Antibacterial and antibiofilm activity of essential oil of Achillea biebersteinii and its mode of action

Context: Microbial biofilms and antibiotic-resistant bacterial strains pose a challenge in clinical world as they fail to respond to conventional treatments. This failure of antibiotic treatment led researchers to look for alternatives. A possible alternative is plants derived essential oils. Many studies have reported that certain essential oils succeed where antibiotics fail. Aims: To test antibacterial and antibiofilm activities of essential oil of Achillea biebersteinii and its mode of action. Methods: Minimum biofilm inhibitory concentration (MBIC) susceptibility assays were performed using a biofilm inoculator with a 96-well plate with peg led. Minimum inhibitory concentration (MIC) was determined in normal microtitre plates using a twofold dilution series. Results: Achillea biebersteinii essential oil showed good activity against all tested bacteria. The MIC values were in the range of 0.125 - 1 mg/mL while MBIC values were in the range of 0.125 - 4 mg/mL. The mechanism of action of Achillea biebersteinii essential oil is related to a strong increase in membrane permeability of 260 nm absorbing materials and potassium ions from the cell membrane. Achillea biebersteinii essential oil was able to inhibit initial adherence of methicillin-resistant Staphylococcus aureus (ATCC 43300) at subinhibitory concentrations. Conclusions: Achillea biebersteinii essential oil has the potential for use as an effective antibacterial and antibiofilm agent that functions by impairing cell membrane permeability resulting in cellular death.