Trichophyton rubrumDNA strain switching increases in patients with onychomycosis failing antifungal treatments

Metagenomics of Toenail Onychomycosis in Three Victorian Regions of Australia

Onychomycosis is a fungal disease of the nail that is found worldwide and is difficult to diagnose accurately. This study used metagenomics to investigate the microbiology of 18 clinically diagnosed mycotic nails and two normal nails for fungi and bacteria using the ITS2 and 16S loci. Four mycotic nails were from Bass Coast, six from Melbourne Metropolitan and eight from Shepparton, Victoria, Australia. The mycotic nails were photographed and metagenomically analysed. The ITS2 sequences for T. rubrum and T. interdigitale/mentagrophytes averaged over 90% of hits in 14/18 nails. The high abundance of sequences of a single dermatophyte, compared to all other fungi in a single nail, made it the most likely infecting agents (MLIA). Trichophyton rubrum and T. interdigitale/mentagrophytes were found in Bass Coast and Shepparton while only T. interdigitale/mentagrophytes was found in Melbourne. Two nails with T. interdigitale/mentagrophytes mixed with high abundance non-dermatophyte moulds (NDMs) (Aspergillus versicolor, Acremonium sclerotigenum) were also observed. The two control nails contained chiefly Fusarium oxysporum and Malassezia slooffiae. For bacteria, Staphylococcus epidermidis was in every nail and was the most abundant, including the control nails, with an overall mean rate of 66.01%. Rothia koreensis, Corynebacterium tuberculostearicum, and Brevibacterium sediminis also featured.

Anti-dermatophyte activity of the aqueous extracts of Thai medicinal plants

Medicinal plants have long been prescribed in Thailand for centuries. Different constituents of extracts have been used for treating of various infectious diseases. However, there is even less information available regarding the use in fungal skin infection. In order to assess traditional Thai claims about the therapeutic potential, this study is focused on exploring the anti-dermatophyte property of the plants that are currently used as traditional medicines. The potential of four different plant species were selected for investigate in vitro anti-dermatophyte activity. Ethanolic extracts of Chromolaena odorata (L.), Ageratina adenophora (Spreng.), Eclipta prostrate (Linn.), and Acorus calamus (L.). were analysed for their total phenolic content as well as total flavonoid content and were then subjected to test of their anti-dermatophyte properties using agar well diffusion method. Qualitative flavonoids and phenolics analysis of the extracts showed their biologically active constituents. Among the species examined, the result indicated that most of the extracts demonstrated anti-dermatophyte activity. In particular, A. calamus showed the highest efficacy against test organisms. The experiment confirmed the chemical constituents and efficacy of some selected plants and provides a scientific confirmation of the use of Thai plants in traditional medicine for fungal skin infections.

A Paradigm Shift in the Treatment and Management of Onychomycosis

There is an increase in the incidence of onychomycosis, especially in at-risk populations. Onychomycosis is difficult to treat, as the efficacy of most antifungal agents is relatively low. Nondermatophyte molds (NDMs) and mixed infection (dermatophyte plus NDM) onychomycosis are contributing to growing antifungal resistance, as they are often underestimated and ignored due to incorrect diagnosis. There is a need for a paradigm shift in the management of onychomycosis to a patient-centered, holistic approach with an emphasis on laboratory diagnosis prior to initiating treatment, which enables the rational choice of the antifungal agent. Additionally, in the case of resistant infections, antifungal susceptibility testing is recommended. Strategies for effective management of onychomycosis include disinfection of fungal reservoirs in shoes and socks and prophylaxis posttreatment using topical antifungal agents. These measures may reduce the recurrence of onychomycosis and improve long-term clinical success.

The increasing problem of treatment-resistant fungal infections: a call for antifungal stewardship programs

Antimicrobial stewardship (AMS) programs have been widely recognized among the public health community. These programs focus majorly on bacterial infections, efficient antibiotic use, and measures to curb increasing antibacterial resistance. AMS programs are successfully established around the globe; however, very few include antifungal stewardship (AFS). The increasing incidence of superficial and invasive fungal infections, combined with delayed or inaccurate diagnosis, has contributed to the overprescribing and overuse of antifungal agents. Such increased exposure to antifungal agents may be a reason for the emergence of increasing antifungal resistance among fungal pathogens. With mounting reports of treatment failures and resistant infections, the evidence to support the need for AFS programs is increasing. AFS is an emerging branch of AMS programs that requires global attention and recognition.

Trichophyton rubrum DNA Strains in Patients with Onychomycosis with Persistent Mixed Infections Involving a Nondermatophyte Mold

BACKGROUND

Onychomycosis is estimated to occur in approximately 10% of the global population, with most cases caused by Trichophyton rubrum. Some persistent onychomycosis is caused by mixed infections of T rubrum and one or more co-infecting nondermatophyte molds (NDMs). In onychomycosis, T rubrum strain types may naturally switch and may also be triggered to switch in response to antifungal therapy. T rubrum strain types in mixed infections of onychomycosis have not been characterized.

METHODS

T rubrum DNA strains in mixed infections of onychomycosis containing co-infecting NDMs were compared with a baseline North American population through polymerase chain reaction amplification of ribosomal DNA tandemly repetitive subelements (TRSs) 1 and 2. The baseline DNA strain types were determined from 102 clinical isolates of T rubrum. The T rubrum DNA strain types from mixed infections were determined from 63 repeated toenail samples from 15 patients.

RESULTS

Two unique TRS-2 types among the clinical isolates contributed to four unique TRS-1 and TRS-2 strain types. Six TRS-1 and TRS-2 strain types represented 92% of the clinical isolates of T rubrum. Four TRS-1 and TRS-2 strain types accounted for 100% of the T rubrum within mixed infections.

CONCLUSIONS

Four unique North American T rubrum strains were identified. In support of a shared ancestry, the T rubrum DNA strain types found in mixed infections with NDMs were among the most abundant types. A population of T rubrum strains in mixed infections of onychomycosis has been characterized, with more than one strain detected in some nails. The presence of a co-infecting NDM in mixed infections may contribute to failed therapy by stabilizing the T rubrum strain type, possibly preventing the antifungal therapy-induced strain type switching observed with infections caused by T rubrum alone.

High prevalence of mixed infections in global onychomycosis

Onychomycosis is estimated at a prevalence of 10% worldwide with the infecting organism most commonly Trichophyton rubrum (T. rubrum). Traditional culture identification of causative organisms has inherent risks of overestimating dermatophytes, like T. rubrum, by inhibiting the growth of possible nondermatophyte mould (NDM) environmental contaminants which could be causative agents. Recently, molecular methods have revealed that a proportion of onychomycosis cases in North America may be caused by mixed infections of T. rubrum as an agent co-infecting with one or more NDM. Determining the global burden of mixed infections is a necessary step to evaluating the best therapies for this difficult-to-treat disease. To determine the prevalence of mixed infections in a global population, nail samples from onychomycosis patients in Brazil, Canada, and Israel (n = 216) were analyzed by molecular methods for the presence of dermatophytes and five NDMs. If an NDM was detected, repeat sampling was performed to confirm the NDM. T. rubrum was detected in 98% (211/216) of infections with 39% mixed (84/216). The infection type was more likely to be mixed in samples from Brazil, but more likely to be a dermatophyte in samples from Canada and Israel (Χ² = 16.92, df = 2, P<0.001). The most common cause of onychomycosis was T. rubrum. In all countries (Brazil, Canada and Israel combined) the prevalence of dermatophyte (Χ² = 211.15, df = 3, P<0.001) and mixed (dermatophyte and NDM; Χ² = 166.38, df = 3, P<0.001) infection increased with patient age. Our data suggest that mixed infection onychomycosis is more prevalent than previously reported with the aging population being at increased risk for mixed infections.

A Practical Guide to Curing Onychomycosis: How to Maximize Cure at the Patient, Organism, Treatment, and Environmental Level

Onychomycosis is a fungal nail infection caused by dermatophytes, non-dermatophyte molds, and yeasts. Treatment of this infection can be difficult, with relapse likely to occur within 2.5 years of cure. The objective of this article is to review factors that can impact cure and to suggest practical techniques that physicians can use to maximize cure rates. Co-morbidities, as well as disease severity and duration, are among the many patient factors that could influence the efficacy of antifungal therapies. Furthermore, organism, treatment, and environmental factors that may hinder cure include point mutations, biofilms, affinity for non-target enzymes, and exposure to fungal reservoirs. To address patient-related factors, physicians are encouraged to conduct confirmatory testing and treat co-morbidities such as tinea pedis early and completely. To combat organism-focused factors, it is recommended that disruption of biofilms is considered, and drugs with multiple routes of delivery and unique mechanisms of action are prescribed when traditional agents are not effective. Extending follow-up periods, using combination treatments, and considering pulse regimens may also be of benefit. Through these practical techniques, physicians can maximize cure and limit the risk of relapse and re-infection.

Circadian Rhythm, and Antimicrobial and Anticholinesterase Activities of Essential Oils from Vitex gardneriana

Vitex gardneriana, popularly known as “jaramataia”, is a shrub commonly found in the caatinga biome located in northeast Brazil. In folk medicine, its leaves have been used as analgesic and anti-inflammatory agents. Here we describe, for the first time, the chemical composition of the leaf essential oils extracted at 8.00, 12.00 and 17.00 h from V. gardneriana and report on their circadian rhythm, and antimicrobial and anticholinesterase activities. The essential oils’ antifungal activity was evaluated by a broth microdilution method using strains of dermatophytes, fungi and yeasts. The modulatory activity assays were performed by the checkerboard technique using ketoconazole as a standard drug, and acetylcholinesterase inhibitory activity was performed using Ellman's colorimetric method and compared with a reference acetycholinesterase inhibitor (physostigmine). The essential oils extracted from the leaves were analyzed by GC/MS and GC/FID. Twenty-five constituents (94.7%) were identified in the 8 o'clock oil, these being 2 monoterpenes (0.4%) and 23 sesquiterpenes (94.3%). For the essential oil extracted at 12 o'clock, 26 constituents (91.8%) were identified, of which 2 were monoterpenes (0.3%) and 24 sesquiterpenes (91.5%). For the essential oil extracted at 17.00 h, 32 constituents (91.4%) were identified, of which 5 were monoterpenes (3.4%) and 27 sesquiterpenes (88%). The main constituents of the 8.00, 12.00 and 17.00 h essential oils were the sesquiterpenes cis-calamenene (27.9, 24.5 and 25.8%), 6,9-guaiadiene (21.8, 11.2 and 18.4%) and caryophyllene oxide (16.7, 26.3 and 13.8%), respectively. The essential oils showed activity against strains of Trichophyton rubrum.

Single-nucleotide polymorphism in a local population of Trichophyton rubrum

Trichophyton rubrum is an important causative agent of superficial mycoses worldwide. To uncover a genetic composition of a local population of this fungus, we sequenced A7C99_6411 and A7C99_6714 loci, coding for hypothetical proteins and revealed two complex genotypes, differing by a single missense mutation in each locus. One of the two A7C99_6411/6714 genotypes was not found in tinea pedis cases and demonstrated mostly longer TRS-1 elements when compared to another genotype. Thus, we present a description of nucleotide polymorphism in protein-coding loci in T. rubrum and provide evidence for ecological preferences of T. rubrum genotypes at a local scale.

Overview of selected virulence attributes in Aspergillus fumigatus, Candida albicans, Cryptococcus neoformans, Trichophyton rubrum, and Exophiala dermatitidis

The incidence of fungal diseases has been increasing since 1980, and is associated with excessive morbidity and mortality, particularly among immunosuppressed patients. Of the known 625 pathogenic fungal species, infections caused by the genera Aspergillus, Candida, Cryptococcus, and Trichophyton are responsible for more than 300 million estimated episodes of acute or chronic infections worldwide. In addition, a rather neglected group of opportunistic fungi known as black yeasts and their filamentous relatives cause a wide variety of recalcitrant infections in both immunocompetent and immunosuppressed hosts. This article provides an overview of selected virulence factors that are known to suppress host immunity and enhance the infectivity of these fungi.

Molecular Markers Useful for Intraspecies Subtyping and Strain Differentiation of Dermatophytes

Dermatophytosis is a very common skin disorder and the most frequent infection encountered by practicing dermatologists. The identification, pathogenicity, biology, and epidemiology of dermatophytes, the causative agents of dermatophytosis, are of interest for both dermatologists and medical mycologists. Recent advances in molecular methods have provided new techniques for identifying dermatophytes, including intraspecies variations. Intraspecies subtyping and strain differentiation have made possible the tracking of infections, the identification of common sources of infections, recurrence or reinfection after treatment, and analysis of strain virulence and drug resistance. This review describes molecular methods of intraspecies subtyping and strain differentiation, including analyses of mitochondrial DNA and non-transcribed spacer regions of ribosomal RNA genes, random amplification of polymorphic DNA, and microsatellite markers, along with their advantages and limitations.

Gene Expression Response of Trichophyton rubrum during Coculture on Keratinocytes Exposed to Antifungal Agents

Trichophyton rubrum is the most common causative agent of dermatomycoses worldwide, causing infection in the stratum corneum, nails, and hair. Despite the high prevalence of these infections, little is known about the molecular mechanisms involved in the fungal-host interaction, particularly during antifungal treatment. The aim of this work was to evaluate the gene expression of T. rubrum cocultured with keratinocytes and treated with the flavonoid trans-chalcone and the glycoalkaloid α-solanine. Both substances showed a marked antifungal activity against T. rubrum strain CBS (MIC = 1.15 and 17.8 µg/mL, resp.). Cytotoxicity assay against HaCaT cells produced IC50 values of 44.18 to trans-chalcone and 61.60 µM to α-solanine. The interaction of keratinocytes with T. rubrum conidia upregulated the expression of genes involved in the glyoxylate cycle, ergosterol synthesis, and genes encoding proteases but downregulated the ABC transporter TruMDR2 gene. However, both antifungals downregulated the ERG1 and ERG11, metalloprotease 4, serine proteinase, and TruMDR2 genes. Furthermore, the trans-chalcone downregulated the genes involved in the glyoxylate pathway, isocitrate lyase, and citrate synthase. Considering the urgent need for more efficient and safer antifungals, these results contribute to a better understanding of fungal-host interactions and to the discovery of new antifungal targets.