Anti-infective effects of traditional household remedies described in the national list of essential medicines, Thailand, on important human pathogens

Abstract Three polyherbal household formulations, namely Kheaw-Hom (KH), Learng-Pid-Sa-Mud (LP), and Ummaluk-kawatee (UM), in the National List of Essential Medicines have been claimed to be effective for the treatment of fever, diarrhea, and cough. Therefore, this study aimed to scientifically evaluate the anti-infective properties of these formulations. The antibacterial and anti-biofilm formation activities of KH, LP, and UM ethanol extracts against Pseudomonas aeruginosa, Acinetobacter baumannii, Staphylococcus aureus, and Staphylococcus epidermidis were determined by a broth microdilution method and a crystal violet assay, whereas their synergistic effects with certain antibiotics were tested by a diffusion method. The lowest concentration of the extract that inhibited ≥90 % of bacterial growth (IC90) of both methicillin resistant S. aureus and biofilm‐forming S. epidermidis was 31.3−125 μg/mL. These extracts significantly inhibited the biofilm formation activities of Gram-positive pathogens and exhibited notable synergistic effects with certain antibiotics against these pathogens. Therefore, it can be proposed that the antibacterial and anti-biofilm formation properties of KH, LP, and UM against Gram-positive pathogens may be involved in their traditional applications. Moreover, these formulations exhibited synergistic interactions with certain antibiotics against these pathogens, and this must be highlighted in further studies on their detailed mechanisms of action.