Relevant insights into onychomycosis' pathogenesis related to the effectiveness topical treatment

In Vitro and Ex Vivo Biofilm-Forming Ability of Rhinocladiella similis and Trichophyton rubrum Isolated from a Mixed Onychomycosis Case

Infections caused by biofilm-forming agents have important implications for world health. Mixed infections, caused by more than one etiological agent, are also an emerging problem, especially regarding the standardization of effective diagnosis and treatment methods. Cases of mixed onychomycosis (OM) have been reported; however, studies on the microbial interactions between the different fungi in biofilms formed on nails are still scarce. We describe a case of mixed OM caused by the dermatophyte Trichophyton rubrum and the black yeast-like fungus Rhinocladiella similis. Identical growths of both fungi were observed in more than 50 cultures from different nail samples. Additionally, both species were able to form organized single and mixed biofilms, reinforcing the participation of both fungi in the etiology of this OM case. R. similis seemed to grow faster during the process, suggesting that T. rubrum benefits from biofilm development when in combination. Moreover, the biofilm of the Rhinocladiella isolate exhibited exacerbated production of the extracellular matrix, which was not observed with that of a Rhinocladiella reference strain, suggesting that the isolate had natural abilities that were possibly perfected during development in the nail of the patient.

Case of Mixed Infection of Toenail Caused by Candida parapsilosis and Exophiala dermatitidis and In Vitro Effectiveness of Propolis Extract on Mixed Biofilm

Onychomycosis is a chronic fungal nail infection caused by several filamentous and yeast-like fungi, such as the genus Candida spp., of great clinical importance. Black yeasts, such as Exophiala dermatitidis, a closely related Candida spp. species, also act as opportunistic pathogens. Fungi infectious diseases are affected by organisms organized in biofilm in onychomycosis, making treatment even more difficult. This study aimed to evaluate the in vitro susceptibility profile to propolis extract and the ability to form a simple and mixed biofilm of two yeasts isolated from the same onychomycosis infection. The yeasts isolated from a patient with onychomycosis were identified as Candida parapsilosis sensu stricto and Exophiala dermatitidis. Both yeasts were able to form simple and mixed (in combination) biofilms. Notably, C. parapsilosis prevailed when presented in combination. The susceptibility profile of propolis extract showed action against E. dermatitidis and C. parapsilosis in planktonic form, but when the yeasts were in mixed biofilm, we only observed action against E. dermatitidis, until total eradication.

Antifungal and Antibiofilm Activity of Riparin III against Dermatophytes

The ability of dermatophytes to develop biofilms is possibly involved in therapeutic failure because biofilms impair drug effectiveness in the infected tissues. Research to find new drugs with antibiofilm activity against dermatophytes is crucial. In this way, riparins, a class of alkaloids that contain an amide group, are promising antifungal compounds. In this study, we evaluated the antifungal and antibiofilm activity of riparin III (RIP3) against Trichophyton rubrum, Microsporum canis, and Nannizzia gypsea strains. We used ciclopirox (CPX) as a positive control. The effects of RIP3 on fungal growth were evaluated by the microdilution technique. The quantification of the biofilm biomass in vitro was assessed by crystal violet, and the biofilm viability was assessed by quantifying the CFU number. The ex vivo model was performed on human nail fragments, which were evaluated by visualization under light microscopy and by quantifying the CFU number (viability). Finally, we evaluated whether RIP3 inhibits sulfite production in T. rubrum. RIP3 inhibited the growth of T. rubrum and M. canis from 128 mg/L and N. gypsea from 256 mg/L. The results showed that RIP3 is a fungicide. Regarding antibiofilm activity, RIP3 inhibited biofilm formation and viability in vitro and ex vivo. Moreover, RIP3 inhibited the secretion of sulfite significantly and was more potent than CPX. In conclusion, the results indicate that RIP3 is a promising antifungal agent against biofilms of dermatophytes and might inhibit sulfite secretion, one relevant virulence factor.

Appraisal of selected ethnomedicinal plants as alternative therapies against onychomycosis: Evaluation of synergy and time-kill kinetics

Introduction: This study aims at the biological profiling of Allium sativum, Zingiber officinale, Nigella sativa, Curcuma longa, Mentha piperita, Withania somnifera, Azadirachta indica, and Lawsonia inermis as alternatives against onychomycosis to combat the treatment challenges. Methods: An extract library of aqueous (DW), ethyl acetate (EA), and methanol (M) extracts was subjected to phytochemical and antioxidant colorimetric assays to gauge the ameliorating role of extracts against oxidative stress. RP-HPLC quantified therapeutically significant polyphenols. Antifungal potential (disc diffusion and broth dilution) against filamentous (dermatophytes and non-dermatophytes) and non-filamentous fungi (yeasts; Candida albicans), synergistic interactions (checkerboard method) with terbinafine and amphotericin-B against resistant clinical isolates of dermatophytes (Trichophyton rubrum and Trichophyton tonsurans) and non-dermatophytes (Aspergillus spp., Fusarium dimerum, and Rhizopus arrhizus), time-kill kinetics, and protein estimation (Bradford method) were performed to evaluate the potential of extracts against onychomycosis. Results: The highest total phenolic and flavonoid content along with noteworthy antioxidant capacity, reducing power, and a substantial radical scavenging activity was recorded for the extracts of Z. officinale. Significant polyphenolics quantified by RP-HPLC included rutin (35.71 ± 0.23 µg/mgE), gallic acid (50.17 ± 0.22 µg/mgE), catechin (93.04 ± 0.43 µg/mgE), syringic acid (55.63 ± 0.35 µg/mgE), emodin (246.32 ± 0.44 µg/mgE), luteolin (78.43 ± 0.18 µg/mgE), myricetin (29.44 ± 0.13 µg/mgE), and quercetin (97.45 ± 0.22 µg/mgE). Extracts presented prominent antifungal activity against dermatophytes and non-dermatophytes (MIC-31.25 μg/ml). The checkerboard method showed synergism with 4- and 8-fold reductions in the MICs of A. sativum, Z. officinale, M. piperita, L. inermis, and C. longa extracts and doses of amphotericin-B (Amp-B) and terbinafine (against non-dermatophytes and dermatophytes, respectively). Furthermore, the synergistic therapy showed a time-dependent decrease in fungal growth even after 9 and 12 h of treatment. The inhibition of fungal proteins was also observed to be higher with the treatment of synergistic combinations than with the extracts alone, along with the cell membrane damage caused by terbinafine and amp-B, thus making the resistant fungi incapable of subsisting. Conclusion: The extracts of A. sativum, Z. officinale, M. piperita, L. inermis, and C. longa have proven to be promising alternatives to combat oxidative stress, resistance, and other treatment challenges of onychomycosis.

Itraconazole and Difluorinated-Curcumin Containing Chitosan Nanoparticle Loaded Hydrogel for Amelioration of Onychomycosis

Onychomycosis is a nail infection caused by a fungus, Trichophyton mentagrophytes, that is responsible for major nail infections. The best method suited for treating such infections generally includes a topical remedy. However, conventional oral or topical formulations are associated with various limitations. Therefore, a more efficient and compatible formulation is developed in this study. The primary objective of the current study is to formulate and evaluate chitosan nanoparticle-based hydrogel for ameliorating onychomycosis. The sole purpose of this research was to increase the permeation of the lipophilic drug itraconazole and difluorinated curcumin, and its synergistic antifungal activity was also evaluated for the first time. Both in vitro and ex vivo drug release evaluations confirmed the sustained release of both drugs from the hydrogel, which is a prerequisite for treating onychomycosis. The results overall highlighted the promising activity of a synergistic approach that could be implemented for the treatment of onychomycosis. The hydrogel-based formulation serves as an effective method of delivery of drugs across the layers of the skin, resulting from its hydrating characteristics.

Efficacy of Propolis Gel on Mature Biofilm Formed by Neocosmospora keratoplastica Isolated from Onychomycosis

This article describes Neocosmospora keratoplastica as an etiological onychomycosis agent. Ex vivo studies were initially performed to demonstrate the ability of this species to grow and form a well-organized characteristic biofilm on sterilized healthy nails. Based on the history of excellent results, both for antifungal and antibiofilm, of propolis resin gum, we evaluated its activity using artificially formed biofilm. In vitro, the minimal biofilm eradication concentration of the propolis extract (PE) was 375 µg of total polyphenol content (TPC) per mL, while for the propolis gel (PG) it was 450 µg of TPC per mL. In biofilm exposed to the propolis products, a decrease in hyphae and conidia was evident, accompanied by a disorganization of the extracellular matrix. Additionally, this low concentration of PE was able to significantly reduce the number of colony-forming units and the metabolic activity. Furthermore, the treatment of a 15-year nail infection due to N. keratoplastica was carried out exclusively using a topical treatment with a gel containing propolis (30%) with a daily dosage. This treatment achieved complete remission of the onychomycosis in 12 months. It is important to point out that some inconveniences previously reported by other patients treated with propolis extract were eliminated, increasing adherence to treatment.

Antifungal Activity of Amphiphilic Perylene Bisimides

Perylene-based compounds, either naturally occurring or synthetic, have shown interesting biological activities. In this study, we report on the broad-spectrum antifungal properties of two lead amphiphilic perylene bisimides, compounds 4 and 5, which were synthesized from perylene-3,4,9,10-tetracarboxylic dianhydride by condensation with spermine and an ammonium salt formation. The antifungal activity was evaluated using a collection of fungal strains and clinical isolates from patients with onychomycosis or sporotrichosis. Both molecules displayed an interesting antifungal profile with MIC values in the range of 2–25 μM, being as active as several reference drugs, even more potent in some particular strains. The ammonium trifluoroacetate salt 5 showed the highest activity with a MIC value of 2.1 μM for all tested Candida spp., two Cryptococcus spp., two Fusarium spp., and one Neoscytalidium spp. strain. Therefore, these amphiphilic molecules with the perylene moiety and cationic ammonium side chains represent important structural features for the development of novel antifungals.

Mixed Fungal Biofilms: From Mycobiota to Devices, a New Challenge on Clinical Practice

Most current protocols for the diagnosis of fungal infections are based on culture-dependent methods that allow the evaluation of fungal morphology and the identification of the etiologic agent of mycosis. Most current protocols for the diagnosis of fungal infections are based on culture-dependent methods that enable the examination of the fungi for further identification of the etiological agent of the mycosis. The isolation of fungi from pure cultures is typically recommended, as when more than one species is identified, the second agent is considered a contaminant. Fungi mostly survive in highly organized communities that provoke changes in phenotypic profile, increase resistance to antifungals and environmental stresses, and facilitate evasion from the immune system. Mixed fungal biofilms (MFB) harbor more than one fungal species, wherein exchange can occur that potentialize the effects of these virulence factors. However, little is known about MFB and their role in infectious processes, particularly in terms of how each species may synergistically contribute to the pathogenesis. Here, we review fungi present in MFB that are commensals of the human body, forming the mycobiota, and how their participation in MFB affects the maintenance of homeostasis. In addition, we discuss how MFB are formed on both biotic and abiotic surfaces, thus being a significant reservoir of microorganisms that have already been associated in infectious processes of high morbidity and mortality.

Insights on the etiopathogenesis of onychomycosis by dermatophyte, yeast and non dermatophyte mold in ex vivo model

Fungal biofilms have been involved in the pathogenesis of onychomycosis, but the aspects contributing to this association need to be enlightened. This study aimed to investigate the ability of three different fungi to form biofilm on the nail. All evaluated fungi were able to grow on the nails, using them as the only nutritional source and formed a structure strongly suggestive of biofilms. However, their architecture and morphology were highly contrasting: Candida albicans showed dense growth, exhibited a well-structured community and a large amount of extracellular matrix (ECM), and FTIR-ATR spectroscopy reinforced these findings revealing components suggestive of the biofilm. For Fusarium oxysporum these events were also observed, but in lower intensity. Furthermore, while Trichophyton rubrum presented a well-organized architecture, the ECM was not visualized. We hypothesize that these findings are related to the symptomatology of onychomycosis. When it is caused by a non-dermatophyte, it usually is accompanied with paronychia, pain, edema, inflammation and few signals of keratolysis, while dermatophytes are more associated with intense onycholysis and absence of the inflammatory signals. Biofilm seems to be crucial for non-dermatophytes to cause onychomycosis, but not for T. rubrum.