## 3 Results and Discussion  
### Inhibition of Nanoparticles of Garlic Extract on the Different Bacteria  
The antibacterial activity of the nanoparticles of the ultrasonicated extract was assessed against two strains of gram-positive bacteria (_S. mutans_ and _S. aureus_ sub. _aureus_) and two strains of gram-negative bacteria (_E. coli_ and _P. gingivalis_) by using both the agar disk diffusion and agar well diffusion methods. The diameters of the inhibition zones were determined, and the results are illustrated in Figure 1 and Tables 1-4. Garlic extracts have also been reported to be effective against both gram-positive and -negative bacteria such as _Bacillus cereus_, _Escherichia coli_, _Enterobacter cloace_, _Klebsiella pneumoniae_, _Microoccus flavus_, _Proteus mirabilis_, _Pseudomonas aeruginosa_, _Salmonella typhi_, _Salmonella typhiurium_, and _Staphylococcus aureus_[31; 32; 33; 34]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Garlic Extract** \\ **(mg/mL)** \\ \end{tabular} } & \multicolumn{3}{c}{**Inhibition Zone (mm)**} \\ \cline{2-5}  & _S. mutans_ & _S. aureus_ & _E. coli_ & _P. gingivalis_ \\ \hline
5 & 0.0 \(\pm\) 0.0 g & 0.0 \(\pm\) 0.0 d & 0.0 \(\pm\) 0.0 f & 0.0 \(\pm\) 0.0 g \\ \hline
10 & 0.0 \(\pm\) 0.0 g & 0.0 \(\pm\) 0.0 d & 0.0 \(\pm\) 0.0 f & 0.0 \(\pm\) 0.0 g \\ \hline
20 & 12.1 \(\pm\) 0.7 f & 0.0 \(\pm\) 0.0 d & 0.0 \(\pm\) 0.0 f & 11.2 \(\pm\) f \\ \hline
40 & 20.2 \(\pm\) 0.6 e & 15.7 \(\pm\) 0.6 c & 14.2 \(\pm\) 0.8 e & 19.3 \(\pm\) e \\ \hline
60 & 22.2 \(\pm\) 1.0 d & 16.0 \(\pm\) 1.0 c & 15.3 \(\pm\) 0.6 d & 21.5 \(\pm\) d \\ \hline
80 & 24.2 \(\pm\) 0.7 c & 18.1 \(\pm\) 0.9 b & 16.4 \(\pm\) 0.5 c & 23.2 \(\pm\) c \\ \hline
100 & 26.2 \(\pm\) 0.8 b & 19.1 \(\pm\) 1.0 b & 17.4 \(\pm\) 0.5 b & 25.3 \(\pm\) b \\ \hline Standard & 33.0 \(\pm\) 0.0 a & 26.3 \(\pm\) 0.0 a & 24.1 \(\pm\) 0.0 a & 31.9 \(\pm\) 0.0 a \\ \hline R-Square & 0.9982 & 0.9922 & 0.9985 & 0.9989 \\ \hline Coeff Var & 3.41 & 8.84 & 3.91 & 2.71 \\ \hline Root MSE & 0.59 & 1.05 & 0.43 & 0.45 \\ \hline \hline \end{tabular} Values are the mean \(\pm\) standard deviation (S.D.) of three replicates. According to [PERSON]’s multiple range test, S.D. within a column followed by different letters are significantly different at \(p\leq\) 0.05 level. Coeff Var: coefficient of variation; Root MSE: Root-mean-square deviation.  
\end{table} 
Table 1: Antibacterial activity of nanoparticles (supernatant) of garlic extract against _S. mutans_, _S. aureus_ sub. _aureus_, _E. coli_, and _P. gingivalis_ by agar disk diffusion method. The results show that different bacteria species exhibited different sensitivities against the ultrasonicated garlic extract at different concentrations of 5, 10, 20, 40, 80, and 100 mg/mL. The highest inhibition was observed against _S. mutans_ at concentrations of 100 mg/mL of garlic nanoparticles and showed the zone of inhibition of 26.2 \(\pm\) 0.8 mm by agar disk diffusion (Table 1) and 28.7 \(\pm\) 0.9 mm by agar well diffusion method (Table 2), which is the greatest inhibition among all tested strains. _P. gingivalis_ was ranked as the second most susceptible, followed by _S. aureus_ sub. _Aureus_, and then _E.coli_ was the bacteria to be least inhibited by nanoparticles from garlic extract in both the well and disk diffusion methods. Several studies have shown that garlic extracts possess an intense antibacterial activity