Vancomycin is NOT the appropriate antibiotic for urinary tract infections caused by resistant Gram-positive organisms
Vancomycin should not be used for UTIs, even when caused by vancomycin-resistant enterococci (VRE), because it achieves inadequate urinary concentrations and superior alternatives exist. 1
Recommended Treatment for VRE Urinary Tract Infections
Complicated VRE UTI (symptomatic with systemic signs)
- Linezolid 600 mg IV every 12 hours for 5-7 days (strong recommendation, 1C evidence) 1
- Daptomycin 6-12 mg/kg IV once daily for 5-7 days (weak recommendation, 2D evidence) 1
Uncomplicated VRE UTI (cystitis symptoms only)
- Fosfomycin 3 g PO single dose or every other day for 3-7 days (weak recommendation, 2D evidence) 1
- Nitrofurantoin 100 mg PO four times daily for 3-7 days (weak recommendation, 2D evidence) 1
- Ampicillin 18-30 g/day IV in divided doses for 3-7 days (weak recommendation, 2D evidence) 1
- Amoxicillin 500 mg PO/IV every 8 hours for 3-7 days (weak recommendation, 2D evidence) 1
Critical Clinical Considerations
Why Vancomycin Fails in UTI
Vancomycin was historically used for serious staphylococcal infections and endocarditis, not urinary tract infections. 2 The drug achieves poor urinary concentrations and lacks the pharmacokinetic profile needed for effective UTI treatment.
Ampicillin for Ampicillin-Resistant VRE
High-dose ampicillin (18-30 g IV daily) or amoxicillin (500 mg every 8 hours) can overcome ampicillin resistance in VRE UTIs because urinary concentrations far exceed serum MICs. 1 One retrospective study showed 88.1% clinical cure and 86% microbiological eradication in ampicillin-resistant VRE UTIs treated with ampicillin. 1
Daptomycin Dosing Adjustments
For patients with normal to moderately impaired renal function, use daptomycin ≥5 mg/kg every 24 hours. 3 For severe kidney disease, extend the interval to every 48 hours. 3 Daptomycin achieved 100% clinical cure and VRE eradication in a case series of 10 patients with VRE UTI, regardless of renal function or catheter use. 3
Nitrofurantoin Resistance Trends
Emerging resistance to nitrofurantoin has been documented, with rates climbing from near zero to 40% in some centers over the past decade. 4 Despite this trend, nitrofurantoin remains appropriate for uncomplicated VRE UTI when susceptibility is confirmed. 4
Common Pitfalls to Avoid
Do not treat asymptomatic bacteriuria. Approximately 58% of VRE-positive urine cultures represent colonization or asymptomatic bacteriuria rather than true infection. 5 Differentiate colonization from infection before prescribing anti-VRE agents. 1
Do not use vancomycin empirically for suspected VRE UTI. Overtreatment occurred in 58% of noncompliant cases in one study, leading to unnecessary drug costs and potential toxicity. 5
Remove indwelling catheters when possible. Indwelling catheters are independently associated with clinical failure (OR 4.62; 95% CI 1.05-18.24). 5
Risk Factors for Clinical Failure
Independent predictors of treatment failure include:
- Weight ≥100 kg (OR 5.30; 95% CI 1.42-12.21) 5
- Renal disease (OR 2.57; 95% CI 1.02-6.47) 5
- Indwelling catheter (OR 4.62; 95% CI 1.05-18.24) 5
- VRE bloodstream infection (OR 15.71; 95% CI 2.9-128.7) 5
Alternative Agents for Refractory Cases
If linezolid or daptomycin fail despite adequate treatment: