The Journal of Bone and Joint Surgery (American). 2009;91:2683-2692.
doi:10.2106/JBJS.H.01699
© 2009 The Journal of Bone and Joint Surgery, Inc.
The Effects of Farnesol on Staphylococcus aureus Biofilms and OsteoblastsAn in Vitro Study
Aasis Unnanuntana, MD1,
Lindsay Bonsignore, BS1,
Mark E. Shirtliff, PhD2 and
Edward M. Greenfield, PhD1
1 Departments of Orthopaedics (A.U., L.B., and E.M.G), Pathology (L.B. and E.M.G.), and Physiology and Biophysics (E.M.G.), University Hospitals Case Medical Center, Case Western Reserve University School of Medicine, 11100 Euclid Avenue, Cleveland, OH 44106. E-mail address for A. Unnanuntana: uaasis{at}yahoo.com
2 Department of Microbiology and Immunology, School of Medicine, University of Maryland at Baltimore, 650 West Baltimore Street, Baltimore, MD 21201
Investigation performed at University Hospitals Case Medical Center, Case Western Reserve University School of Medicine, Cleveland, Ohio
Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants in excess of $10,000 from the Sulzer Settlement Medical Research Trust Fund and the Department of Orthopaedics, University Hospitals Case Medical Center, Case Western Reserve University. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.
Background: Bacterial biofilms play a major role in chronic orthopaedic infections. Recently, farnesol (an antifungal agent) has been shown to express antimicrobial activities against Staphylococcus aureus and Streptococcus mutans. However, the effects of farnesol on the formation of bacterial biofilms on orthopaedic biomaterials and its effects on osteoblasts have not been investigated, to our knowledge, and are therefore the focus of this study.
Methods: Biofilms of Staphylococcus aureus (Seattle 1945GFPuvr) were grown on titanium alloy discs. The effects of soluble farnesol on biofilm formation with or without gentamicin were examined with fluorescence microscopy and in quantitative cultures. The effect of farnesol coated on titanium alloy discs was also investigated, as was the effect of the agent on MC3T3-E1 pre-osteoblastic cells cultured on titanium alloy discs.
Results: Soluble farnesol at a 30-mM concentration reduced the number of viable bacteria 104-fold and completely inhibited biofilm formation. Low concentrations of soluble farnesol (0.03 to 3 mM) did not inhibit biofilm formation and did not potentiate the effect of a submaximal concentration of gentamicin. Dried farnesol on titanium alloy discs reduced the number of viable bacteria fiftyfold. The effect of farnesol on bacterial biofilm formation lasted for at least three days. Soluble farnesol added after the biofilm had already formed also reduced the final number of viable bacteria, by fifty-six-fold. Soluble farnesol (3-mM and 30-mM concentrations) inhibited spreading of the MC3T3-E1 cells.
Conclusions: In vitro, a high concentration of farnesol (30 mM) shows antimicrobial properties against bacterial biofilms; however, it also has a negative effect on pre-osteoblasts. Farnesol can also express antimicrobial activity when predried on titanium discs and when added to preformed biofilms.
Clinical Relevance: As musculoskeletal infections remain a complicated problem, development of novel interventions to enhance prevention or treatment is necessary. Our study provides a basic knowledge of the effectiveness of farnesol against Staphylococcus aureus biofilms on titanium alloy surfaces. Although farnesol may have a clinical role, additional investigations, both in vitro and in vivo, are needed.

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