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Efficacy of Vancomycin with Fosfomycin against Vancomycin-Resistant Enterococcus Strains Using Agar Dilution Method
Clinical Laboratory
|January 25, 2021
Summary
Vancomycin combined with fosfomycin demonstrates 100% synergy against vancomycin-resistant Enterococci (VRE) strains in vitro. This combination therapy shows promise for treating VRE infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Enterococcus faecalis and Enterococcus faecium are significant causes of community-acquired and nosocomial infections.
- Combination antibiotic therapy offers advantages over monotherapy due to synergistic effects.
- Vancomycin-resistant Enterococci (VRE) pose a growing therapeutic challenge.
Purpose of the Study:
- To evaluate the in vitro synergistic activity of vancomycin combined with fosfomycin against clinical VRE strains.
- To determine the efficacy of this combination using agar dilution and time-kill curve methods.
Main Methods:
- Thirty clinical VRE strains were analyzed using conventional identification methods.
- Antibiotic susceptibility was assessed via broth microdilution for vancomycin and agar dilution for fosfomycin.
- Fractional Inhibitory Concentration Index (FICI) was calculated to determine synergy (FICI ≤ 0.5), with time-kill curves verifying results for two strains.
Main Results:
- Fosfomycin susceptibility was observed in 16.6% (5/30) of VRE strains.
- Vancomycin MIC50/90 values were 512 mg/L, while fosfomycin MIC50/90 values were 128 mg/L.
- A 100% rate of synergism was observed for the vancomycin-fosfomycin combination.
Conclusions:
- The combination of vancomycin and fosfomycin exhibits significant in vitro synergy against VRE.
- This synergistic combination represents a potential therapeutic option for treating VRE infections.
