## 3 Results and Discussion
### Antimicrobial Activities of the Essential Oils
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Microbial Strain/Essential Oils**} & \multicolumn{4}{c}{**MIC Values [\% Dilution in Microbial Culture Media]**} \\ \cline{2-6}  & **FEN** & **SV** & **EUC** & **CI** & **PIN** \\  & **(Fennel EO)** & **(Sage EO)** & **(Eucalyptus EO)** & **(Thyme EO)** & **(Pine EO)** \\ \hline _Staphylococcus aureus_ ATCC 25923 & 5\% & 2.5\% & 2.5\% & 1.25\% & 10\% \\ \hline _Pseudomonas aeruginosa_ ATCC 27853 & 5\% & 1.25\% & 2.5\% & 1.25\% & 10\% \\ \hline _Escherichia coli_ ATCC 25922 & 5\% & 0.156\% & 1.25\% & 0.625\% & 10\% \\ \hline _Candida albicans_ ATCC 10231 & 10\% & 1.25\% & 2.5\% & 2.5\% & 10\% \\ \hline \hline \end{tabular}
\end{table} 
Table 6: MIC values were obtained by the method of serial micro dilutions in a liquid environment. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Essential**} & \multicolumn{4}{c}{**Inhibition Zones [mm]**} \\ \cline{2-5}  & _Escherichia coli_ & _Staphylococcus aureus_ & _Pseudomonas aeruginosa_ & _Candida albicans_ \\  & **ATCC 25922** & **ATCC 25923** & **ATCC 27853** & **ATCC 10231** \\ \hline \multicolumn{1}{c}{**Fennel EO (FEN)**} & 16 & 14 & 14 & 0 \\ \hline \multicolumn{1}{c}{**Sage EO (SV)**} & 22 & 12 & 19 & 0 \\ \hline \multicolumn{1}{c}{**Eucalyptus EO (EUC)**} & 15 & 6 & 11 & 0 \\ \hline \multicolumn{1}{c}{**Thyme EO (CI)**} & 30 & 30 & 27 & 35 \\ \hline \multicolumn{1}{c}{**Pine EO (PIN)**} & 15 & 0 & 12 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Inhibition zones of essential oils (dil. 1/10 in DMSO). Several studies show that many of the essential oils tested have an antibacterial effect on the _Escherichia coli_ strain. For example, Xiao and contributors [100] tested the inhibitory effect of 140 commercial essential oils on _Escherichia coli_ by determining the MIC values and found that 8 of them, including oregano oil, cloves, and cinnamon, have a stronger antimicrobial effect on _Escherichia coli_ strain compared to sufloxacin antibiotic. Also, 40 of the tested essential oils, including cinnamon oil, tea tree oil, and thyme oil, had values of the minimum inhibitory concentration between 0.5-0.125%, and for oregano essential oil, the minimum inhibitory concentration was 0.015% [100]. Contrary to the results of the qualitative tests, the fennel essential oil did not show low MIC values, probably due to its low solubility in the liquid environment, the MIC values being among the highest (5-10%). _Study of the influence of the tested compounds on the development of microbial biofilms on the inert substratum_. Testing the properties of essential oils to inhibit the adhesion of microbial cells to the inert substrate and to generate monospecific biofilms allowed the establishment of the values of the Minimum Concentration of Biofilm Eradication (MCBE). These values are represented by the highest oil dilutions that inhibited adhesion and are represented in the graphs below (Figures 8-11). For the most essential oils tested in this study, the MCBE values are close to the MIC values, except the pine EO which seems to have stimulated the adhesion of the yeast strain at concentrations lower than 5% (Figure 10). For _Escherichia coli_ ATCC 25922 strain the lowest values of the MCBE were recorded for sage EO (0.04%). _Staphylococcus aureus_ is one of the pathogens that cause most of the recurrent infections associated with biofilm production. In this paper, the lowest values of MCBE for _Staphylococcus aureus_ ATCC 25923 were observed in the case of sage and thyme essential oils (SV, CI). Also, a study by Sharifi et al. [101] highlighted the ability of thyme essential oil to eradicate the biofilm produced by _Staphylococcus aureus_ isolated from the respiratory tract and from milk samples.