Usnic Acid, a Natural Antimicrobial Agent Able To Inhibit Bacterial Biofilm Formation on Polymer Surfaces

Abstract

In modern medicine, artificial devices are used for repair or replacement of damaged parts of the body, delivery of drugs, and monitoring the status of critically ill patients. However, artificial surfaces are often susceptible to colonization by bacteria and fungi. Once microorganisms have adhered to the surface, they can form biofilms, resulting in highly resistant local or systemic infections. At this time, the evidence suggests that (؉)-usnic acid, a secondary lichen metabolite, possesses antimicrobial activity against a number of planktonic gram-positive bacteria, including Staphylococcus aureus, Enterococcus faecalis, and Enterococcus faecium. Since lichens are surface-attached communities that produce antibiotics, including usnic acid, to protect themselves from colonization by other bacteria, we hypothesized that the mode of action of usnic acid may be utilized in the control of medical biofilms. We loaded (؉)-usnic acid into modified polyurethane and quantitatively assessed the capacity of (؉)-usnic acid to control biofilm formation by either S. aureus or Pseudomonas aeruginosa under laminar flow conditions by using image analysis. (؉)-Usnic acid-loaded polymers did not inhibit the initial attachment of S. aureus cells, but killing the attached cells resulted in the inhibition of biofilm. Interestingly, although P. aeruginosa biofilms did form on the surface of (؉)-usnic acid-loaded polymer, the morphology of the biofilm was altered, possibly indicating that (؉)-usnic acid interfered with signaling pathways.

Secondary metabolic profiling and antibacterial activities of different species of Usnea collected in Northern Philippines

“…Lichens containing usnic acid have been used as crude drugs throughout the world (Ingólfsdóttir 2002). Interestingly, usnic acid is known to have activity against gram-positive bacteria, mycobacteria, VRE, and MRSA (Francolini et al 2004, Elo et al 2007). All of the 18 Usnea species in the study showed the presence of usnic acid (Fig.…”

“…The mechanism of this lichen substance is still unknown. However, studies have shown that its action may be due to its ability to inhibit RNA transcription (Francolini et al 2004). In addition, it was recently found that usnic acid plays an important role in the acidity tolerance of lichens and is an intrinsic cause of their SO 2 sensitivity (Hauck & Jürgens 2008).…”

Antibiofilm Activity of Epoxy/Ag-TiO2 Polymer Nanocomposite Coatings against Staphylococcus Aureus and Escherichia Coli

“…8-9 log in 30 min in case of P. aeruginosa. Francolini et al [19] evaluated the effect of (+)-usnic acid incorporated into modified polyurethane surfaces on the biofilm forming ability of S. aureus. After three days postinoculation, they found culturable biofilm cell concentration of S. aureus on the untreated polymer was 7.…”

“…The polycaprolactone-titania nanocomposites have been shown to decrease surface colonization of Escherichia coli and Staphylococcus aureus [18]. Similarly, introduction of (+)usnic acid, a natural antimicrobial agent into modified polyurethane prevented biofilm formation on the polymer surface by Staphylococcus aureus and Pseudomonas aeruginosa [19]. The poly(ethylene terephthalate) (PET) was surface functionalized with pyridinium groups possessing antibacterial properties, as shown by their effect on Escherichia coli [20].…”

Solid State Electrochemical Behavior of Usnic Acid at a Glassy Carbon Electrode

“…Many lichens and extracts containing UA have been extensively used in the medical, pharmaceutical, cosmetic, and agricultural fields. Actually, usnic acid exhibits a wide range of pharmacological properties (Rancan et al 2002;Dixon 2005;Francolini et al 2004;Fernández et al 2006): inhibition of the effects of viruses (Perry et al 1999) as well as of tumor promotion ; analgesic and antipyretic capacity (Okuyama et al 1995) and anti-inflammatory activity comparable to ibuprofen (Vijayakumar et al 2000) (for (þ) UA); antifungal activity against some plant pathogens (Proksa et al 1996); antiherbivore and anti-insect effects (Romagni et al 2000;Emmerich et al 1993) (for (À) UA). Other characteristics of UA are ultraviolet absorption and preservation properties.…”