Peerapas Weerakiet¹, Montree Udompataikul¹, Malai Taweechotipatr²

Background: Because of the growing use of antibiotics worldwide, the expansion of antibiotic-resistant bacteria becomes increasingly threatening to medical treatment. Many natural substances have been reported to have antimicrobial properties.

Objective: To evaluate the antimicrobial property and the synergistic interaction between potassium aluminum sulfate and Phyllanthus emblica leaves against common skin pathogens, including antibiotic-resistant Cutibacterium acnes, antibiotic-susceptible C. acnes, Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus luteus, Pseudomonas aeruginosa, and Candida albicans.

Materials and Methods: The present study was an experimental, cross-sectional study. The microorganisms were tested using the agar well diffusion method and the broth microdilution method to determine the minimum inhibitory zone (MIZ) and minimum inhibitory concentration (MIC), respectively. Finally, the synergistic interaction was evaluated by checkerboard assay to determine the fractional inhibitory concentration (FIC) index.

Results: The highest inhibition zone, at 21 mm, was observed on P. aeruginosa with the alum concentration of 20% w/v. The lowest inhibition zone, at 6 mm, was noticed on S. aureus with 2.5% concentration of alum. P. emblica extract at a concentration of 5 mg/mL and 25 mg/mL demonstrated antimicrobial activity against S. aureus, S. epidermidis, M. luteus, and C. acnes. The lowest MIC of alum solution (0.0195% w/v) was seen on S. epidermidis. The lowest MIC of P. emblica extract, at 0.097 mg/mL, was spotted on C. acnes. The highest FIC index, of 0.421, was observed on M. luteus and the lowest FIC index, at 0.046, was seen on S. aureus.

Conclusion: Both alum and P. emblica leaves exhibited substantial antimicrobial activity and can be combined for enhanced efficacy.

Received 26 July 2024 | Revised 11 November 2024 | Accepted 20 November 2024

DOI: 10.35755/jmedassocthai.2025.1.58-64-01385