## 3 Results
### Synergistic Effect of NS and \(\beta\)-Lactams with FIC Index Analysis  
The results presented in Table 2 are those of the FIC index interpretation that defines the time-kill assay synergistically for antibiotics and NS combinations. Combinations of 5.0 \(\upmu\)g/mL NS with antibiotics on MRSA 1 displayed synergism. The best effect was with AUG, while the worst was with OXA. Synergism was observed within 4 h on isolates that exhibited extensive resistance to antibiotics. In MRSA 4, a similar pattern was observed, except that synergistic effects were seen for AUG and CEF within 4 h, while with OXA, an additive effect was mostly displayed. For MRSA 5, the combination of NS with CEF had an additive effect compared with AUG and OXA, which displayed synergism within 8 h. Overall, the study with 5 \(\upmu\)g/mL combinations clearly indicates a synergistic effect.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Bacterial** \\ **Isolate/MRSA Type** \\ \end{tabular} } & \multirow{2}{*}{**Antibiotic Combination**} & \multicolumn{3}{c}{**Fractional Inhibitory Concentration Index**} & \\ \cline{3-5}  & & & **Time (h)** & & **Outcome** \\ \cline{2-5}  & & **2** & **4** & **8** & **12** \\ \hline MRSA 1 & NS + OXA & 0.4 & 0.5 & 0.7 & 0.7 & Synergism/Additive Effect \\ \hline  & NS + AUG & 0.3 & 0.5 & 0.6 & 0.5 & Synergism/Additive Effect \\ \hline  & NS + CEF & 0.4 & 0.5 & 0.7 & 0.6 & Synergism/Additive Effect \\ \hline MRSA 4 & & & & & & \\ \hline  & NS + OXA & 0.5 & 0.6 & 0.7 & 0.8 & Synergism/Additive Effect \\ \hline  & NS + AUG & 0.5 & 0.5 & 0.6 & 0.8 & Synergism/Additive Effect \\ \hline  & NS + CEF & 0.5 & 0.5 & 0.7 & 0.7 & Synergism/Additive Effect \\ \hline MRSA 5 & & & & & & \\ \hline  & NS + OXA & 0.5 & 0.5 & 0.5 & 0.8 & Synergism/Additive Effect \\ \hline  & NS + AUG & 0.5 & 0.5 & 0.5 & 0.7 & Synergism/Additive Effect \\ \hline  & NS + CEF & 0.7 & 0.6 & 0.6 & 0.7 & Additive Effect \\ \hline \hline \end{tabular}  
* NS = _Nigella sativa_, OXA = vacillin; AUG = augmentin; CEF = ceftroxine. The interaction was defined as synergistic if the FIC index was less than or equal to 0.5, additive if the FIC index was greater than 0.5 and less than or equal to 1.0, indifferent if the FIC index was greater than 1.0 and less than or equal to 2.0, and antagonistic if the FIC index was greater than 2.0.  
\end{table}
Table 2: Fractional inhibitory concentration index synergy interpretation of different MRSA isolates measured at time intervals for combinations of 5.0 \(\upmu\)g/mL _N. sativa_ and antibiotics.  
The synergistic time-kill assay, as interpreted with the FIC index for a 7.5 \(\upmu\)g/mL NS combination with antibiotics, is shown in Table 2. The combination of OXA, AUG, and CEF antibiotics all displayed synergism, with AUG and CEF exhibiting the best synergism up to 12 h. The pattern of synergistic effect on MRSA 4 was different, however. AUG had the best effect, but only for 4 h, which was then followed by additive effects. In MRSA 5, NS OXA combinations only produced additive effects. However, synergism was only observed for 2 h, as indicated in Table 2 for AUG and CEF combination. The overall FIC index ranged from 0.05 to 0.7, indicating synergism and additive effects.