Combined Effect of Heat, Essential Oils and Salt on the Fungicidal Activity against Trichophyton mentagrophytes in Foot Bath

Abstract

This work was originally undertaken to determine the effective conditions of essential oils against Trichophyton mentagrophytes in vitro for the treatment of tinea pedis in a foot bath. Agar blocks implanted with T. mentagrophytes were immersed in 0.1% aqueous agar containing two-fold dilutions of essential oils with or without sodium chloride at 27 C, 37 C and 42 C for 10 and 20 min. The number of surviving mycelia on the agar blocks was determined from the standard curves of the colony diameter and original inocula of the conidia. At the same time, the thermal effect on the cellular morphology was examined using SEM. Most fungal mycelia 99.7% were killed after treatment at 42 C for 20 min without essential oil. The fungicidal activity of essential oils was markedly enhanced by treating at 42 C for 20 min as compared with that at 27 C, showing 1/4 1/32-fold reduction of minimum fungicidal concentration MFC to kill 99.99% . The order of the fungicidal activity of 11 essential oils was oregano, thyme thymol, cinnamon bark lemongrass clove, palmarose, peppermint, lavender geranium Bourbon, tea tree thyme geraniol oils. MFCs were further reduced to 1/2 1/8 by the addition of 10% sodium chloride. The salt effect was explained, at least partly, by an increase in mycelial adsorption of antifungal constituents in the presence of sodium chloride. Considerable hyphal damage was done at 27 C by the essential oils, but no further alteration in morphology of the hyphae treated at 42 C with or without oil was observed by SEM. The inhibitory effect of heat and oils was also observed against mycelia of T. rubrum and conidia of T. mentagrophytes. Thermotherapy combined with essential oils and salt would be promising to treat tinea pedis in a foot bath.

Imidazolium salts with antifungal potential against multidrug-resistant dermatophytes

“…The dried samples were finally coated with osmium in an osmium plasma coater (Nippon laser & Electronics Laboratory, Nagoya City, Japan), and examined using a Carl Zeiss MEV Evo 50 (Inouye et al . ).…”

Antifungal properties of Japanese cedar essential oil from waste wood chips made from used sake barrels

“…Therefore, immersion treatment in EO-USB seems to be as effective as itraconazole treatment. Inouye et al reported that mycelia of T. mentagrophytes were 10-100-fold more sensitive to EOs than conidia (1). Similarly, 100 µg/ml of EO-USB exhibited strong antifungal activity against T. rubrum mycelia with a killing ratio of 98%.…”

“…The antifungal activity of EO-USB against T. rubrum was estimated according to the method described by Inouye et al (1). In brief, the microconidial suspension (10 7 conidia) was spread uniformly on a Petri dish (8 cm in diameter) containing 15 ml of potato dextrose and 3% agar.…”

“…Agar blocks covered with T. rubrum mycelia were immersed in EO-USB solution, and the number of mycelia that survived was determined according to the method described by Inouye et al (1). As shown in Fig.…”

“…is widespread in humans and recurs frequently. Tinea pedis is usually treated by the administration of topical or oral medicines; however, essential oils (EOs) are also effective for treating dermatophytosis (1)(2)(3).…”