In vitro fungicidal effects of methylene blue at 625‐nm

Abstract

The aim of the study is to confirm the effectiveness of photodynamic therapy (PDT) as a significant inhibitor of Trichophyton rubrum (T. rubrum) and to determine the most appropriate dose and rate of delivery. Trichophyton rubrum is the most common dermatophyte worldwide, responsible for the majority of superficial fungal infections. The traditional treatment of T. rubrum has known adverse effects. An alternative treatment is warranted. Photosensitised T. rubrum specimens were treated with 625-nm light at doses of 3, 12, 24, 40 and 60 J/cm . Colony counts were performed and compared to untreated controls. Doses of 24, 40 and 60 J/cm all produced kill rates of over 94%. A lower rate of delivery (7.80 mW/cm ) was shown to be a greater inhibitor of T. rubrum than a higher rate of delivery (120 mW/cm ). Photodynamic therapy with methylene blue (MB) at 625 nm using a low rate of delivery at doses of 24, 40 and 60 J/cm is an effective inhibitor of T. rubrum. A rate of delivery of 7.80 mW/cm is a significantly greater inhibitor of T. rubrum than a rate of 120 mW/cm when applying 625-nm light in PDT using MB.

Different susceptibility of spores and hyphae of Trichophyton rubrum to methylene blue mediated photodynamic treatment in vitro

“…The inhibition rate increased with concentration and light dose with 1.25 μg/mL MB, red light at the dose of over 40 J/cm 2 completely killed all the spores. Guffey et.al 19 found that at MB 2 μmmol/L (about 0.64 μg/mL), the spores of T rubrum were completely killed by 625 nm red light at the dose of 60 J/cm 2 , which is approximately consistent with our results.…”

“…The present study confirms that MB-PDT has a definite inhibitory effect on T rubrum, which is consistent with previous studies. 19 This study also evaluated the susceptibility of the microspores and hyphae of T rubrum to MB-PDT, respectively. Our results revealed that both spores and hyphae could be successfully inhibited by MB-PDT.…”

“…Several studies have demonstrated MB mediated PDT (MB‐PDT) has the definite inhibitory effect on fungi, but MB alone did not have significant antifungal activity 17,18 . The antifungal effect of MB‐PDT on T rubrum has been reported in several papers; however, the exact intervention parameters for maximum efficacy remain to be elucidated 19 . Furthermore, previous studies mainly focused on the spore form of T rubrum , but rarely on its hyphal form even though the latter is its main pathogenic form in vivo.…”

In vitro evaluation of photodynamic activity of methylene blue against Trichophyton verrucosum azole‐susceptible and ‐resistant strains

“…Currently, photodynamic therapy has been revealed to be an efficient therapeutic solution against a variety of fungi, including antropophilic, that is, Trichophyton rubrum, and zoophilic, that is, Trichophyton mentagrophytes dermatophytes [30,31]. Several studies have also demonstrated that methylene blue mediated photodynamic therapy has the definite better inhibitory effect on fungi, which solution was tested in detail against T. rubrum [32,33]. Methylene blue is a photosensitiser that has a strong absorption band in the red light wavelength range, presents low toxicity toward human and animal cells, and is relatively inexpensive [34].…”

Evaluation of the photodynamic efficacy and effects of haematoporphyrin monomethyl ether on Trichophyton rubrum microconidia in vitro

“…PS plays a key role among the three elementary components in aPDT. Previous in vitro studies demonstrated that T rubrum could be effectively killed by a wide variety of PSs including rose bengal (RB), 11 5‐aminolevulinic acid (5‐ALA), 12 curcumin, 13 indocyanine green (ICG), 14 methylene blue (MB), 15 toluidine blue (TBO), 16 hypericin 17 and phthalocyanine 4 (Pc 4) 18 . Several clinical case reports also revealed that 5‐ALA–mediated aPDT could completely cure the onychomycosis and tinea cruris in patients caused by T rubrum 19‐21 …”