Abstract
The increasing incidence rate of oral diseases, the wide spread of antimicrobial resistance, and the adverse effects of conventional antibiotics mean alternative prevention and treatment options are needed to counteract oral pathogens. In this regard, our study aims to evaluate the antibacterial activity of polyphenolic extracts prepared from acacia honey, myrtle leaves, and pomegranate peel against cariogenic bacteria, such as Streptococcus mutans and Rothia dentocariosa. The chemical-physical parameters of acacia honey and the RP-HPLC polyphenolic profile of pomegranate peel extract have been previously described in our studies, while the characterization of myrtle extract, performed by HPLC analysis, is reported here. All the extracts were used singly and in binary combinations to highlight any synergistic effects. Moreover, the extracts were tested in association with amoxicillin to evaluate their ability to reduce the effective dose of this drug in vitro. The values of minimal inhibitory concentrations and minimal bactericidal concentrations have been used to quantitatively measure the antibacterial activity of the single extracts, while the fractional inhibitory concentration index has been considered as predictor of in vitro anticariogenic synergistic effects. Finally, a time-kill curve method allowed for the evaluation of the bactericidal efficacy of the combined extracts. The microbiological tests suggest that acacia honey, myrtle, and pomegranate extracts are able to inhibit the cariogenic bacteria, also with synergistic effects. This study provides useful and encouraging results for the use of natural extract combinations alone or in association with antibiotics (adjuvant therapy) as a valid alternative for the prevention and treatment of oral infectious diseases.
Highlights
Dysbiosis of oral microbiota, followed by the transition of several oral microorganisms from a commensal to pathogenic lifestyle, is a significant cause of dental caries (Nishikawara et al, 2007)
Time-Killing Assay With Binary Combination of Myrtle Leaves and Pomegranate Peel Polyphenolic Extracts To verify the inhibitory synergistic effect of the binary combination of pomegranate and myrtle polyphenolic extracts on the survival of S. mutans and R. dentocariosa, a time-killing assay was performed, which allowed for the investigation of the bactericidal efficacy of this antimicrobial combination over time
The polyphenol amount was found to be 15.75 mg gallic acid equivalents (GAE) g−1 for acacia honey extracts, 54.86 mg GAE g−1 for myrtle leaves extracts, and 45.9 mg GAE g−1 for pomegranate peel extracts
Summary
Dysbiosis of oral microbiota, followed by the transition of several oral microorganisms from a commensal to pathogenic lifestyle, is a significant cause of dental caries (Nishikawara et al, 2007). Tooth decay is a biofilm-mediated oral disease that causes several disturbances in adults and children. The pivotal role of this theory is represented by dietary carbohydrates, which are metabolized by plaque bacteria to produce acid end-products, resulting in a drastic reduction of microenvironmental pH. This process, if prolonged, could determine an acidification of environments which would result in a drastic dissolution of minerals from the tooth structure. Koch’s criteria, where an individual pathogen is implicated in a specific disease, are inapplicable to the polymicrobial biofilm-mediated caries disease (Caldwell et al, 1997; Sim et al, 2016). The bacteria associated with the caries disease have often been described as ‘opportunistic pathogens’; it has been suggested that since the bacteria implicated are resident bacteria, they should be described as pathobionts and not pathogens (Chow and Mazmanian, 2010; Ayres et al, 2012; Sim et al, 2016)
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