From the Guidelines
Fosfomycin is effective against Enterococcus faecalis urinary tract infections (UTIs), as evidenced by its recommendation for uncomplicated UTIs due to VRE in recent guidelines 1. The standard dosage for uncomplicated UTIs is a single 3-gram sachet of fosfomycin tromethamine dissolved in water, taken orally as a one-time dose.
- Fosfomycin works by inhibiting bacterial cell wall synthesis through a unique mechanism different from other antibiotics, specifically by inhibiting the enzyme phosphoenolpyruvate transferase.
- This unique mechanism helps explain why fosfomycin maintains good activity against many multidrug-resistant organisms, including E. faecalis.
- The drug achieves high concentrations in urine and maintains effective levels for several days after a single dose.
- Fosfomycin is particularly valuable for treating E. faecalis UTIs because of increasing resistance to other antibiotics among enterococci. Some key points to consider when using fosfomycin for UTIs include:
- Patients should take fosfomycin on an empty stomach or at least 2-3 hours after a meal for optimal absorption.
- Fosfomycin has been shown to be effective against VRE in uncomplicated UTIs, with a weak recommendation and very low quality of evidence 1.
- The clinical efficacy of fosfomycin is comparable to other first-line agents, although its bacterial efficacy may be lower 1. Overall, fosfomycin is a useful option for treating E. faecalis UTIs, particularly in cases where resistance to other antibiotics is a concern.
From the FDA Drug Label
Fosfomycin tromethamine granules for oral solution is indicated only for the treatment of uncomplicated urinary tract infections (acute cystitis) in women due to susceptible strains of Escherichia coli and Enterococcus faecalis. Fosfomycin has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section: Aerobic gram-positive microorganisms Enterococcus faecalis Aerobic gram-negative microorganisms Escherichia coli
Fosfomycin covers Enterococcus faecalis in urinary tract infections (UTIs), as it is indicated for the treatment of uncomplicated UTIs due to susceptible strains of Enterococcus faecalis 2.
From the Research
Fosfomycin Coverage for Enterococcus faecalis in UTIs
- Fosfomycin has been shown to be effective against Enterococcus faecalis in urinary tract infections (UTIs) 3, 4, 5, 6, 7
- The antibiotic has a broad spectrum of activity and is bactericidal, making it a potential option for treating UTIs caused by E. faecalis 3, 5
- Studies have demonstrated that fosfomycin has high activity against E. faecalis, with susceptibility rates ranging from 94.4% to 99.6% 4, 6
- Fosfomycin has also been shown to be effective against vancomycin-resistant Enterococcus (VRE) and other drug-resistant isolates 4, 6, 7
Mechanism of Action and Resistance
- Fosfomycin works by inhibiting the MurA enzyme, which is involved in peptidoglycan synthesis, making it a time-dependent inhibitor 5
- Resistance to fosfomycin can arise through loss of active transport mechanisms, but this is rarely seen during therapy of UTIs 5
- The low fitness of resistant organisms may contribute to the rarity of resistance during UTI treatment 5
Clinical Efficacy and Susceptibility Testing
- Fosfomycin has been shown to be effective in clinical trials for the treatment of UTIs, including those caused by E. faecalis 3, 4, 6
- Susceptibility testing for fosfomycin can be performed using agar dilution or Etest methods, although the latter is only approved by EUCAST 6
- Fosfomycin susceptibility profiles have been compared to other first-line antibiotics, and it has been found to be effective against isolates producing extended-spectrum beta-lactamases and those resistant to other first-line treatments 6