Mechanical effects, antimicrobial efficacy and cytotoxicity of usnic acid as a biofilm prophylaxis in PMMA

Abstract

Experiments were performed to test the null hypothesis that the addition of a natural occurring antibiotic would not alter mechanical properties of polymethylmethacrylate (PMMA). Compression and four-point bending tests were used to assess mechanical properties of zirconium dioxide bearing bone cement (Type Zr) and barium sulfate bearing bone cement (Type Ba), mixed with the antibiotic usnic acid ("usnic"), used to create a surface resistant to biofilm formation. Addition of usnic had a statistically significant effect on the material properties. Compressive and bending strengths decreased as usnic was added and Type Zr was stronger than Type Ba although material properties remained above recommended minima. With implications of liver toxicity with large doses of usnic taken as a dietary supplement, cytotoxicity tests using bone cement coupons were performed and showed very little or no toxicity in primary cultures of rabbit skin derived fibroblasts. A simple test of usnic's efficacy as a biofilm prophylaxis in PMMA was also conducted. Bone cement coupons with usnic were tested for their effectiveness against methicillin resistant Staphylococcus aureus. Diminished biofilm formation on usnic-containing coupons indicated that usnic can be an effective anti-microbial agent.

Release behavior and antibiofilm activity of usnic acid-loaded carboxylated poly(l-lactide) microparticles

“…As for the antimicrobial activity, UA is active against methicillin-resistant Staphylococcus aureus [10], Staphylococcus epidermidis [11], Enterococcus faecalis and Enterococcus faecium [12], Candida species [13], and Mycobacterium tuberculosis [14]. UA has also been reported to control biofilm formation by staphylococcal species [15,16] that are known to be among the most leading causative agents of nosocomial infections [17]. In addition, recently, Gupta et al [18] showed that UA exerts its antibacterial activity against methicillin-resistant S. aureus by disruption of the cell membrane, highlighting a potential UA activity also toward slowly growing or dormant cells present in the biofilm.…”

In vitro antimicrobial activity of the organic extract of Cladonia substellata Vainio and usnic acid against Staphylococcus spp. obtained from cats and dogs

“…This recommends usnic acid as a new active ingredient for a pharmaceutical formulation that could be used in the prevention and treatment of gingival and periodontal diseases. Kim et al (2011) also examined the inhibition of biofilm by usnic acid, as well as the antimicrobial efficacy and cytotoxicity of the compound. The authors showed the effectiveness of usnic acid as an antimicrobial to be used in the prevention of biofilm production by Staphylococcus spp.…”

Design and characterization of antimicrobial usnic acid loaded-core/shell magnetic nanoparticles

“…Our group has lately developed an intrinsically antimicrobial cationic polyacrylamide [31] active against S. epidermidis and was able to efficiently complex usnic acid (UA), a dibenzofuran natural extract known for its antimicrobial [32][33][34][35] and antiproliferative activities [36]. The use of UA in therapeutic application is rather limited due to its low water solubility [37] and toxicity issues [38,39].…”