Trans-cinnamaldehyde potently kills Enterococcus faecalis biofilm cells and prevents biofilm recovery

Abstract

Enterococcus faecalis is a biofilm-forming, nosocomial pathogen that is frequently isolated from failed root canal treatments. Contemporary root canal disinfectants are ineffective in eliminating these biofilms and preventing reinfection. As a result, there is a pressing need to identify novel and safe antibiofilm molecules. The effect of short-term (5 and 15 min) and long-term (24 h) treatments of TC on the viability of E. faecalis biofilms was compared with currently used root canal disinfectants. Treatment for 15 min with TC reduced biofilm metabolic activity as effective as 1% sodium hypochlorite and 2% chlorhexidine. Treatment with TC for 24 h was significantly more effective than 2% chlorhexidine in reducing the viable cell counts of biofilms. This serendipitous effect of TC was sustained for 10 days under growthfavoring conditions. For the first time, our study highlights the strong antibacterial activity of TC against E. faecalis biofilms, and notably, its ability to prevent biofilm recovery after treatment.

Microbiological Aspects of Root Canal Infections and Disinfection Strategies: An Update Review on the Current Knowledge and Challenges

“…Tawakoli et al [ 113 ] characterized the effects of 5% sodium hypochlorite, 17% EDTA, 3% hydrogen peroxide, and 2% chlorhexidine on a three-species biofilm and reported that sodium hypochlorite eradicated the stainable matrix and bacteria in cultured biofilms, while chlorhexidine and hydrogen peroxide merely reduced bacterial cell volumes without dissolving the matrix [ 113 ]. Ali et al [ 114 ] demonstrated that a natural molecule trans-cinnamaldehyde could kill E. faecalis biofilm cells as effectively as sodium hypochlorite. Confocal microscopic characterization demonstrated largely “red” areas in the treated biofilm, implying complete bacterial killing [ 114 ].…”

“…Ali et al [ 114 ] demonstrated that a natural molecule trans-cinnamaldehyde could kill E. faecalis biofilm cells as effectively as sodium hypochlorite. Confocal microscopic characterization demonstrated largely “red” areas in the treated biofilm, implying complete bacterial killing [ 114 ]. However, when the same authors characterized the polysaccharide matrix component, they discovered that trans-cinnamaldehyde could not eliminate the matrix.…”

“…The authors of this review strongly recommend that when traditional or novel disinfectants are tested on biofilms, both the cellular and extracellular content of the biofilm must be studied to provide comprehensive information on anti-biofilm effects. Such characterization of the extracellular content maybe performed using biochemical methods [ 114 , 115 ] or by using matrix-component specific fluorophores for confocal microscopic imaging [ 37 ]. Furthermore, the use of multi-species as well as aged-biofilm models may better represent the biofilms found in infected root canals, which could enhance the applicability of in vitro research to the clinical situation.…”

“…The essential oil constituents, particularly eugenol, may be responsible for some of the antimicrobial properties of these herbal compounds [ 236 ]. Specifically, trans -cinnamaldehyde, a phenylpropanoid compound, commonly found in cinnamon, was recently reported to eradicate biofilm cells as potently as sodium hypochlorite and more importantly prevented repopulation of bacteria [ 114 ], in contrast to chlorhexidine which could not prevent biofilm recovery [ 138 ]. This is a significant finding as this is the first evidence that a natural molecule can kill biofilm cells and prevent reinfection with the same potency as sodium hypochlorite in clinically relevant time frames.…”

Antimicrobials from Medicinal Plants: An Emergent Strategy to Control Oral Biofilms

“…When used in the management of biofilms of S. mutans, the essential oil from C. zeylanicum skin was able to inhibit their formation by up to 99%, at a concentration of 0.224 mg•mL −1 [131]. β-linalool and (E)-cinnamaldehyde are the two main compounds present in this oil, and can be pointed out as responsible for its antibiofilm properties [132,133]. In addition, the essential oils of Coriandrum sativum L., a medicinal plant with nutritional benefits, commonly named coriander, exhibit antibacterial and antibiofilm properties against S. mutans, in addition to holding antioxidant and anesthetic properties [134,135].…”