Treatment of Oxacillin-Resistant Staphylococcus epidermidis Urinary Tract Infection
For oxacillin-resistant S. epidermidis UTI, vancomycin is the definitive first-line treatment, with linezolid as an equally effective alternative for uncomplicated cases. 1
Initial Empiric Therapy
- Start vancomycin empirically because most coagulase-negative staphylococci (CoNS), including S. epidermidis, are methicillin-resistant in healthcare settings. 1
- Target vancomycin trough levels of 10-15 mg/L for CoNS infections. 1
- Vancomycin dosing: 30 mg/kg/day IV in 2 divided doses (typically 1 g every 12 hours in adults with normal renal function), targeting trough 10-20 μg/mL. 1, 2
Alternative First-Line Options for Uncomplicated UTI
- Linezolid 600 mg IV or PO every 12 hours is equally effective for CoNS infections and may be preferred for uncomplicated UTI due to excellent urinary penetration and oral bioavailability. 3, 4
- Linezolid achieved comparable clinical cure rates (73.2%) to vancomycin (73.1%) in MRSA infections, with similar tolerability. 4
Treatment Duration
- For uncomplicated UTI with catheter removal: Treat for 5-7 days with systemic antibiotics. 1
- For complicated UTI or pyelonephritis: Treat for 10-14 days if follow-up cultures are negative and no metastatic infection exists. 5
- If catheter retained (non-tunneled): Treat for 10-14 days with systemic antibiotics plus antibiotic lock therapy. 1
Critical Management Steps
- Remove any indwelling urinary catheter immediately if present, as this is the most common source of CoNS infection and treatment failure is common without removal. 1, 6
- Obtain repeat urine cultures at 72 hours after initiating therapy to document clearance. 5
- Do not use cephalosporins for oxacillin-resistant S. epidermidis—cross-resistance exists despite in vitro susceptibility results showing cephalosporin sensitivity. 3, 6
When to Escalate or Modify Therapy
- Persistent bacteriuria or fever after 72 hours of appropriate antibiotics mandates catheter removal if not already done and consideration of metastatic infection. 1
- For severe or complicated infections (pyelonephritis, bacteremia), consider adding rifampin 900 mg/day in 3 divided doses to vancomycin, though this is more established for prosthetic device infections than simple UTI. 1, 6
- Daptomycin is NOT recommended for UTI as it is inactivated by pulmonary surfactant and has poor urinary activity, despite one small case series suggesting benefit. 7
Common Pitfalls to Avoid
- Do not dismiss S. epidermidis as a contaminant in patients with urinary abnormalities (vesicoureteral reflux, obstruction) or those on antibiotic prophylaxis—it can cause true pyelonephritis even in immunocompetent patients. 8
- Do not use combination therapy (vancomycin plus gentamicin or rifampin) for routine CoNS UTI—reserve combinations for prosthetic valve endocarditis only. 1
- Do not continue vancomycin if repeat cultures are negative and contamination is suspected—CoNS require ≥2 positive cultures within 48 hours to confirm true infection. 1