# In Vitro Activity of Caffe Acid Phenethyl Ester against Different Oral Microorganisms
## 3 Results  
Table 1 demonstrates the antibacterial potency of CAPE at various doses, in comparison to NaF mouthwash (positive control). The findings revealed that CAPE's antibacterial action was concentration-dependent, albeit only at low concentrations. _S. aureus_ had the greatest impact in preventing bacterial growth, followed by _S. salivarius_ and _S. oralis_, and _S. mutans_ had the least effect.  
To ensure consistency, the four bacterial strains colonies were counted. Following this, the identical CAPE dosages were applied, and cell-culture counts were used to calculate the MBC and MIC. With findings of 1 mg/mL and 1.5 mg/mL, respectively, the minimum concentration of CAPE required for the inhibition (MIC) or killing (MBC) of _S. mutans_ and _S. oralis_ was the most sensitive to CAPE. On the other hand, both _S. salivarius_ and _S. aureus_, were more resistant to CAPE, with MBC and MIC values of 4 mg/mL and 3 mg/mL, respectively. The NaF control exhibited slightly different antibacterial activity when compared to CAPE for the four cariogenic bacteria. The MIC for NaF was lower in the bacterial strains _S. salivarius_, _S. aureus_, and _S. oralis_, while it was higher for _S. mutans_ as compared to results of the MIC for CAPE. On the other hand, The MBC for NaF was lower in _S. aureus_, higher in _S. oralis_ and _S. mutans_, and similar in _S. salivarius_ as compared to results of the MBC for CAPE (Table 2).  
As seen in Figure 1, the viable count of the tested microorganisms after exposure to the MBC values of CAPE was the highest detected with _S. oralis_, followed by _S. salivarius_, and _S. mutans_ while the least detected was with _S. aureus_. The viable count of bacterial strains after exposure to the MBC concentrate of the CAPE was most effective after 12 h, where no bacterial growth was detected for all bacterial strains except for _S. aureus_. However, the results showed no bacterial growth for all different strains after 24 h. No difference was detected between the MBC values of CAPE and NaF among different strains after 24 h.  
\begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Concentration (mg/mL)**} & \multicolumn{4}{c}{**Inhibition Zone (Mean and SD in mm)**} \\ \cline{2-5}  & _S. mutans_ & _S. aureus_ & _S. salivarius_ & _S. oralis_ \\ \hline
**12.5** & 19 \(\pm\) 1.4 & 31 \(\pm\) 0.3 & 26 \(\pm\) 1.2 & 25 \(\pm\) 0.9 \\
**25** & 26 \(\pm\) 1.5 & 31 \(\pm\) 1.1 & 26 \(\pm\) 0.8 & 27 \(\pm\) 1.0 \\
**50** & 26 \(\pm\) 0.9 & 32 \(\pm\) 0.8 & 27 \(\pm\) 0.9 & 27 \(\pm\) 1.1 \\
**75** & 27 \(\pm\) 0.7 & 32 \(\pm\) 0.4 & 27 \(\pm\) 0.8 & 29 \(\pm\) 0.8 \\
**100** & 28 \(\pm\) 0.8 & 37 \(\pm\) 0.3 & 31 \(\pm\) 1.0 & 30 \(\pm\) 1.1 \\
**NaF** (+ve control) & 31 \(\pm\) 0.9 & 16 \(\pm\) 1.1 & 12 \(\pm\) 1.1 & 19 \(\pm\) 1.2 \\ \hline \end{tabular} Note: The diameter of the plate was 88 mm (44 mm = half diameter), which designates no bacteria growth.  
\end{table}
Table 1: Microbial inhibition zone in millimeters produced by the addition of CAPE at different concentrations compared to the NaF (positive control).  
\begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Microorganisms**} & \multicolumn{2}{c}{**CAPE**} & \multicolumn{2}{c}{**NaF**} \\ \cline{2-5}  & MIC & MBC & MIC & MBC \\ \hline _S. mutans_ & 1.0 & 1.5 & 1.86 & \textgreater{}3.0 \\ _S. salivarius_ & 3.0 & 4.0 & 0.93 & \textgreater{}4.0 \\ _S. oralis_ & 1.0 & 1.5 & 0.72 & \textgreater{}2.0 \\ _S. aureus_ & 3.0 & 4.0 & 0.74 & \textgreater{}2.0 \\ \hline \end{tabular}
\end{table}
Table 2: Bactericidal concentration and minimum inhibitory (mg/mL) of positive control NaF and CAPE against the four bacterial strains.  
The colony-forming units reflect the microorganisms' growth after exposure to the MIC concentrate; the CAPE was less potent against _S. salivarius_, _S oralis_, and _S. aureus_ compared to the control NaF. According to the Log10 transformation, only _S. mutans_ was significantly different from the control NaF (_p_ = 0.04).