Resumo

Introduction: Staphylococcus aureus and S. epidermidis are currently the main biofilm producer bacteria in clinical settings. Staphylococci multidrug resistance became common due to the antimicrobial irrational use, rising a demand of new antimicrobials. There are evidences of the antimicrobial activity of the cashew tree (Anacardium occidentale Linn.) stem bark hydro-ethanolic extract (SBHE), but few data is related to staphylococcal planktonic cells and there are few reports about its activity on bacterial biofilms. Objective: This study aimed to assess the antimicrobial activity of the SBHE on planktonic cells and biofilms of clinical isolates of 13 S. aureus and S. epidermidis strains. Methods: Broth macrodilution and microdilution assays were used as recommended by the Clinical and Laboratory Standards Institute in the determination of the minimal bactericidal concentration (MBC) of the SBHE against planktonic cells, biofilm formation and formed biofilms. Phytochemical analyses and fractions obtainment from cashew tree were conducted through C-18 column reversed phase chromatography and thin layer chromatography. Results: The MBC for planktonic cells was 30,54 mg/ml, and inhibition of biofilm formation and bactericidal effect on formed biofilms was seen at 61,09 mg/ml. Flavonoids, saponins, tannins and phenolic compounds were detected on the SBHE after thin layer chromatography. A synergic mechanism of action of the detected molecules for the whole antimicrobial potential of the SBHE is suggested, given that the same MBC was found for flavonoids, saponins and tannins fractions. Conclusions: Our findings indicate that the SBHE may contribute to anti-staphylococcal chemotherapy. Further investigation is being conducted for pharmaceutical purposes. Thanks to: FAPEMIG