Atividade de compostos fenólicos na inibição da formação de biofilme em Staphylococcus aureus

Abstract

Phenolic compounds are one of the major classes of secondary metabolites of plants and can be categorized into several classes, including phenolic acids, flavonoids and tannins. Several phenolic compounds have shown antimicrobial properties and capability to inhibit the biofilm formation by pathogenic bacteria, including Staphylococcus aureus. This study evaluated the efficacy of phenolic compounds in inhibiting biofilm formation of S. aureus. Flavonoids have been tested hesperetin, hesperidin, myricetin, myricitrin, phloretin, phloridzin and the tannins tannic acid. RN4220 and S. aureus AS-119B strains, which overexpress efflux protein genes were used as test strain. The S. aureus ATCC259233 strain which does not overexpress genes related to efflux proteins was used in tests. The minimum inhibitory concentration (MIC) of phenolic compounds was determined by the microdilution in broth method, while the minimum concentration for biofilm inhibition (MICB50) was determined by the microdilution in broth method with quantification of biofilm formation by absorbance at 595 nm. The tested phenolic compounds at 512 μg ml-1 showed no inhibitory activity on the growth of the strains tested; however, at lower concentrations showed inhibitory effects on biofilm formation by these same strains, the MBIC50 values varying between 1 to 256 μg ml-1, with lower values (1 and 2 μg ml-1) being observed against S. aureus RN-4220. Aglycone flavonoids showed lower MICB50 values than their respective glycone forms. Myricetin, hesperetin, phloretin and tannic acid exhibited biofilm formation inhibition > 70% for S. aureus RN- 4220. The results indicate that the tested phenolic compounds have the potential of inhibiting biofilm formation by S. aureus strains that overexpress efflux pumps.