Antimicrobial properties of Thymus vulgaris, Origanum majorana and Ziziphora clinopodioides combined essential oils and their effects on growth behavior of Aeromonas hydrophila

This study aimed to determine the chemical composition of Thymus vulgaris , Origanum majorana and Ziziphora clinopodioides and evaluate the antimicrobial properties of their combined essential oils i.e. T.o.z 50% T.v, 25% O.m and 25% Z.c; t.O.z = 25% T.v, 50% O.m and 25% Z.c and t.o.Z = 25% T.v, 25% O.m and 50% Z.c, against Aeromonas Hydrophila (in vitro). The compositions of the herbal essential oils were determined using gas chromatography–mass spectrometry (GC-MS) and the antimicrobial effects was conducted using agar-disc diffusion method, determination of MIC and MBC, and bacterial growth curves determination based on OD at 600 nm. The main compounds were Thymol (40.60%) and Limonene (15.98%) for T. vulgaris , Carvacrol (57.86%) and Thymol (13.54%) as the major compounds in O. magorana . Regarding Z. clinopodiodes , α-pinene (22.6%) and Carvacrol (21.1%) represented the major constituents. Base on the disc-diffusion results, t.O.z showed the best inhibition zone (26 mm). The inhibitory activity and bactericidal effect of t.O.z, unveiled by the MIC and MBC values, was clearly the highest between all combined herbal oils. Regarding the bacterial growth curves, the combined essential oils exhibited significant differences in all tested concentrations. The t.O.z was the most effective between the three tested combined oils at different temperature that cannot affect herbal oil performance. As conclusion, we suggested that the mixing of herbal oils with growth media was delaying exponential phase starting in the bacterial growth curves.