In vitro Antibacterial Activity of Zingiber officinale and Orthosiphon stamineus on Enterococcus faecalis

This study evaluates the antibacterial effects of Zingiber officinale essential oil and Orthosiphon stamineus water extract against Enterococcus faecalis. The herbs were prepared in various concentrations to determine their minimum inhibitory concentrations (MIC) and growth inhibitory effect. Anti-adhesion activities of the herbs were determined by co-incubation with E. faecalis cultures for 6 and 24 h. Biofilm disruption activities were determined by adding the studied herbs into preformed E. faecalis biofilm. The effects on the morphology of E. faecalis grown as biofilm were studied using scanning electron microscopy (SEM). The MICs of ginger oil and O. stamineus extract were 0.31 and 25 mg/mL, respectively. Between the tested herbs, ginger exhibited greater inhibitory effects on the growth of E. faecalis grown in suspension mode. Both herbs generally showed anti-adhesion activities in inverse concentration-dependent manner. No significant biofilm disruption activities by both herbs were observed. SEM analyses showed E. faecalis cell surface changes in the treated biofilm. The studied herbs may have compromised the integrity of the bacterial cell membrane. These findings suggest that the studied herbs may have better antibacterial activities against E. faecalis in suspension mode compared to biofilm mode, with ginger oil showed greater antibacterial activity compared to O. stamineus extract.