Metabolic phenotype analysis of Trichophyton rubrum after laser irradiation.

BACKGROUND: Biological phenotypes are important characteristics of microorganisms, and often reflect their genotype and genotype changes. Traditionally, Trichophyton rubrum (T. rubrum) phenotypes were detected using carbon source assimilation tests, during which the types of tested substances are limited. In addition, the operation is complicated, and only one substance can be tested at once. To observe the changes of the metabolic phenotype of T. rubrum after laser irradiation, a high-throughput phenotype microarray system was used to analyze the metabolism of different carbon, nitrogen, phosphorus and sulfur source substrates in a Biolog metabolic phenotyping system. RESULTS: The strain of T. rubrum used in this study can effectively utilize 33 carbon, 20 nitrogen, 16 phosphorus, and 13 sulfur source substrates prior to laser irradiation. After laser irradiation, the strain was able to utilize 10 carbon, 12 nitrogen, 12 phosphorus, and 8 sulfur source substrates. The degree of utilization was significantly decreased compared with the control. Both groups efficiently utilized saccharides and organic acids as carbon sources as well as some amino acids as nitrogen sources for growth. The number of substrates utilized by T. rubrum after laser irradiation were significantly reduced, especially carbon substrates. Some substrates utilization degree in the laser treated group was higher than control, such as D-glucosamine, L-glutamine, D-2-Phospho-Glyceric Acid, D-glucosamine-6-phosphate, and D-methionine. CONCLUSION: Laser irradiation of T. rubrum may lead to changes in the metabolic substrate and metabolic pathway, thus weakening the activity of the strain.

Growth inhibition of Trichophyton rubrum by laser irradiation: exploring further experimental aspects in an in vitro evaluation study.

BACKGROUND: According to the results of the clinical trials, laser therapy is effective for the treatment of onychomycosis, but the in vitro findings are inconsistent among studies. This study aimed to explore the experimental conditions of laser for the inhibition of Trichophyton rubrum growth in vitro. A 1064-nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser was used to irradiate colonies using a small (6-mm diameter) or large (13-mm diameter) area, and using 300, 408, or 600 J/cm2. The surface temperature of the colony was measured after irradiation and every 2 min. The growth area was calculated until the 7th or 10th day of incubation daily. RESULTS: For the small area group, at 300 J/cm2, the immediate surface temperature was 25.2 ± 0.2°C, but without effect on growth (P = 0.516). At 408 J/cm2, the immediate surface temperature was 32.0 ± 0.4°C; growth was inhibited for 7 days (P < 0.001). At 600 J/cm2, the immediate surface temperature was 38.1 ± 0.4°C; the growth was completely stopped for at least 10 days (P < 0.001). For the large area group, the temperature patterns were similar to those of the small area group, but the highest temperature was lower than in the small area groups, and no growth inhibition effect was observed (all P > 0.05). CONCLUSIONS: When the irradiation area is small, a 1064-nm Nd:YAG laser at 408 or 600 J/cm2 can be effective in suppressing T. rubrum growth in vitro.

Clinical retrospective analysis of long-pulsed 1064-nm Nd:YAG laser in the treatment of onychomycosis and its effect on the ultrastructure of fungus pathogen.

The objective of this study was to analyze retrospectively the clinical efficacy and fungal clearance of long-pulsed 1064-nm Nd:YAG laser for treating onychomycosis and explore the inhibitory effects of laser on the fungus pathogen-induced onychomycosis in vitro. We performed a systematic retrospective analysis of clinical patients (162 effected nails) of onychomycosis treatment applying laser with or without topical ketoconazole ointment and followed up 3 months after treatment. Trichophyton rubrum- and Trichophyton mentagrophytes-induced onychomycosis was irradiated with laser superimposed for different cumulative energy, respectively; then, the areas of fungus colonies and growth curve in different days were showed, and changes in ultrastructures were observed under SEM and TEM. The clinical effective rate and fungal clearance rate in the combined group were higher than those in the laser group; however, there was no significant difference between the two groups. In vitro, the areas of T. rubrum colonies were significantly reduced at days 1, 3, and 5 after irradiation with cumulative laser energy ≥ 6400 J/cm2. When irradiated with cumulative laser energy ≥ 25600 J/cm2, significant difference in the areas of T. mentagrophytes colonies was found at day 5. And ultrastructure of the two strains before and after laser irradiation was damaged at different degrees. This study confirmed that long-pulsed 1064-nm Nd:YAG laser is effective for treating onychomycosis, and the laser irradiation can inhibit the colony growth of T. rubrum and T. mentagrophytes and change their cellular ultrastructures. The mechanism of laser treatment of onychomycosis may be related to direct damage of fungus pathogen.

Determining the optimal parameters of 420-nm intense pulsed light on Trichophyton rubrum growth in vitro.

The effect of and the optimal parameters for intense pulsed light (IPL) with a 420-nm filter on an isolate of the fungus Trichophyton rubrum (T. rubrum) were examined in vitro. Colonies of T. rubrum were irradiated by using 420-nm IPL with various pulse numbers and energies. Colony areas were photographed and compared with those of untreated colonies to assess growth inhibition. Statistically significant inhibition of T. rubrum growth was detected in colonies treated with 12 pulses of greater than or equal to 12 J/cm2. The optimal parameters of 420-nm IPL were 12 pulses of 12 J/cm2. However, more in vitro and in vivo studies are necessary to investigate and explore this mechanism to determine whether IPL would have a potential use in the treatment of fungal infections of the skin.

Photochemical inhibition of Trichophyton rubrum by different compoundings of curcumin.

Recently, we had shown that conidia-derived growth of many dermatophytes can be inhibited by curcumin plus exposure to visible light. This method of photo inactivation should be developed further aiming for an option to stop mycelial growth in superficial tinea. Wells of microtitre plates were inoculated with either mycelial or conidial elements collected from 5 strains of Trichophyton rubrum. Then either micellar curcumin or curcumin dissolved with DMSO was added and after 20 min the wells were filled up with Sabouraud broth. Thereafter the assays were irradiated once with visible light (wave length 420 nm, 20 J/cm2 ) and fungal growth was monitored photometrically. Identical effects were measured with conidia and mycelial elements of all 5 T. rubrum strains. Curcumin dissolved with DMSO plus irradiation had a marked dose-dependent inhibitory effect on fungal growth that was almost complete with 5.0 mg/L (P < .01) over a period of 9 days. In contrast, the same procedure with micellar curcumin had no inhibitory effect on growth obtained from conidia or mycelial elements. Mycelial elements of T. rubrum and its conidia are equally sensitive to photochemical inactivation with curcumin and the galenic compounding of curcumin is essential to achieve this photochemical effect.

Clinical laser treatment of toenail onychomycoses.

Onychomycoses are fungal infections of the fingernails or toenails having a prevalence of 3% among adults and accounts for 50% of nail infections. It is caused by dermatophytes, non-dermatophyte filamentous fungi, and yeasts. Compressions and microtraumas significantly contribute to onychomycosis. Laser and photodynamic therapies are being proposed to treat onychomycosis. Laser light (1064 nm) was used to treat onychomycosis in 156 affected toenails. Patients were clinically followed up for 9 months after treatment. Microbiological detection of fungal presence in lesions was accomplished. A total of 116 samples allowed the isolation of at least a fungus. Most of nails were affected in more than two thirds surface (some of them in the full surface). In 85% of cases, after 18 months of the onset of treatment, culture turned negative. After 3 months months, only five patients were completely symptom-free with negative culture. In 25 patients, only after 6 months, the absence of symptoms was achieved and the cultures negativized; in 29 patients, 9 months were required. No noticeable adverse effects were reported. This study reinforces previous works suggesting the applicability of laser therapies to treat toenail onychomycosis.

Singlet oxygen luminescence kinetics under PDI relevant conditions of pathogenic dermatophytes and molds.

A treatment of onychomycosis using the photodynamic effect would be a favorable alternative to currently used antimycotic drugs. This study should be considered as a first step towards development and control of an efficient photodynamic inactivation of onychomycosis causative pathogens. Here, we evaluate the usage of time-resolved 2D singlet oxygen luminescence detection in combination with 2D fluorescence scanning as a tool to understand the behavior of the photosensitizer when applied to fungi on Petri dishes. To investigate the interaction of photosensitizer with fungi in various concentrations and in different stages of live, a photodynamic inactivation was avoided by keeping the samples in darkness. Scans of singlet oxygen luminescence and photosensitizer fluorescence were performed over a period of 24days. Two different photosensitizer, a cationic porphyrin and cationic corrole and two fungi strains, the dermatophyte Trichophyton rubrum and the mold Scopulariopsis brevicaulis, were investigated in this study. The two-dimensional correlation of photosensitizer fluorescence and singlet oxygen luminescence revealed differences in the diffusion of both photosensitizer. Even though the singlet oxygen luminescence was quenched with increasing growth of fungi, it was found that the kinetics of singlet oxygen luminescence could be detected on Petri dishes for both photosensitizers and both fungi strains for up to seven days.

[Effect of intense pulsed light on Trichophyton rubrum growth in vitro].

OBJECTIVE: To investigate the inhibitory effect of 420 nm intense pulsed light on Trichophyton rubrum growth in vitro and explore the mechanism. METHODS: The fungal conidia were divided into treatment group with intense pulse light irradiation and control group without irradiation. The surface areas of the fungal colonies were photographed before irradiation and on the 2nd and 3rd days after irradiation to observe the changes in fungal growth. The viability of the fungus in suspension was detected at 6 h after irradiation using MTT assay. The intracellular reactive oxygen species (ROS) level in the fungus was determined using DCFH-DA fluorescent probe, and the MDA content was detected using TBA method. RESULTS: Intense pulse light (420 nm) irradiation caused obvious injuries in Trichophyton rubrum with the optimal effective light dose of 12 J/cm2 in 12 pulses. At 6 h after the irradiation, the fungus in suspension showed a 30% reduction of viability (P<0.05), and the fungal colonies showed obvious growth arrest without further expansion. Compared to the control group, the irradiated fungus showed significant increases in ROS level and MDA content (P<0.05). CONCLUSION: Intense pulse light (420 nm) irradiation can induce oxidative stress in Trichophyton rubrum to lead to fungal injuries and death.

In vitro fungicidal effects of methylene blue at 625-nm.

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/cm2 . Colony counts were performed and compared to untreated controls. Doses of 24, 40 and 60 J/cm2 all produced kill rates of over 94%. A lower rate of delivery (7.80 mW/cm2 ) was shown to be a greater inhibitor of T. rubrum than a higher rate of delivery (120 mW/cm2 ). Photodynamic therapy with methylene blue (MB) at 625 nm using a low rate of delivery at doses of 24, 40 and 60 J/cm2 is an effective inhibitor of T. rubrum. A rate of delivery of 7.80 mW/cm2 is a significantly greater inhibitor of T. rubrum than a rate of 120 mW/cm2 when applying 625-nm light in PDT using MB.

Comparison of photoinactivation of T. rubrum by new methylene blue (NMB) and indocyanine green (EmunDo®).

BACKGROUND: Superficial mycotic skin infections which are predominantly caused by Trichophyton rubrum, poorly responsd to conventional therapies. A great amount of attention has focused on finding more effective treatments. The current work is aimed to compare the effectiveness of phoinactivation of Trichophyton rubrum by two relatively new photosensitizers: a phenothiazinium dye(New methylene blue) and Indocyanine green (EmunDo®). MATERIALS AND METHODS: A Final inoculum of T. rubrum which corresponded to 106 colony forming unit per milliliter (CFUml-1) was prepared. Antimicrobial Photodynamic treatment (aPDT) of T. rubrum was carried out by either EmunDo® (1mg/ml, Infra-red laser (IRL, λ=810nm, Energy Density 55J/cm2)) or NMB (10µM, Red laser (RL), λ=630nm, Energy Density of 5J/cm2). The suspensions thereafter were subcultured on Sabouraud dextrose agar (SDA) and were counted on due time. based on colony-forming unit per milliliter (CFU/ml). RESULTS: aPDT with either EmunDo® (E) or NMB (N) considerably diminished the viability of inoculated T. rubrum with respective reduction of 0.64 log and 0.4 log compared to the control group (P<0.001). No significant difference was found between two laser only groups (P=0.79) and two aPDT groups (P=0.73), however significant reduction of T. rubrum in red laser only group (P=0.04) and EmunDo® only group (P=0.04) was found as compared to the control group (P<0.05). CONCLUSION: The study provides evidence regarding satisfactory photodynamic inactivation of T. rubrum with EmunDo® or NMB as photosensitizers. Irradiation by only red laser source was found superior to only infra-red laser source. Dark toxicity of EmunDo® was more successful than new methylene blue dye.

In Vitro Antimicrobial Photodynamic Therapy Against Trichophyton mentagrophytes Using New Methylene Blue as the Photosensitizer. / Terapia fotodinámica antimicrobiana in vitro aplicada sobre Trichophyton mentagrophytes con nuevo azul de metileno como fotosensibilizador.

INTRODUCTION AND OBJECTIVES: Antimicrobial photodynamic therapy combines the use of a photosensitizing drug with light and oxygen to eradicate pathogens. Trichophyton mentagrophytes is a dermatophytic fungus able to invade the skin and keratinized tissues. We have investigated the use of new methylene blue as the photosensitizing agent for antimicrobial photodynamic therapy to produce the in vitro inactivation of T mentagrophytes. MATERIAL AND METHODS: A full factorial design was employed to optimize the parameters for photoinactivation of the dermatophyte. The parameters studied were new methylene blue concentration, contact time between the photosensitizing agent and the fungus prior to light treatment, and the fluence of red light (wavelength, 620-645nm) applied. RESULTS: The minimum concentration of new methylene blue necessary to induce the death of all T. mentagrophytes cells in the initial suspension (approximate concentration, 106 colony forming units per milliliter) was 50µM for a fluence of 81J/cm2 after a contact time of 10minutes with the photosensitizing-agent. Increasing the concentration to 100µM allowed the fluence to be decreased to 9J/cm2. CONCLUSIONS: Comparison of our data with other published data shows that the susceptibility of T. mentagrophytes to antimicrobial photodynamic therapy with new methylene blue is strain-dependent. New methylene blue is a photosensitizing agent that should be considered for the treatment of fungal skin infections caused by this dermatophyte.

Comparative Sensitivity of Trichophyton and Aspergillus Conidia to Inactivation by Violet-Blue Light Exposure.

OBJECTIVE: To investigate the use of 405 nm light for inhibiting the growth of selected species of dermatophytic and saprophytic fungi. BACKGROUND DATA: The increasing incidence and resilience of dermatophytic fungal infections is a major issue, and alternative treatment methods are being sought. METHODS: The sensitivity of the dermatophytic fungi Trichophyton rubrum and Trichophyton mentagrophytes to 405 nm violet-blue light exposure was investigated, and the results compared with those obtained with the saprophytic fungus Aspergillus niger. Microconidia of T. rubrum and T. mentagrophytes and conidia of A. niger were seeded onto Sabauroud dextrose agar plates and irradiated with 405 nm light from an indium-gallium-nitride 99-DIE light-emitting diode (LED) array and the extent of inhibition was measured. RESULTS: Germination of the microconidia of the Trichophyton species was completely inhibited using an irradiance of 35 mW/cm(2) for 4 h (dose of 504 J/cm(2)). A. niger conidia showed greater resistance, and colonial growth developed after light exposure. In liquid suspension tests, 405 nm light dose levels of 360, 720, and 1440 J/cm(2) resulted in complete inactivation of T. rubrum microconidia, whereas A. niger showed greater resistance, and at the highest dose level applied (1440 J/cm(2)) although A niger hyphae were completely inactivated, only a 3-log10 reduction of a 5-log10 conidial suspension was achieved. CONCLUSIONS: The study results demonstrate the relatively high sensitivity of Trichophyton microconidia to 405 nm violet-blue light, and this is may be of potential interest regarding the control and treatment of dermatophyte infections.

Trichophyton rubrum is inhibited by free and nanoparticle encapsulated curcumin by induction of nitrosative stress after photodynamic activation.

Antimicrobial photodynamic inhibition (aPI) utilizes radical stress generated from the excitation of a photosensitizer (PS) with light to destroy pathogens. Its use against Trichophyton rubrum, a dermatophytic fungus with increasing incidence and resistance, has not been well characterized. Our aim was to evaluate the mechanism of action of aPI against T. rubrum using curcumin as the PS in both free and nanoparticle (curc-np) form. Nanocarriers stabilize curcumin and allow for enhanced solubility and PS delivery. Curcumin aPI, at optimal conditions of 10 µg/mL of PS with 10 J/cm² of blue light (417 ± 5 nm), completely inhibited fungal growth (p<0.0001) via induction of reactive oxygen (ROS) and nitrogen species (RNS), which was associated with fungal death by apoptosis. Interestingly, only scavengers of RNS impeded aPI efficacy, suggesting that curcumin acts potently via a nitrosative pathway. The curc-np induced greater NO˙ expression and enhanced apoptosis of fungal cells, highlighting curc-np aPI as a potential treatment for T. rubrum skin infections.

In vitro combination therapy using low dose clotrimazole and photodynamic therapy leads to enhanced killing of the dermatophyte Trichophyton rubrum.

BACKGROUND: Superficial infections of the skin and mucous membranes caused by dermatophyte fungi are amongst the most common and challenging infections to treat. Previously we demonstrated the phototoxic effects of photodynamic therapy (PDT) towards Trichophyton rubrum, using a green laser to photoactivate Rose Bengal (RB). The aim of this study was to evaluate whether we could; (1) achieve a similar effect using an inexpensive light-emitting diode (LED) to photoactivate RB and (2) to evaluate whether our PDT regime could be combined with standard antifungal drug therapy and increase its effectiveness. METHODS: We designed and built our own inexpensive green (530 nm) LED source and tested its efficacy as part our RB-PDT regime in vitro against T. rubrum. We also examined the potential benefits of incorporating PDT as part of combination therapy and whether the order in which this was done had an impact. First we subjected spore suspensions to sub-inhibitory concentrations of a number of antifungal agents (CLT, MCZ and TRB) for 72 hours followed by RB-PDT. Secondly we subjected spore suspensions to sub-inhibitory PDT followed by drug treatment and evaluated if there were any changes to the minimum inhibitory concentrations (MICs) of the drugs tested. RESULTS: The optimal conditions for photoinactivation of T. rubrum using RB-PDT alone were 140 µM of RB and 24 J/cm2 of LED (equating to a 30-minute exposure). These parameters also caused a 100% reduction in the viability of the pathogenic yeast Candida albicans and the model fungus Saccharomyces cerevisiae. By combining our RB-PDT regime as an adjunct to antifungal drugs we were able to dramatically reduce the exposure times. Treatment of spore suspensions using a sub-inhibitory dose of clotrimazole (CLT) followed by RB-PDT, this order was critical, significantly reduced the exposure times required to achieve 100% inhibition of T. rubrum to 15 minutes as compared to RB-PDT alone. CONCLUSIONS: The combination of antifungal drug and RB-PDT represents an attractive alternative to the current antifungal therapies used to treat superficial fungal diseases. Our approach has the potential to reduce treatment times and drug dosages which can also reduce drug toxicity and improve patient compliance.

In vitro fungicidal photodynamic effect of hypericin on Trichophyton spp.

Hypericin is a natural photosensitizer used in photodynamic therapy (PDT), which has shown in vitro antifungal effect against Candida spp. The aim of this study was to evaluate the in vitro fungicidal effect of hypericin-PDT on dermatophytes. Trichophyton rubrum and Trichophyton mentagrophytes strains were incubated with different concentrations of hypericin for different times and exposed to light-emitting diode lamp (602 ± 10 nm, 10.3 mW cm(-2), and fluence 37 J cm(-2)). Using the optimal incubation time, 60 min, a 3-log fungicidal effect was achieved with hypericin concentration ranges of 10-20 µM for T. rubrum and 20-50 µM for T. mentagrophytes (p = 0.95). Confocal fluorescence microscopy showed the localization of hypericin inside the dermatophytes diffusely distributed in the cytoplasm of conidia and hyphae and outside the nucleus. In conclusion, hypericin-PDT has a fungicidal effect in vitro on dermatophytes. Hypericin seems to be a promising photosensitizer to treat localized dermatophytic infections such as tinea pedis and onychomycosis.

Silicon phthalocyanine 4 phototoxicity in Trichophyton rubrum.

Trichophyton rubrum is the leading pathogen that causes long-lasting skin and nail dermatophyte infections. Currently, topical treatment consists of terbinafine for the skin and ciclopirox for the nails, whereas systemic agents, such as oral terbinafine and itraconazole, are also prescribed. These systemic drugs have severe side effects, including liver toxicity. Topical therapies, however, are sometimes ineffective. This led us to investigate alternative treatment options, such as photodynamic therapy (PDT). Although PDT is traditionally recognized as a therapeutic option for treating a wide range of medical conditions, including age-related macular degeneration and malignant cancers, its antimicrobial properties have also received considerable attention. However, the mechanism(s) underlying the susceptibility of dermatophytic fungi to PDT is relatively unknown. As a noninvasive treatment, PDT uses a photosensitizing drug and light, which, in the presence of oxygen, results in cellular destruction. In this study, we investigated the mechanism of cytotoxicity of PDT in vitro using the silicon phthalocyanine (Pc) 4 [SiPc(OSi(CH3)2(CH2)3N(CH3)2)(OH)] in T. rubrum. Confocal microscopy revealed that Pc 4 binds to cytoplasmic organelles, and upon irradiation, reactive oxygen species (ROS) are generated. The impairment of fungal metabolic activities as measured by an XTT (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxyanilide inner salt) assay indicated that 1.0 µM Pc 4 followed by 670 to 675 nm light at 2.0 J/cm(2) reduced the overall cell survival rate, which was substantiated by a dry weight assay. In addition, we found that this therapeutic approach is effective against terbinafine-sensitive (24602) and terbinafine-resistant (MRL666) strains. These data suggest that Pc 4-PDT may have utility as a treatment for dermatophytosis.

An in vitro study of the photodynamic effect of rose bengal on Trichophyton rubrum.

Onychomycosis, a fungal infection of the finger or toenails, is predominantly caused by Trichophyton rubrum. Treatment is difficult due to high recurrence rates and problems with treatment compliance. For these reasons, alternative therapies are needed. Here we describe the photoactivation of Rose Bengal (RB) using a green laser (λ = 532 nm) at fluences of 68, 133 and 228 J/cm(2) , and assess its fungicidal activity on T. rubrum spore suspensions. A 140 µM RB solution was able to induce a fungicidal effect on T. rubrum when photosensitized with the fluence of 228 J/cm(2) . RB photosensitization using a green laser provides a potential novel treatment for T. rubrum infections.

An investigation into the inhibitory effect of ultraviolet radiation on Trichophyton rubrum.

Fungal infection of nails, onychomycosis, is predominantly caused by Trichophyton rubrum. This infection is an important public health concern due to its persistent nature and high recurrence rates. Alternative treatments are urgently required. One such alternative is phototherapy involving the action of photothermal or photochemical processes. The aim of this novel study was to assess which wavelengths within the ultraviolet (UV) spectrum were inhibitory and equally important nail transmissible. Initial irradiations of T. rubrum spore suspensions were carried out using a tunable wavelength lamp system (fluence ≤3.1 J/cm(2)) at wavelengths between 280 and 400 nm (UVC to UVA) to evaluate which wavelengths prevented fungal growth. Light-emitting diodes (LEDs) of defined wavelengths were subsequently chosen with a view to evaluate and potentially implement this technology as a low-cost "in-home" treatment. Our experiments demonstrated that exposure at 280 nm using an LED with a fluence as low as 0.5 J/cm(2) was inhibitory, i.e., no growth following a 2-week incubation (p < 0.05; one-way ANOVA), while exposure to longer wavelengths was not. A key requirement for the use of phototherapy in the treatment of onychomycosis is that it must be nail transmissible. Our results indicate that the treatment with UVC is not feasible given that there is no overlap between the antifungal activity observed at 280 nm and transmission through the nail plate. However, a potential indirect application of this technology could be the decontamination of reservoirs of infection such as the shoes of infected individuals, thus preventing reinfection.

Inactivation of pathogenic dermatophytes by ultraviolet irradiation in swimming pool thermal water.

The effect of ultraviolet (UV) radiation from low-pressure mercury lamp against some pathogenic dermatophytes species such as Epidermophyton floccosum, Trichophyton mentagrophytes, Trichophyton rubrum, Trichophyton schoenleinii, Trichophyton tonsurans and Trichophyton violaceum suspended in thermal water was evaluated in laboratory-scale condition at various times. The main results showed that within 120 s of exposure, all species of dermatophytes are completely inactivated, which was evidenced by the absence of fungal regrowth, while after 60 s only T. tonsurans was recovered, with a reduction of 3.28 log. Shorter exposure times were not enough to completely inactivate all dermatophytes species. The samples treated with UV radiation for 120 s did not give evidence of fungal regrowth indicating that this disinfectant action is persistent over time. In conclusion, UV radiation can be proposed to reduce the risk of infection by dermatophytes eventually present in swimming pools that use thermal water.

Antifungal efficacy of lasers against dermatophytes and yeasts in vitro.

PURPOSE: Approximately 2-13% of the world population suffers from onychomycosis. Recently, lasers have been introduced for treatment. However, no effect was found with in vitro laser irradiation of pathogens on agar plates. This study aimed to investigate the efficacy of laser irradiation against fungi using an alternative in vitro approach. MATERIALS AND METHODS: Lasers of 808, 980 and 1064 nm were used to heat cell culture media and a nail clipping. Trichophyton rubrum. T. interdigitale. Microsporum gypseum. Candida albicans. C. parapsilosis, and C. guilliermondii species were subcultured and subjected to laser treatments (808/980 nm: 9-27 J/cm(2), 6 ms, 12 × 12 or 12 × 50 mm and 1064 nm: 50-240 J/cm(2), 90 ms, 5-10 mm). After irradiation, the fungal elements were transferred onto agar plates using conventional and Drigalski spatulas and were incubated for 6 days. RESULTS: The highest increase in temperature was found using a 980-nm laser with a pulse duration of 6 ms and a fluence of 27 J/cm(2). The histology work-up revealed a dissection of the nail plate from the nail bed tissue after laser irradiation. Growth inhibition was only found for C. guilliermondii and T. interdigitale. All other pathogens presented only reduced growth, and C. albicans growth was unaffected. CONCLUSIONS: This study demonstrates a clear thermal effect for linear scanning 980-nm and long-pulsed 1064-nm laser systems on either nail clippings or cell culture media. Complete pathogen growth impairment was achieved if temperatures were measured above 50 °C. The results for the 1064-nm system were almost comparable to 980 nm results.