## 2 Results and Discussion
### Antibacterial Activity of Essential Oil  
The antibiotic resistance of strains used in the present work was well investigated before testing. All selected strains were found to be resistant to a large category of drugs, as shown in Table 3.  
In the present work, five concentrations of essential oil were used to evaluate the antibacterial activity using the agar diffusion method and minimum inhibitory concentration (MICs) assays. The results obtained are presented in Tables 4 and 5. The results summarized in Tables 4 and 5 show that the oil possesses a potent inhibitory effect on all selected bacteria, either Gram-negative or Gram-positive strains with different inhibition zone diameters. _E. coli_ and _S. aureus_ were the most sensitive bacteria to EO with inhibition zone diameters of 27 mm and 26 mm, respectively. The obtained results also revealed that the hydrolat was effective on _E. coli 57_, _K. pneumoniae_, _P. aeruginosa_, and _S. aureus_ except _E. coli 97_. A microdilution method was used to determine the minimal inhibitory concentration of the test sample (Table 5). The results obtained showed that the lowest inhibitory concentration of OE was recorded for _P. aeruginosa_ with a concentration of 1/640 mg/mL, followed by _K. pneumoniae_ with 1/320 mg/mL. Moreover, the studied OE was shown to be effective versus both types of Gram-positive and Gram-negative bacteria, unlike streptomycin and ampicillin, which were less effective [38]. Overall, the best antibacterial effect was shown by the EO vs. the broad spectrum of bacteria including both Gram-negative (_E. coli 57_, _E. coli 97_, _K. pneumoniae_, _S. aureus_) and Gram-positive bacteria (_P. aeruginosa_). The antibacterial properties of essential oils observed in this work can be explained by the fact that the oil has a lipophilic character that makes it easy to penetrate the bacteria cell and ultimately lead to bacteria death. It was reported that the hydrocarbons make essential oil preferentially lodged in the biological membranes, which disturbs the membrane permeability, and ultimately leads to the immediate death of bacteria [38; 39; 40]. Closer data reported on the mechanism of action of oils with hydrocarbons can serve as a valuable reference for a better understating of oil  
Figure 4: The absorbance of \(\beta\)-carotene in the presence of the samples studied, BHT, and control. \begin{table}
\begin{tabular}{c c} \hline \hline
**Bacterial Strains** & **Drug Resistance** \\ \hline _Klebsiella pneumoniae_ & AMX, CAZ, K \\ _Escherichia coli_ & CXM, AMX, CTX, K, SXT and CIP \\ _Pseudomonas aeruginosa_ & SXT et AMC \\ _Staphylococcus aureus_ & VA \\ \hline \hline \end{tabular}
\end{table} 
Table 3: List of drug resistance applied to the studied bacteria. bacteria [41]. Chemicals in the oil can work in synergy more than individually, as previous work showed that the antimicrobial activity of essential oils was found to be higher than its single compounds tested separately [42; 43]. Our findings showed that the bacterial strains tested whether Gram-negative or whether Gram-positive was found to be completely resistant to Ampicillin and partially to Streptomycin. These results agree with those reported in earlier works [44], which showed that the most threatening drug-resistant microbes including _S. aureus_, _K. pneumoniae_, _A. buumanini_, _P. aeruginosa_, _Enterobacter_ spp., and _E. coli_ pathogens. The microbes tested in this work are classified as being multidrug-resistant, extensive drug-resistant, and even pan-drug-resistant, as reported elsewhere [15; 16]. The limited treatment strategies vs. drug-resistant infections require new and more effective antibiotics, however, the number of antibiotics approved for clinical use since 2000 has been limited and most of them respond only to Gram-positive bacteria, and their response against Gram-negative strains are reduced by the time, which can accentuate the emergence of a greater threat to human health [45; 46].