IN VITRO ACTION OF PLANT EXTRACTS ON ENTEROCOCCUS FAECALIS

Abstract

Enterococci faecalis plays a significant role in diseases in clinical dental practice, especially as a causative agent of endodontic and soft tissue infections. The constituents of medicinal plants can be used in association with medicines, as raw material, or directly as pharmacologically active compounds and offer an alternative or adjuvant in antimicrobial treatment, and can be a useful resource in dentistry. The aim of the present study was to evaluate the inhibitory potential and interaction with amoxicillin of medicinal plant extracts on E. faecalis. Two strains of E. faecalis, ATCC 29.212 and ATCC 51.299, were used to determine the percentage of bacterial growth inhibition, interaction of antimicrobials with plant extract, and action on biofilm formation. The ethanolic extracts of Lantana camara, Lippia macrophyla, Genipa americana, and hexane extracts of Hypericum connatum and H. caprifoliatum were used in concentrations ranging from 31.1 to 1000 μg/mL. For the tests of interaction between plant extract and amoxicillin, the checkerboard method was used with concentrations of L. camara extract from 16 to 1000 μg/mL and amoxicillin from 0.16 to 10 μg/mL. To verify the action on biofilm formation, the violet crystal method was used. All the extracts tested inhibited the growth of E. faecalis varying according to strain and extract. For the ATCC 29.212 strain, all extracts presented results significantly lower than the mean value of chloramphenicol and, at the concentration of 500 μg/mL of the extracts, comparable to the mean value of amoxicillin. For ATCC strain 51,299, no extract demonstrated action comparable to chloramphenicol or amoxicillin. Regarding the action on the formation of the biofilm, it was observed that the extract of L. camara at a concentration of 1000 μg/mL does not interfere with the action of amoxicillin. It is concluded, therefore, that extracts of plant species of the Verbenaceae, Hypericaceae and Rubiaceae families are promising as inhibitors of E. faecalis growth in vitro, and further research is recommended to establish whether or not these extracts are effective in their clinical application in the search for alternative treatments in oral disease.