Inhibitory effects of vancomycin and fosfomycin on methicillin-resistant Staphylococcus aureus from...

Area of Science:

• Orthopedics
• Infectious Diseases
• Pharmacology

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) infections pose a significant clinical challenge.
• Vancomycin and fosfomycin are commonly employed antibiotics for MRSA treatment.
• Articulating cement spacers are utilized in orthopedic surgery to deliver antibiotics locally.

Purpose of the Study:

• To compare the in vitro inhibitory efficacy of vancomycin versus fosfomycin in antibiotic-impregnated articulating cement spacers against MRSA.
• To evaluate the duration of antibiotic activity from these spacers.
• To assess the suitability of these antibiotic delivery systems for managing MRSA bone infections.

Main Methods:

• Preparation of vancomycin- and fosfomycin-impregnated articulating cement spacers.
• Incubation of spacers in phosphate-buffered saline (PBS) and collection of aliquots over time.
• Assessment of MRSA inhibitory activity using the disc diffusion method.
• Measurement of inhibition zone diameters and statistical analysis (Wilcoxon Rank Sum Test).

Main Results:

• Vancomycin spacers demonstrated significantly larger MRSA inhibition zones compared to fosfomycin spacers from day three up to four weeks (p < 0.001).
• Vancomycin maintained MRSA inhibitory activity for the entire four-week study period.
• Fosfomycin spacers exhibited inhibitory activity for only three days, after which MRSA inhibition was not observed.

Conclusions:

• Vancomycin-impregnated articulating cement spacers exhibit superior and more prolonged in vitro inhibitory effects against MRSA than fosfomycin-impregnated spacers.
• The findings suggest vancomycin is a more effective antibiotic for impregnation in articulating cement spacers for MRSA management.
• Potential limitations of the disc diffusion bioassay for highly soluble antibiotics at high concentrations warrant consideration in future studies.