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Fusidic acid alone or in combination with vancomycin for therapy of experimental endocarditis due to
B Fantin1, R Leclercq, J Duval
1Institut National de la Santé et de la Recherche Médicale, Unité 13, Service de Médecine Interne, Hôpital Bichat, Paris, France.
Abstract:
The usefulness of fusidic acid, alone or combined with vancomycin, was investigated for the therapy of experimental endocarditis caused in rabbits by a methicillin-resistant strain of Staphylococcus aureus. In vitro killing curves showed an indifferent interaction between the two antibiotics. In vivo, vancomycin alone was as effective as a vancomycin-fusidic acid combination (P < 0.05 versus control animals). No resistance to fusidic acid emerged during combination therapy. Fusidic acid alone was not effective. Resistance emerged in 5 of 12 animals treated with fusidic acid alone and was responsible for antibacterial failure. Fusidic acid alone was effective (P < 0.001) and did not select resistant strains if therapy was started when animals retained a smaller inoculum. We concluded that the vancomycin-fusidic acid combination exhibited no advantage over vancomycin alone in this model.
Insights
Vancomycin alone effectively treated experimental Staphylococcus aureus endocarditis in rabbits. Combining vancomycin with fusidic acid showed no added benefit and did not prevent fusidic acid resistance.
Area of Science:
- Infectious Diseases
- Microbiology
- Pharmacology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant threat in healthcare settings.
- Bacterial endocarditis is a serious infection requiring effective antimicrobial therapy.
- Fusidic acid is an antibiotic used against Gram-positive bacteria, including S. aureus.
Purpose of the Study:
- To evaluate the efficacy of fusidic acid, alone or in combination with vancomycin, for treating experimental MRSA endocarditis in rabbits.
- To assess the emergence of antibiotic resistance during therapy.
- To compare the combination therapy with vancomycin monotherapy.
Main Methods:
- Experimental endocarditis was induced in rabbits using a methicillin-resistant Staphylococcus aureus strain.
- In vitro killing curves were used to determine antibiotic interactions.
- Animals were treated with vancomycin alone, vancomycin plus fusidic acid, or fusidic acid alone.
- Antibacterial efficacy and resistance development were monitored.
Main Results:
- In vitro, vancomycin and fusidic acid showed an indifferent interaction.
- In vivo, vancomycin alone was as effective as the vancomycin-fusidic acid combination (P < 0.05 vs. controls).
- Fusidic acid alone was ineffective and led to resistance in 5 of 12 animals, although it was effective when started with a smaller bacterial inoculum.
Conclusions:
- The combination of vancomycin and fusidic acid offers no therapeutic advantage over vancomycin alone in this experimental endocarditis model.
- Fusidic acid monotherapy is associated with a high risk of resistance development.
- Early intervention with fusidic acid may be effective if initiated with a low bacterial burden.