Carbohydrate Derived Fulvic Acid: An in vitro Investigation of a Novel Membrane Active Antiseptic Agent Against Candida albicans Biofilms

Abstract

Carbohydrate derived fulvic acid (CHD-FA) is a heat stable low molecular weight, water soluble, cationic, colloidal material with proposed therapeutic properties. The aim of this study was to evaluate the antifungal activity of CHD-FA against Candida albicans, and to characterize its mode of action. A panel of C. albicans isolates (n = 50) derived from a range of clinical specimens were grown planktonically and as biofilms, and the minimum inhibitory concentrations determined. Scanning electron microscopy was performed to examine ultrastructural changes and different cell membrane assays were used to determine its mode of action. In addition, the role of C. albicans biofilm resistance mechanisms were investigated to determine their effects on CHD-FA activity. CHD-FA was active against planktonic and sessile C. albicans at concentrations 0.125 and 0.25% respectively, and was shown to be fungicidal, acting through disruption of the cell membrane activity. Resistance mechanisms, including matrix, efflux, and stress, had a limited role upon CHD-FA activity. Overall, based on the promising in vitro spectrum of activity and minimal biofilm resistance of the natural and cheap antiseptic CHD-FA, further studies are required to determine its applicability for clinical use.

A Combination Fluorescence Assay Demonstrates Increased Efflux Pump Activity as a Resistance Mechanism in Azole-Resistant Vaginal Candida albicans Isolates

“…The Ala-Nap efflux assay was performed using a previously published protocol (24,25). Briefly, 100 l of starved cells was added to a blank 96-well plate (a Corning Costar 96-well black plate; Fisher Scientific).…”

“…Recently, a bacterial assay for generalized efflux that uses the fluorescence molecule alanine ␤-naphthylamide (Ala-Nap) (23) has been applied to Aspergillus fumigatus and C. albicans (24,25). No oral or systematic clinical isolates have been studied with Ala-Nap.…”

Effect of essential oils prepared from Thai culinary herbs on sessile <i>Candida albicans</i> cultures

“…These findings have reiterated the fact that sessile fungal cultures are more resistant to several antifungal agents (either synthetic or naturally-derived) than planktonic cultures (7,29,30). Many intrinsic properties of fungal biofilms such as low metabolic activity, contact-induced gene expression, presence of extracellular matrix, persister cells, and high anti-oxidative capacities exhibit major involvement in its resistance to the administrated antifungal agents (16).…”

“…All infections are closely associated with the biofilm formation of Candida species (6). The community structure of these yeast cells have well-regulated metabolic processes and inter-organism communication, and act as a robust shelter that protects the interior organisms from antifungal drug attacks (7). The biofilm formed has been shown to be refractory (less susceptible) to several antifungal drugs, such as azoles (fluconazole, ketoconazole, and miconazole), polyenes (amphotericin B, nystatin, and natamycin), and echinicandins (caspofungin, micafungin, and anidulafungin), which are commonly employed as prophylactic and therapeutic agents against candidal infections (8,9).…”

Antimicrobial compounds from natural sources

“…Not to mention the interesting and unusual sources such as coal or lignite, which may provide future antimicrobial compounds candidates. The recent development of a patented process to GMP standards (PA107470/GB), rendering the obtainment of carbohydrate derived fulvic acid (CHD-FA), stimulated Sherry et al (2012) to study and describe for the first time a highly effective novel antiseptic effect of fulvic acid with exquisite biofilm activity that acts by disrupting cell membranes. The antifungic peptide from Amazonian Pink Toe spider Juruin, described by Ayroza et al (2012) is another outstanding example of the potential contribution of a systematic exploration of nature aiming to provide additional antimicrobial leads and drugs.…”