Skin mycoses are caused mainly by dermatophytes, which are fungal species that primarily infect areas rich in keratin such as hair, nails and skin. Significantly, there are increasing rates of antimicrobial resistance among dermatophytes, especially for Trichophyton rubrum, the most frequent etiologic agent worldwide. Hence, investigators have been developing new therapeutic approaches, including photodynamic treatment. Photodynamic therapy utilizes a photosensitive substance activated by a light source of a specific wavelength. The photoactivation induces cascades of photochemicals and photobiological events that cause irreversible changes in the exposed cells. Although photodynamic approaches are well established experimentally for the treatment of certain cutaneous infections, there is limited information about its mechanism of action for specific pathogens as well as the risks to healthy tissues. In this work, we have conducted a comprehensive review of the current knowledge of photodynamic therapy as it specifically applies to fungal diseases. The data to date suggests that photodynamic treatment approaches hold great promise for combating certain fungal pathogens, particularly dermatophytes.

Fungal infections are underestimated threats that affect over 1 billion people, andCandidaspp.,Cryptococcusspp., andAspergillusspp. are the 3 most fatal fungi. The treatment of these infections is performed with a limited arsenal of antifungal drugs, and the class of the azoles is the most used. Although these drugs present low toxicity for the host, there is an emergence of therapeutic failure due to azole resistance. Drug resistance normally develops in patients undergoing azole long-term therapy, when the fungus in contact with the drug can adapt and survive. Conversely, several reports have been showing that resistant isolates are also recovered from patients with no prior history of azole therapy, suggesting that other routes might be driving antifungal resistance. Intriguingly, antifungal resistance also happens in the environment since resistant strains have been isolated from plant materials, soil, decomposing matter, and compost, where important human fungal pathogens live. As the resistant fungi can be isolated from the environment, in places where agrochemicals are extensively used in agriculture and wood industry, the hypothesis that fungicides could be driving and selecting resistance mechanism in nature, before the contact of the fungus with the host, has gained more attention. The effects of fungicide exposure on fungal resistance have been extensively studied inAspergillus fumigatusand less investigated in other human fungal pathogens. Here, we discuss not only classic and recent studies showing that environmental azole exposure selects cross-resistance to medical azoles inA.fumigatus, but also how this phenomenon affectsCandidaandCryptococcus, other 2 important human fungal pathogens found in the environment. We also examine data showing that fungicide exposure can select relevant changes in the morphophysiology and virulence of those pathogens, suggesting that its effect goes beyond the cross-resistance.

Although the most accepted mechanisms of action of amphotericin B and azoles are related to ergosterol, it is possible that these drugs have other effects on the fungal cell. In the present study, the role of endogenous reactive oxygen species (ROS) and peroxynitrite produced by azoles and amphotericin B in the fungus Cryptococcus gattii were examined. We studied distinct parameters to evaluate the effect of oxidative and nitrosative stresses induced by these drugs in C. gattii cells: lipid peroxidation, ergosterol content, ROS and peroxynitrite production, enzymatic activity of the antioxidant system and the in vitro interaction of antifungal drugs with a peroxidase inhibitor, a superoxide dismutase inhibitor and a peroxynitrite scavenger. The data demonstrated that itraconazole led to ROS formation and lipid peroxidation in C. gattii cells in the early stages of the treatment; this did not occur with fluconazole. This phenomenon strongly increased the activities of enzymes of the antioxidant system. These results were confirmed by synergism observed between the catalase inhibitor and itraconazole. Amphotericin B caused lipid peroxidation in C. gattii cells through a greatly enhanced production of oxidative and nitrosative radicals with increased peroxidase activity. These data were confirmed by the synergism between the catalase/superoxide dismutase inhibitors and amphotericin B. In addition, the effect of this antifungal was antagonized by the peroxynitrite scavenger. Oxidative and nitrosative bursts play an important role in the antifungal activity of itraconazole and amphotericin B against C. gattii.

Extracellular vesicles (EVs) has been considered an alternative process for intercellular communication. EVs release by filamentous fungi and the role of vesicular secretion during fungus-host cells interaction remain unknown. Here, we identified the secretion of EVs from the pathogenic filamentous fungus, Aspergillus fumigatus. Analysis of the structure of EVs demonstrated that A. fumigatus produces round shaped bilayer structures ranging from 100 to 200 nm size, containing ergosterol and a myriad of proteins involved in REDOX, cell wall remodeling and metabolic functions of the fungus. We demonstrated that macrophages can phagocytose A. fumigatus EVs. Phagocytic cells, stimulated with EVs, increased fungal clearance after A. fumigatus conidia challenge. EVs were also able to induce the production of TNF-α and CCL2 by macrophages and a synergistic effect was observed in the production of these mediators when the cells were challenged with the conidia. In bone marrow-derived neutrophils (BMDN) treated with EVs, there was enhancement of the production of TNF-α and IL-1β in response to conidia. Together, our results demonstrate, for the first time, that A. fumigatus produces EVs containing a diverse set of proteins involved in fungal physiology and virulence. Moreover, EVs are biologically active and stimulate production of inflammatory mediators and fungal clearance.

Fifty clinical isolates of Trichophyton rubrum were selected to test with ketoconazole, fluconazole, itraconazole, griseofulvin, and terbinafine by following the National Committee for Clinical Laboratory Standards susceptibility testing guidelines for filamentous fungi (M38-A). In addition, other susceptibility testing conditions were evaluated: (i) three medium formulations including RPMI 1640 (standard medium), McVeigh & Morton (MVM), and Sabouraud dextrose broth (SDB); (ii) two incubation temperatures (28 and 35°C); and (iii) three incubation periods (4, 7, and 10 days). The strains Candida parapsilosis (ATCC 22019), Candida krusei (ATCC 6258), T. rubrum (ATCC 40051), and Trichophyton mentagrophytes (ATCC 40004) were included as quality controls. All isolates produced clearly detectable growth only after 7 days of incubation. MICs were significantly independent of the incubation temperature (28 or 35°C) ( P < 0.05). Different incubation periods resulted in MICs which were consistently different for each medium when azoles and griseofulvin were tested ( P < 0.05). MICs obtained from different media at the same incubation time for the same isolate were significantly different when azoles and griseofulvin were tested ( P < 0.05). MICs were consistently higher (usually 1 to 2 dilutions) with RPMI than with MVM or SDB ( P < 0.05). When terbinafine was tested, no parameter had any influence on MICs ( P < 0.05). RPMI standard medium appears to be a suitable testing medium for determining the MICs for T. rubrum . MICs obtained at different incubation times need to be correlated with clinical outcome to demonstrate which time has better reliability.