Background: Kheaw-Hom is a Thai traditional remedy which appears in the National List of Essential Medicines 2011. This
remedy consists of eighteen Thai medicinal plants. It has long been used in folk medicine to treat fever, measles, chickenpox and skin infection, but there has been no scientific report on antimicrobial activities of this remedy.
Objective: To investigate antimicrobial activities of Kheaw-Hom remedy extracts and its plant ingredients.
Material and Method: Kheaw-Hom remedy and each of its plant ingredients were extracted by maceration in 95% ethanol and decoction in water to obtain ethanolic extract and aqueous extract, respectively. All extracts were tested for antimicrobial activities by microtiter plate-based assay to determine the minimum inhibitory concentration (MIC) and the minimum microbicidal concentration (MMC) values against Staphylococcus aureus (ATCC 25923), methicillin-resistant Staphylococcus aureus (DMST 20651), Staphylococcus epidermidis (ATCC 12228) and Candida albicans (ATCC 90028).
Results: The ethanolic extract of Kheaw-Hom remedy showed antimicrobial activities against Staphylococcus aureus, methicillinresistant Staphylococcus aureus and Staphylococcus epidermidis with MIC values of 0.625, 0.625 and 1.25 mg/ml, respectively and MMC values of 1.25, 0.625 and 2.5 mg/ml, respectively. Among all the ethanolic extracts of its plant ingredients, that of Mammea siamensis showed the highest activity with MIC values of 0.005, 0.005 and 0.039 mg/ml and MMC values of 0.005, 0.005 and 0.039 mg/ml, respectively. The weak activity against bacteria was found in the aqueous extract of some plant ingredients. The ethanolic and aqueous extracts of Kheaw-Hom remedy and the aqueous extract of its plant ingredients had no activity against C. albicans but the ethanolic extract of Sophora exigua showed the highest activities against Candida albicans with MIC values of 0.625 mg/ml and MMC values of 0.625 mg/ml.
Conclusion: The ethanolic extracts of Kheaw-Hom remedy had antimicrobial activity against S. aureus, methicillin-resistant S. aureus and S. epidermidis that are causes of skin infection from chickenpox. These results support the use of Kheaw-Hom remedy for skin infection treatment in chickenpox.

Keywords: Antimicrobial activity, Chickenpox, Kheaw-Hom remedy, Skin infection