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In vitro activity of vancomycin against enterococci.
P N Poulsen1, S H Hartzen, H Rasmusen
1Department of Antibiotics, Statens Seruminstitut, Copenhagen, Denmark.
Summary
Vancomycin effectively inhibited enterococci in vitro, but failed to demonstrate a bactericidal effect. This study highlights vancomycin
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Enterococci are significant human pathogens.
- Vancomycin is a critical antibiotic for treating Gram-positive bacterial infections.
- Understanding vancomycin's activity against enterococci is crucial for effective treatment strategies.
Purpose of the Study:
- To evaluate the in vitro activity of vancomycin against clinical isolates of enterococci.
- To determine both the inhibitory (MIC) and bactericidal (MBC) effects of vancomycin.
- To assess the reliability of MBC determination by controlling technical factors.
Main Methods:
- Macro-tube dilution method for Minimum Inhibitory Concentration (MIC) determination.
- Quantitative killing curve procedures for Minimum Bactericidal Concentration (MBC) assessment.
- Use of a standardized filtered ox broth medium and early logarithmic growth phase inoculum.
Main Results:
- Vancomycin exhibited good in vitro inhibitory activity against enterococci.
- MIC90 values ranged from 1.6 to 3.1 µg/ml for different species (S. faecalis, S. faecium, S. durans).
- No bactericidal effect was observed, with MBCs consistently greater than 100 µg/ml.
Conclusions:
- Vancomycin demonstrates potent in vitro bacteriostatic activity against enterococci.
- The lack of a demonstrated bactericidal effect suggests limitations in vancomycin's ability to eradicate enterococcal infections.
- Further investigation into alternative or combination therapies may be warranted for enterococcal infections.