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In vitro evaluation of antibiotic elution from polymethylmethacrylate (PMMA) and mechanical assessment of
D L Weisman1, M L Olmstead, J J Kowalski
1Department of Veterinary Clinical Sciences, The Ohio State University, Columbus 43210, USA.
Objective:
To determine whether different methods of sterilization of antibiotic vials or the heat of polymerization altered the antimicrobial activity or mechanical properties of antibiotic/polymethylmethacrylate (PMMA) composites when compared to antibiotic-free PMMA.
Study Design:
In vitro study.
Methods:
Steam-sterilized, gas-sterilized, and non-sterilized 1 gram vials of cefazolin and injectable gentamicin sulfate (high and low doses) were mixed with PMMA to prepare composites for antibiotic elution evaluation, compression, and elongation testing. Blocks of PMMA that contained antibiotic were assayed for antibacterial activity using an agar gel diffusion method or were placed in phosphate buffered saline (PBS) to assess elution of antibiotic. Phosphate buffered saline samples from steam-sterilized cefazolin and high-dose gentamicin groups were assayed on days 1, 2, 5, and 9 for cefazolin or gentamicin concentration by high-pressure liquid chromatography or fluorescent polarization immunoassay, respectively.
Results:
PMMA blocks containing antibiotic inhibited bacterial growth of Staphylococcus aureus 25923 for an average of 9 days. Cefazolin and gentamicin concentration in PBS decreased dramatically after the first 24 hours, but remained above minimum inhibitory concentration (MIC) throughout the experiment for all groups except low-dose gentamicin. Compressive strength of plugs made from plain cement and plugs made from PMMA mixed with untreated and steam-sterilized cefazolin was similar, but was significantly different from the other groups. There appeared to be an inverse relationship between compressive strength and elongation.
Conclusion:
PMMA/antibiotic composites inhibited bacterial growth for 7 to 10 days. Compressive strength was affected by different additions of antibiotic.
Clinical Relevance:
Bacteria introduced during a surgical procedure may be inhibited by elution of antibiotic from PMMA at the time of contamination.
Insights
Polymethylmethacrylate (PMMA) composites with antibiotics inhibited bacterial growth for up to 10 days. Sterilization methods and antibiotic concentrations affected mechanical properties and elution, with low-dose gentamicin falling below the minimum inhibitory concentration.
Area of Science:
- Biomaterials Science
- Orthopedic Surgery
- Infectious Disease
Background:
- Polymethylmethacrylate (PMMA) bone cement is widely used in orthopedic surgery.
- The incorporation of antibiotics into PMMA can prevent surgical site infections.
- The sterilization method of antibiotic vials and polymerization heat may affect the properties of PMMA/antibiotic composites.
Purpose of the Study:
- To evaluate the impact of different antibiotic vial sterilization methods (steam, gas, non-sterilized) on the antimicrobial activity and mechanical properties of cefazolin and gentamicin/PMMA composites.
- To compare these properties with antibiotic-free PMMA.
Main Methods:
- In vitro study.
- Antibiotic-loaded PMMA composites were prepared using steam-sterilized, gas-sterilized, and non-sterilized vials.
- Antibiotic elution was assessed using phosphate-buffered saline (PBS) and high-pressure liquid chromatography or fluorescent polarization immunoassay.
- Antimicrobial activity was determined by agar gel diffusion.
- Mechanical properties (compression, elongation) were tested.
Main Results:
- PMMA/antibiotic composites demonstrated antibacterial activity against Staphylococcus aureus for an average of 9 days.
- Antibiotic concentrations in PBS decreased significantly within 24 hours but remained above the minimum inhibitory concentration (MIC) for most groups.
- Low-dose gentamicin elution fell below MIC.
- Compressive strength was similar for plain PMMA and PMMA with untreated or steam-sterilized cefazolin, but differed significantly from other groups.
- An inverse relationship between compressive strength and elongation was observed.
Conclusions:
- PMMA/antibiotic composites provide sustained antimicrobial activity for 7-10 days.
- Sterilization methods and antibiotic loading influence the mechanical properties of PMMA composites.
- Elution of antibiotics from PMMA can inhibit bacteria introduced during surgery.