Is Fosfomycin (generic name) effective against Enterococcus faecalis in urinary tract infections (UTIs)?

From the Guidelines

Fosfomycin is effective against Enterococcus faecalis in urinary tract infections (UTIs). Fosfomycin tromethamine (typically sold as Monurol) is administered as a single 3-gram oral dose for uncomplicated UTIs caused by E. faecalis, as recommended by guidelines 1. This one-time dosing regimen offers excellent patient compliance compared to multi-day antibiotic courses. Fosfomycin works by inhibiting bacterial cell wall synthesis through a unique mechanism different from other antibiotics, which helps explain its effectiveness against many resistant organisms, including E. faecalis. The drug achieves high concentrations in the urinary tract and maintains therapeutic levels for 24-48 hours after a single dose. It has minimal impact on the normal intestinal flora and low resistance rates. However, fosfomycin should be taken on an empty stomach with water, and patients should be aware that it may cause mild gastrointestinal side effects such as diarrhea, nausea, or headache in some cases. For complicated UTIs involving E. faecalis, additional doses or alternative antibiotics might be necessary based on susceptibility testing.

Some key points to consider when using fosfomycin for UTIs caused by E. faecalis include:

• Fosfomycin has in vitro activity against vancomycin-resistant enterococci (VRE) 1
• The single-dose regimen of fosfomycin offers convenience and excellent patient compliance 1
• Fosfomycin has minimal impact on the normal intestinal flora and low resistance rates 1
• The drug should be taken on an empty stomach with water to maximize its effectiveness 1

It's essential to note that while fosfomycin is effective against E. faecalis, it's crucial to differentiate between colonization and true infection before initiating treatment, as recommended by guidelines 1. Additionally, for complicated UTIs or those involving other resistant organisms, alternative antibiotics or combination therapy may be necessary, as suggested by studies 1.

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 is effective against Enterococcus faecalis in urinary tract infections (UTIs), specifically uncomplicated urinary tract infections (acute cystitis) in women due to susceptible strains of Enterococcus faecalis 2.

• Key points:
  • Fosfomycin tromethamine granules for oral solution is indicated for the treatment of uncomplicated UTIs due to Enterococcus faecalis.
  • Fosfomycin has in vitro activity against a broad range of gram-positive and gram-negative aerobic microorganisms, including Enterococcus faecalis.
  • The bactericidal action of fosfomycin is due to its inactivation of the enzyme enolpyruvyl transferase, thereby irreversibly blocking bacterial cell wall synthesis 2.

From the Research

Fosfomycin Effectiveness Against Enterococcus faecalis

• Fosfomycin has been shown to be effective against Enterococcus faecalis in urinary tract infections (UTIs) 3, 4, 5, 6, 7.
• Studies have demonstrated that fosfomycin has in vitro activity against E. faecalis, including vancomycin-resistant strains 5, 7.
• The minimum inhibitory concentration (MIC) of fosfomycin for E. faecalis has been reported to be between 4-64 μg/mL 3, 5.

Mechanism of Action and Susceptibility

• Fosfomycin works by inhibiting the MurA enzyme involved in peptidoglycan synthesis, which is essential for bacterial cell wall formation 5.
• The susceptibility of E. faecalis to fosfomycin has been evaluated using various methods, including agar dilution and ETEST 3, 6.
• The results of these studies have shown that fosfomycin is effective against E. faecalis, with a high percentage of isolates being susceptible to the antibiotic 5, 6.

Clinical Implications

• Fosfomycin may be a useful treatment option for UTIs caused by E. faecalis, particularly in cases where other antibiotics are not effective 7.
• The use of fosfomycin for the treatment of E. faecalis UTIs should be guided by susceptibility testing and clinical judgment 3, 6.
• Further studies are needed to fully evaluate the effectiveness and safety of fosfomycin for the treatment of E. faecalis UTIs 4, 7.