Efficacy of linezolid in treatment of experimental endocarditis caused by methicillin-resistant Staphylococcus aureus

Area of Science:

• Infectious Diseases
• Pharmacology
• Microbiology

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant threat, particularly in serious infections like endocarditis.
• Vancomycin is a standard treatment, but antimicrobial resistance necessitates exploring alternative therapies.
• Linezolid, an oxazolidinone antibiotic, offers a potential treatment option for resistant bacterial infections.

Purpose of the Study:

• To investigate the efficacy of orally dosed linezolid compared to intravenously dosed vancomycin against MRSA experimental aortic-valve endocarditis in rabbits.
• To determine the relationship between linezolid plasma concentrations and its therapeutic effect in this infection model.

Main Methods:

• Experimental aortic-valve endocarditis was established in rabbits using a clinical MRSA isolate.
• Rabbits were treated with varying doses of oral linezolid (25, 50, 75 mg/kg) or intravenous vancomycin (25 mg/kg) for 5 days.
• Bacterial counts in valve vegetations, mortality rates, and plasma drug concentrations were assessed.

Main Results:

• Linezolid at 50 and 75 mg/kg, and vancomycin, significantly reduced bacterial counts compared to controls.
• The highest dose of linezolid (75 mg/kg) demonstrated efficacy similar to vancomycin, with reduced bacterial counts and a high rate of culture-negative valves.
• Linezolid efficacy correlated with plasma trough concentrations remaining above the minimum inhibitory concentration (MIC).

Conclusions:

• Oral linezolid can be effective against MRSA experimental aortic-valve endocarditis in rabbits, particularly at higher doses (50-75 mg/kg).
• Therapeutic success with linezolid is linked to maintaining plasma concentrations above the MIC.
• Linezolid presents a promising alternative for treating severe staphylococcal infections, especially in cases of resistance to other antibiotics.