Do ethanolic extracts of Lamiaceae species used in folk medicine have antibiofilm activity on Pseudomonas aeruginosa PAO1?

Abstract

BACKGROUND According to World Health Organization, 70-95% of the population chooses folk medicine as their primary approach for health maintenance. In addition to their healing properties and application in folk medicine, Lamiaceae plants are often valued in cookery as spices and food preservatives. OBJECTIVES Hence, the aim of this study was to examine the antibiofilm activity of 12 ethanolic extracts of Lamiaceae species on biofilm formation and the degradation of existing biofilm of Pseudomonas aeruginosa PAO1 (ATCC 15692). METHODS The crystal violet staining method was used to evaluate the newly formed bacterial biofilms. Four concentrations (double dilutions) of plant extracts (starting conc. 2500 μg/mL), solvent control (ethanol, starting conc.15%), and positive control (streptomycin, starting conc. 12.5 μg/mL) were tested. RESULTS All ethanol extracts showed antibiofilm activity. However, the strongest activity was observed for Hyssopus officinalis, Melissa officinalis, Mentha piperita, and Ocimum basilicum, where the viability of bacteria in the biofilm after treatment was about 60% mainly at each tested concentration. Teucrium chamaedrys extract exhibited the strongest activity by degrading about 60% of biofilm (about 40% viability) at all concentrations except at the lowest tested one. Promising results were also observed for M. piperita (at each of the tested concentrations) and O. basilicum (at the highest tested concentration), where the viability of bacteria in the biofilm after treatment was reduced by about 40%. The remaining extracts showed a slightly lower effect on the degradation of the previously formed biofilm of P. aeruginosa PAO1.