Investigation of antibacterial activity and mechanism of T. spicata essential oil, and activation of the hydrosol formed as a by-product with UV

In this study, antibacterial activity of the essential oil (EO) and the hydrosol (HY) of Thymbra spicata L. were tested on K. pneumoniae and S. aureus . Since antimicrobial agent resistance is an important problem in infectious diseases, it was discussed the DRA (Dehydrogenase Relative Activity), DNA, and protein leakage during the inhibition period of bacteria exposed the EO. In addition, the effect of hydrosol interacted with UV on bacteria inoculated to artificial skin surface was studied. The main compounds of T. spicata EO were found as carvacrol (60.65%), γ-terpinene (23.03%), p-cymene (5.05%) by GC/MS (Gas Chromatography-Mass Spectrometry) analysis while HY’s main components were detected as carvacrol (91.23%) and thymol (5.43%). No antimicrobial effect of the hydrosol alone was observed for S. aureus and K. pneumoniae in this study. Inactivation of the bacteria by UV-activated hydrosol was performed on 1cm 2 -lab skin surface. The 0.02 CFU/cm 2 and 0.07 CFU/cm 2 log reductions were observed in K. pneumoniae at 5 and 15 minutes, respectively, while 0.6 CFU/cm 2 and 1.2 CFU/cm 2 log reductions were observed in S. aureus at 5 and 15 minutes, respectively, on the lab skin. The inhibition zones (IZ) of the EO were 34.32 mm and 10.02 mm for K. pneumoniae and for S. aureus, respectively. After treatment by T. spicata EO at MIC, the increase in the water-soluble proteins of bacteria exposed to the EO was between 0.57% and 0.6% for K. pneumoniae, 0.01% and 0.3% for S. aureus within 15 min . In S. aureus supernatant, DRA was between 67.32% and 66.4% within 15 min, while DRA dropped to 21% from 28.1% in K. pneumonia treated with the EO. The increase in DNA leakage of the bacteria exposed to the EO was 0.09%-0.12% for K. pneumoniae , 0.08%-0.1% for S. aureus within 15 min. The findings may have provided a broader perspective on working mechanisms of antibacterials and directed the industrial use of UV-activated hydrosol to become widespread.