Antibiotic Treatment for Gram-Positive Cocci UTIs
For uncomplicated UTIs caused by gram-positive cocci (primarily enterococci and staphylococci), use nitrofurantoin or fosfomycin as first-line therapy, with ampicillin reserved for susceptible enterococcal infections. 1
First-Line Empiric Therapy
- Nitrofurantoin is FDA-approved for lower UTI treatment and demonstrates good in vitro activity against vancomycin-resistant enterococci (VRE) and gram-positive uropathogens 1, 2
- Fosfomycin is FDA-approved specifically for UTI caused by E. faecalis and shows in vitro activity against VRE, with promising results in retrospective studies for uncomplicated UTIs 1
- These agents should be used for 5-7 days maximum for acute cystitis episodes, avoiding prolonged courses 1
Organism-Specific Considerations
For Enterococcal UTIs:
- Ampicillin (high-dose: 18-30 g IV daily) or amoxicillin (500 mg PO/IV every 8 hours) remains the drug of choice for ampicillin-susceptible enterococcal infections 1
- High urinary concentrations of ampicillin can overcome resistance in ampicillin-resistant VRE UTIs, achieving 88.1% clinical cure and 86% microbiological eradication 1
- For ampicillin-susceptible isolates, combination therapy with ampicillin plus gentamicin provides synergistic bactericidal activity 1
For Staphylococcal UTIs:
- Ciprofloxacin and amoxicillin show good activity against gram-positive cocci including staphylococci 2
- Newer fluoroquinolones like levofloxacin or gatifloxacin provide coverage for gram-positive uropathogens 3
Resistant Organisms
For Vancomycin-Resistant Enterococci (VRE):
- Linezolid demonstrates comparable activity to ciprofloxacin against fluoroquinolone-susceptible gram-positive uropathogens and maintains activity against fluoroquinolone-resistant strains 3
- Daptomycin (8-12 mg/kg) is preferred for serious VRE infections due to bactericidal activity, though it should not be used for VRE bacteremia due to low serum levels 1
- Tigecycline is not recommended for VRE UTI due to large volume of distribution and inadequate serum/urinary levels 1
Critical Pitfalls to Avoid
- Do not treat asymptomatic bacteriuria in non-pregnant patients, even with positive cultures showing gram-positive cocci 1
- Avoid single-dose aminoglycosides for complicated UTIs; they are only appropriate for simple cystitis 4
- Do not use ceftaroline empirically for enterococcal coverage, as it has poor activity against enterococci despite broad gram-positive spectrum 1
- Obtain urine cultures prior to treatment to guide therapy based on susceptibilities, particularly for recurrent infections 1
Treatment Duration
- Uncomplicated lower UTI: 5-7 days maximum 1
- Complicated UTI: 7-14 days, with adjustment based on clinical response and culture results 4
- Males (when prostatitis cannot be excluded): 14 days 4