In vitro activity of Quercus brantii extracts against biofilm- producing Pseudomonas aeruginosa

Background: Biofilm formation by Pseudomonas aeruginosa is a serious concern in treatment of diseases and medical industries. Natural products that originate in plants can influence microbial biofilm formation. The effect of ethyl acetate, methanol and water- methanol extracts of Quercus brantii on biofilm formation and biofilm disruption of P. aeruginosa were investigated in this study. Methods: The effect of Q. brantii extracts on biofilm formation ability of P. aeruginosa (ATCC 27853) and clinical isolates was tested using crystal violet (CV) staining assay. Minimum biofilm eradication concentration (MBEC) of the extracts against pre-formed biofilms alone and in combination with N-acetylcysteine (NAC) was also investigated. Results: Ethyl acetate extract of Q. brantii was the most effective extract and inhibited P. aeruginosa biofilm formation over 70%. It was followed by water-methanol extract (52% - 66% inhibition) and methanol extract (44% - 57% inhibition). Water-methanol extract of Q. brantii was more effective in eradication of P. aeruginosa pre-formed biofilms. The MBEC of Q. brantti extracts in combination with NAC was decreased in comparison to MBEC of Q. brantti extracts alone. Conclusion: This study demonstrated that Q. brantii extracts had a good inhibitory effect on biofilm formation ability of P. aeruginosa and could eradicate preformed-biofilms in combination with NAC.