What is the length of treatment (LOT) for Staphylococcus hominis bacteremia sensitive to oxacillin?

Treatment Duration for Oxacillin-Sensitive Staphylococcus hominis Bacteremia

For oxacillin-sensitive Staphylococcus hominis bacteremia, treat for 10-14 days if uncomplicated (catheter-related with prompt removal, no endocarditis, blood cultures clearing within 72 hours, and defervescence within 72 hours), or 4-6 weeks if complicated by persistent bacteremia, endocarditis, or metastatic infection. 1

Determining Uncomplicated vs. Complicated Bacteremia

The treatment duration hinges on whether the infection is uncomplicated or complicated:

Uncomplicated Bacteremia (10-14 days)

Treat for 10-14 days if ALL of the following criteria are met: 1

• Catheter removed (if catheter-related) or primary bacteremia identified
• Follow-up blood cultures at 72 hours are negative 1
• Patient becomes afebrile within 72 hours of starting effective therapy 1
• No evidence of endocarditis on echocardiography 1
• No metastatic sites of infection (no osteomyelitis, discitis, or septic emboli) 1, 2

Important caveat: S. hominis is a coagulase-negative staphylococcus, which is generally more benign than S. aureus, and catheter salvage with systemic antibiotics for 10-14 days may be attempted if there are no complications. 1 However, if the catheter is removed, 5-7 days may be sufficient in truly uncomplicated cases. 1

Complicated Bacteremia (4-6 weeks)

Treat for 4-6 weeks if ANY of the following are present: 1

• Positive blood cultures persisting 72 hours after catheter removal 1
• Endocarditis confirmed on echocardiography (transesophageal echocardiography is superior to transthoracic) 1
• Suppurative thrombophlebitis 1
• Metastatic complications including:
  • Osteomyelitis or discitis (requires 6-8 weeks) 1, 2
  • Septic emboli to spleen, kidneys, or other organs 2
  • Prosthetic device involvement 1

Specific Treatment Regimen

For oxacillin-sensitive S. hominis, use an antistaphylococcal penicillin: 1

• Oxacillin 8-12 g/24 hours IV divided into 3-4 doses (typically 2 g every 4-6 hours) 1, 3
• Alternative: Nafcillin 2 g IV every 4 hours 2

Consider adding gentamicin 3 mg/kg/24 hours IV (maximum 240 mg/day) divided into 2-3 doses for the first 3-5 days for native valve infections, though this is more established for S. aureus than coagulase-negative staphylococci. 1

Critical Management Steps

Source Control

• Remove infected catheters immediately for S. hominis bacteremia, as this is the most common source. 1
• Failure to remove the catheter increases risk of complications and treatment failure. 1

Monitoring Requirements

• Obtain repeat blood cultures at 2-4 days (72 hours) after initiating therapy to document clearance. 1
• Day 1 of treatment duration is counted from the first negative blood culture, not from initiation of antibiotics. 1

Echocardiography

• Perform echocardiography to evaluate for endocarditis, particularly if bacteremia persists beyond 72 hours. 1
• Transesophageal echocardiography is most sensitive when performed 5-7 days after onset of bacteremia. 1

Common Pitfalls to Avoid

Do not treat for less than 14 days in uncomplicated bacteremia, as short-course therapy (<14 days) is significantly associated with relapse (7.9% vs 0% for ≥14 days). 4 This recommendation, while studied in S. aureus, should be applied to S. hominis given the similar pathophysiology.

Do not use inadequate dosing of beta-lactams, as total daily doses of penicillinase-stable penicillin <4 g are associated with increased mortality (OR 3.7) and doses <3 g with increased recurrence (OR 3.9). 5 Use at least 8 g/day of oxacillin divided into multiple doses. 1

Do not assume uncomplicated bacteremia without imaging, as S. hominis can cause embolic complications (splenic/renal infarcts) and discitis even when initially appearing benign. 2

Do not attempt catheter salvage if there are any signs of complications including tunnel infection, pocket infection, or persistent fever beyond 72 hours. 1