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Efficacy of cefoperazone in combination with sulbactam in experimental Staphylococcus aureus endocarditis in rabbits
1Department of Medicine, San Francisco General Hospital, CA 94110.
Abstract:
The activity of cefoperazone with and without sulbactam was studied in vitro and in vivo against strains of methicillin-resistant and methicillin-susceptible Staphylococcus aureus. Cefoperazone with or without sulbactam was inactive in vitro against the methicillin-resistant strain and was bound by penicillin-binding protein 2a with an IC50 of 190 mg/L (the concentration that reduced radio-labelling with 3H-penicillin by 50%). Cefoperazone was hydrolysed by beta-lactamase in vitro but sulbactam improved cefoperazone activity in a rabbit model of aortic valve endocarditis caused by a beta-lactamase producing methicillin-susceptible strain.
Insights
Cefoperazone showed limited activity against methicillin-resistant Staphylococcus aureus in vitro. However, sulbactam enhanced cefoperazone
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant threat due to antibiotic resistance.
- Beta-lactam antibiotics, like cefoperazone, are often ineffective against MRSA.
- Penicillin-binding protein 2a (PBP2a) is a key determinant of methicillin resistance in S. aureus.
Purpose of the Study:
- To evaluate the in vitro and in vivo activity of cefoperazone, with and without sulbactam, against Staphylococcus aureus strains.
- To investigate the mechanism of cefoperazone resistance in MRSA.
- To assess the efficacy of cefoperazone/sulbactam in a relevant animal model.
Main Methods:
- In vitro susceptibility testing against methicillin-resistant and methicillin-susceptible S. aureus strains.
- Binding assays to determine the interaction of cefoperazone with PBP2a.
- In vivo efficacy study using a rabbit model of aortic valve endocarditis.
Main Results:
- Cefoperazone, alone or with sulbactam, was inactive in vitro against MRSA.
- Cefoperazone bound to PBP2a with an IC50 of 190 mg/L, indicating resistance.
- Sulbactam improved cefoperazone activity in vivo against a beta-lactamase-producing methicillin-susceptible S. aureus strain in a rabbit endocarditis model.
Conclusions:
- Cefoperazone is ineffective against MRSA due to PBP2a binding.
- Sulbactam, a beta-lactamase inhibitor, can restore cefoperazone activity against susceptible strains producing beta-lactamase.
- These findings highlight the challenges of treating MRSA infections and the potential role of combination therapy for susceptible strains.