of Persistent Bacteremia

If bacteremia persists despite 72 hours of appropriate therapy with source control, consider adding rifampin or switching to combination therapy, but catheter removal takes absolute priority. 4, 5

• Rifampin has been used successfully in refractory CoNS bacteremia, particularly in neonates, at doses of 5-10 mg/kg every 12 hours 4
• One case report demonstrated successful treatment of refractory S. hominis bacteremia with triple therapy (meropenem, vancomycin, and clindamycin) for over 3 weeks in an immunocompromised patient 5
• However, combination therapy should NOT be routine—reserve for truly refractory cases after ensuring adequate source control 1

Critical Pitfalls to Avoid

• Do NOT treat single positive blood cultures as true bacteremia—CoNS are common contaminants and require ≥2 positive cultures within 48 hours to confirm true infection 1
• Do NOT continue vancomycin if repeat cultures are negative and clinical contamination is likely 1
• Do NOT use combination therapy (vancomycin plus gentamicin or rifampin) for routine S. hominis bacteremia—this is reserved exclusively for prosthetic valve endocarditis 1
• Do NOT delay catheter removal if fever or positive cultures persist after 72 hours of appropriate antibiotics 1

Special Populations

Immunocompromised Patients

• S. hominis is particularly pathogenic in immunocompromised hosts, including those with malignancy or hypercortisolism 6, 5
• These patients may require prolonged therapy (>4 weeks) and more aggressive source control 5
• Consider infectious disease consultation for refractory cases 5