Antibacterial and anti-biofilm activity of nanoemulsion of Thymus daenensis oil against multi-drug resistant Acinetobacter baumannii

There is a growing interest in essential oil-based nanoemulsions, as an alternative antimicrobial compound for controlling multiple drug resistant (MDR) pathogens, such as Acinetobacter baumannii (A. baumannii). In this study, stable nanoemulsion was prepared from Thymus daenensis (T. daenensis) essential oil, and characterized in terms of physical stability, particle size, size distribution and shape, using dynamic light scattering (DLS) and transmission electron microscopy (TEM). Then, the antibacterial activity of the most stable preparation of nanoemulsion and pure oil was investigated, against 10 MDR A. baumannii isolates. In addition, anti-biofilm activity was analysed against selected MDR isolate (The number 40). The most stable nanoemulsion was produced with the particle size of 171.88 ± 1.57 nm, and spherical shape of nanoemulsion particles was confirmed by TEM images. The strong antibacterial activity of T. daenensis nanoemulsion and pure oil was revealed with MIC values of 30-45 μg/mL and 62.5-87.5 μg/mL, respectively. In addition, the nanoemulsion had considerable anti-biofilm activity on sub-lethal dose (56.43% inhibition in 1/2 MIC concentration), after 24 h of incubation. Presented data could help with the development of new therapeutically strategies for bacterial infections.