Application of mixture design for the optimum antibacterial action of chemically-analyzed essential oils and investigation of the antiadhesion ability of their optimal mixtures on 3D printing material

Contamination of food and medical devices has become a serious public health concern. Therefore, this work intended to assess the single and combined antibacterial effect of essential oils (EOs) obtained from Clinopodium nepeta, Ruta montana, and Dittrichia viscosa, through mixture design approach. In addition, the anti-adhesive action of the obtained optimal mixtures of EOs was investigated against bacterial adhesion on 3D printed surface, widely used in food and medical industries. Indeed, Chromatography Gas/Mass spectrometry (CG/MS) analysis showed that pulegone (30.2%), piperitenone oxide (15.71%), and limonene (10.32%), mainly characterized the Clinopodium nepeta essential oil (CNEO), whereas Ruta montana essential oil (RMEO) was dominated by 2-undecanone (46.13%), and 2-nonanone (20.53%). By contrast, the Dittrichia viscosa essential oil (DVEO) principally contained (E)-nerolidol (32.21%), τ-muurolol (18.17%), and α-eudesmol (10.36%). The obtained optimum mixtures revealed that the binary combination consisting of 36% of RMEO, 64% of CNEO certified the maximal inhibition against Staphylococcus aureus (S. aureus), while a formulation of 25%, 50%, and 25% of RMEO, CNEO, and DVEO respectively, was associated to the ideal restriction of Pseudomonas aeruginosa (P. aeruginosa). The time-kill analysis showed that all studied EOs are able to eradicate the total growth (bactericidal action) of S. aureus and P. aeruginosa at twice-minimal inhibitory concentration (2xMIC) after 12 h. Interestingly, the contact angle method and environmental scanning electron microscopy (ESEM) analysis reported that the optimal EOs mixtures are effective in preventing biofilm formation by modification of physico-chemical parameters of the 3D printing resin surface and complete inhibition of bacterial adhesion on the material surface. Thereby, the interaction between EOs might be applied as natural preservatives in the food and medical industries.