Mode of Action and Antibacterial Activity of Ethanolic Ant Plant Tuber Extract Inhibiting Growth of Staphylococcus aureus and Escherichia coli

The present study aimed to investigate the activity of Hydnophytum formicarum Jack (Ant Plant) tuber extract against Staphylococcus aureus and Escherichia coli and the mode of action of the extract on bacterial responses. The antibacterial activity was determined using agar well diffusion method. Resazurin-based 96-well microdilution method was used to determine the Minimal Inhibitory Concentrations (MIC) of the extract. Mode of action on bacterial death and response patterns to the extract were assessed by flow cytometry using membrane integrity and granularity profiles. The results, based on serial dilution and zones of inhibition against the bacteria, showed that 2,000 µg/well was potent against S. aureus (16.33±1.53 mm) and E. coli (14.33±0.58 mm). For S. aureus, the MIC concentration was 8,000 µg/mL, while 4,000 µg/mL concentration exhibited activity against E. coli. Flow cytometric profiles confirmed loss of intracellular components, followed by death, for both bacteria. Bacterial responses to the extract had consistent dose- and time-dependent behavior. This is the first mode of action study on bacterial responses to H. formicarum tuber extract. The results suggest that the extract of H. formicarum tuber could serve as a source of an initial active ingredient for developing effective medicines to battle infections caused by pathogens. HIGHLIGHTS Ant plant tuber extract had a strong antibacterial activity against S. aureus and E. coli Intracellular component and bacterial membrane were the remarkable target for action of the extract Dose- and Time-response model for bacterial response to the extract was achieved using Flow cytometry