Abstract
BackgroundA number of oral diseases, including periodontitis, derive from microbial biofilms and are associated with increased antimicrobial resistance. Despite the widespread use of mouthwashes being used as adjunctive measures to control these biofilms, their prolonged use is not recommended due to various side effects. Therefore, alternative broad-spectrum antimicrobials that minimise these effects are highly sought after. Carbohydrate derived fulvic acid (CHD-FA) is an organic acid which has previously demonstrated to be microbiocidal against Candida albicans biofilms, therefore, the aims of this study were to evaluate the antibacterial activity of CHD-FA against orally derived biofilms and to investigate adjunctive biological effects.MethodsMinimum inhibitory concentrations were evaluated for CHD-FA and chlorhexidine (CHX) against a range of oral bacteria using standardised microdilution testing for planktonic and sessile. Scanning electron microscopy was also employed to visualise changes in oral biofilms after antimicrobial treatment. Cytotoxicity of these compounds was assessed against oral epithelial cells, and the effect of CHD-FA on host inflammatory markers was assessed by measuring mRNA and protein expression.ResultsCHD-FA was highly active against all of the oral bacteria tested, including Porphyromonas gingivalis, with a sessile minimum inhibitory concentration of 0.5%. This concentration was shown to kill multi-species biofilms by approximately 90%, levels comparable to that of chlorhexidine (CHX). In a mammalian cell culture model, pretreatment of epithelial cells with buffered CHD-FA was shown to significantly down-regulate key inflammatory mediators, including interleukin-8 (IL-8), after stimulation with a multi-species biofilm.ConclusionsOverall, CHD-FA was shown to possess broad-spectrum antibacterial activity, with a supplementary function of being able to down-regulate inflammation. These properties offer an attractive spectrum of function from a naturally derived compound, which could be used as an alternative topical treatment strategy for oral biofilm diseases. Further studies in vitro and in vivo are required to determine the precise mechanism by which CHD-FA modulates the host immune response.
Highlights
A number of oral diseases, including periodontitis, derive from microbial biofilms and are associated with increased antimicrobial resistance
We report that Carbohydrate derived fulvic acid (CHD-FA) displays rapid microbiocidal activity against orally relevant biofilms, and that it is able to down-regulate the expression of proinflammatory molecules in orally relevant epithelial cells
CHD-FA showed a rapid rate of kill for the periodontal pathogens tested as polymicrobial biofilms, as after 30 min treatment cellular viability was reduced by ≥90%, which was observed for studies of C. albicans [15]
Summary
A number of oral diseases, including periodontitis, derive from microbial biofilms and are associated with increased antimicrobial resistance. Biofilms are of greater clinical importance than their free-floating planktonic counterparts because of their innate ability to resist antimicrobial therapy and host defences. This is due to the extensive ECM production and other factors such as increased extrusion of antimicrobials through enhanced efflux pump activity [3,4]. Antimicrobial mouthwashes are one of the main therapeutic and preventative strategies currently used in the management of oral biofilm diseases, of which chlorhexidine (CHX) is widely accepted as the ‘gold standard’ [5]. It has been shown recently to be ineffective against biofilms grown from clinical isolates [10]
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