## 3 Results  
### In Vitro Antibacterial Effect of Plant Extracts  
#### 3.1.1 Disc-Diffusion Assay  
Results revealed that 10 methanol plant extracts displayed different potent activities against an array of Gram positive and Gram negative bacteria (Table 2), of which, _Camellia sinensis_, _Aloysia citroroda_, _Hibiscus sabdariffa_, _Thymus vulgaris_, _Phomis brachyodon_, _Anchusa azurea_ and _Glycyrrhiza glab_ showed the highest antibacterial activity against MRSA isolates with an inhibition zone of 19.9, 19.3, 14.7, 14.5, 13.9, and 13.1 mm, respectively. _Aloysia citroda_, _Camellia sinensis_, _Glycyrrhiza glab_, _Hibiscus sabdariffa_, _Thymus vulgaris_, _Phomis brachyodon_, and _Anchusa azurea_ showed antibacterial activity against MSSA isolates with an inhibition zone of 20, 19.5, 15.4, 14.6, 14.3, 14.2, and 13.1 mm, respectively. _E. coli_ were affected by _Phomis brachyodon_ (16.4 mm), _Palenis spinosa_ (13.9 mm), _Urtica pillifera_ and _Anchusa azurea_ (12.4 mm) and _Hibiscus sabdariffa_ (11.5 mm) while _P. aeruginosa_ was not affected by any of the extracts except _Hibiscus sabdariffa_ zone of inhibition (12 mm). Results of the antimicrobial activity of the tested plant extracts showed that _P. aeruginosa_ was the most resistant isolate, followed by _E. coli. Camellia sinensis_ and _Aloysia citroda_ showed the best antibacterial effects against _S. aureus_.  
.1.2 Minimum Inhibitory Concentration Assay (MIC) and Minimum Bactericidal Concentration Assay (MBC)  
Five of the most effective plant extracts; _Camellia sinensis_; _Aloysia citroda_; _Hibiscus sabdariffa_, _Glycyrrhiza glab_, and _Thymus vulgaris_ were tested by MIC and MBC against _S. aureus_, _E. coli_, and _P. aeruginosa_. Plant extracts that showed a zone of inhibition \(\geq\)14 mm in disc diffusion test were tested by microdilution assay. Gentamycin and vancomycin were used as positive controls. Ten isolates for each of MRSA, MSSA and _E. coli_ and five isolates of _P. aeruginosa_ were tested. Results are presented in Table 3. Among the three bacterial species, the _Camellia sinensis_ extract showed the highest antibacterial activity  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & & & **Antibacterial Activity (Zone of Inhibition, mm)** & & & & \\ \hline
**Plants** & **MRSA** & **MRSA** & **MSSA** & **MSSA** & **P.A.** & **P.A.** & _E. coli_ & _E. coli_ \\
**(10 mg/disc)** & **ATCC 43300** & **Isolates** & **ATCC 25923** & **Isolates** & **ATCC 0927** & **Isolates** & **NTCC 0157** & **Isolates** \\ \hline _Camellia sinensis_ & 22 & 19.9 & 23 & 19.5 & 9 & 8.5 & 0 & 0 \\ _Aloysia citroda_ & 21 & 19.3 & 18 & 20 & 9 & 9.3 & 10 & 8.9 \\ _Hibiscus sabdariffa_ & 15 & 14.7 & 15 & 14.6 & 12 & 12 & 11 & 11.5 \\ _Glycyrrhiza glab_ & 13 & 13.1 & 15 & 15.4 & 0 & 0 & 0 & 0 \\ _Phomis brachyodon_ & 13 & 14.5 & 14 & 14.2 & 10 & 9.6 & 16 & 15.4 \\ _Thymus vulgaris_ & 15 & 14.5 & 15 & 14.3 & 0 & 0 & 0 & 0 \\ _Ultria Pilifera_ & 8 & 8.7 & 8 & 8.2 & 9 & 9.7 & 13 & 12.4 \\ _Anchusa azurea_ & 13.4 & 13.9 & 14 & 13.1 & 0 & 0 & 12 & 12.4 \\ _Planting Innovative_ & 12 & 12.3 & 12 & 12.5 & 0 & 0 & 0 & 0 \\ _Pallensis spinosa_ & 0 & 0 & 0 & 0 & 8 & 8.4 & 13 & 13.9 \\ _Vancomycin_ (30) & 20 (S) & 18 (S) & 21 (S) & 20 (S) & NT & NT & NT & NT \\ Gentamycin_ & 26 (S) & 25 (S) & 28 (S) & 24 (S) & 20 (S) & 18 (S) & 25 (S) & 22 (S) \\ \hline \hline \end{tabular} Values of zones of inhibition are the mean of 10 tested MRSA, MSSA and _E. coli_ isolates and five _P. aeruginosa_ isolates. NT: Not tested; P.A: _P. aeruginosa_; R: resistant; S: susceptible.  
\end{table}
Table 2: Antibacterial activities of plant extracts against the tested bacteria.  
against _S. aureus_ (MRSA and MSSA) with a MIC value (0.5 mg/mL). Extracts of _Camellia sinensis_ and _Aloysia citrodota_ displayed wide spectra of antibacterial activity in comparison to other plants. _E. coli_ and _P. aeruginosa_ showed the highest resistance profile in comparison to _S. aureus_.