An update on antifungal resistance in dermatophytosis

Efficient extraction of Licochalcone a with deep eutectic solvent: A promising drug for the treatment of dermatophytosis

Uncontrolled breeding and improper management of pet cats and dogs have led to the spread of zoonotic Microsporum canis (M. canis) infection, which poses challenges to clinical medication. Therefore, there is an urgent need to explore and discover potential fungicides against M. canis. In this study, licochalcone A (LicoA) was prepared by a green and efficient deep eutectic solvent method based on ultrasonic assisted extraction (DES-UAE). The DES-UAE process with choline chloride and propionic acid as solvent was optimized by response surface method with the extraction amount of LicoA as the objective. Following separation and purification, the purity of LicoA reached 99.79 %. Additionally, LicoA demonstrated significant antifungal activity against M. canis with MIC of 4 μg/mL. LicoA inhibited the synthesis of ergosterol in the fungal membrane, destroy the integrity of the cell membrane, lead to the increase of membrane permeability, the release of intracellular electrolytes, the leakage of nucleic acids and proteins, and affect the normal growth of hyphae. ATPase activity was reduced, and mitochondrial membrane potential (MMP) was reduced, resulting in increased levels of ROS, which eventually induced apoptosis in M. canis. Further transcriptome analysis revealed that LicoA treatment affected "cell integrity", "energy metabolism", and "oxidative stress" metabolic pathways in M. canis, including cell wall synthesis, ergosterol synthesis, tricarboxylic acid cycle, electron transport chain, and ribosome metabolism, leading to fungal cell apoptosis. These studies establish an efficient method for LicoA extraction and provide a basis for its use as a novel antifungal agent for the treatment of dermatophytosis.

Terbinafine Resistance in Trichophyton rubrum and Trichophyton indotineae: A Literature Review

BACKGROUND/OBJECTIVES

Terbinafine has been the gold standard for the management of superficial fungal infections. The etiological agent generally is Trichophyton rubrum (T. rubrum); however, there has been increased reporting of a new terbinafine-resistant strain of the T. mentagrophytes complex (T. mentagrophytes ITS genotype VIII otherwise known as T. indotineae). Here, we review the epidemiology, clinical features, diagnosis, and treatment of T. rubrum and T. indotineae infections.

METHODS

We conducted a systematic literature search using PubMed, Embase (Ovid), and Web of Science, resulting in 83 qualified studies with data summarized for clinical features, antifungal susceptibility, and terbinafine resistance mechanisms and mutations.

RESULTS

Dermatophytosis is most commonly caused by T. rubrum; however, in certain parts of the world, especially in the Indian subcontinent, T. indotineae infections have been reported more frequently. The majority of T. rubrum isolates remain susceptible to terbinafine (over 60% of isolates show MIC50 and MIC90 < 0.5 µg/mL). In contrast, for T. indotineae, 30% of isolates exhibit MIC50 ≥ 0.5 µg/mL and 80% exhibit MIC90 ≥ 0.5 µg/mL. Frequently detected squalene epoxidase (SQLE) mutations in T. rubrum are Phe397Leu/Ile (41.6%) and Leu393Phe (20.8%); in T. indotineae, these include Phe397Leu (33.0%) and Ala448Thr (24.5%). Other potential terbinafine resistance mechanisms in T. rubrum and T. indotineae are discussed.

CONCLUSIONS

T. rubrum generally remain susceptible in vitro to terbinafine in contrast to T. indotineae. The essential components of an effective antifungal stewardship emphasize accurate clinical and laboratory diagnosis, susceptibility testing, and appropriate antifungal therapy selection with a multidisciplinary approach.

Patients knowledge attitudes and practices regarding superficial fungal infections suggest public health and patient education are warranted

Superficial fungal infections are common worldwide and significantly impact public health. Understanding patients' knowledge, attitudes, and practices (KAP) regarding their treatment and prognosis is essential for addressing gaps in care. This cross-sectional study utilized a self-designed KAP questionnaire to assess 456 patients with superficial fungal infections between October 15, 2023, and March 15, 2024. Data analysis included descriptive statistics, logistic regression, and structural equation modeling. The mean scores for knowledge, attitudes, and practices were 14.85 ± 7.75, 27.01 ± 4.28, and 22.91 ± 4.17, respectively. Key findings revealed that 32% of patients were unsure about long-term treatment, 51% misunderstood corticosteroid use, and 69% believed medications could be stopped once symptoms improved. Significant demographic disparities in KAP scores were observed, highlighting the influence of gender, age, education, and income. Patients exhibit inadequate knowledge, predominantly negative attitudes, and suboptimal practices regarding superficial fungal infections. Targeted educational interventions are crucial for enhancing treatment adherence, addressing misconceptions, and reducing antifungal resistance.

First Report of Trichophyton indotineae Infection in Hungary

Trichophyton indotineae is associated with difficult-to-treat, often extensive dermatophytosis and resistance to the commonly used antifungal agents. Successful therapy often necessitates higher than usual doses of systemic therapy for prolonged periods. The spread of this species has gained much attention lately, as several European and other Western hemisphere countries have recently reported their first respective cases or increasing numbers of them. Until recently, this species was not described in Hungary. Here, we report a case caused by this species in a patient with a travel history to an endemic region. The isolate was identified preliminarily by MALDI-TOF mass spectrometry and confirmed by DNA sequencing; furthermore, it was subject to phenotypic antifungal susceptibility testing by broth microdilution to fluconazole, voriconazole, posaconazole, itraconazole, and terbinafine. According to the susceptibility results, the isolate was wild type to all tested agents, including terbinafine which was in line with the sequencing data, and with the uncommon excellent therapeutic response to topical allylamine treatment. This case also further confirms the applicability of the MSI-2 database for the rapid identification of T. indotineae in routine clinical microbiology laboratories as a cost-effective and simple method.

Demographic and Pathogen Profiles of Superficial Fungal Infections-A Single-Centre Observational Study in Poland

BACKGROUND

Superficial fungal infections (SFI) are contagious conditions affecting the skin and its appendages, caused by various fungal species. Monitoring the distribution of common pathogens and identifying at-risk patient groups are essential for effective management and prevention.

OBJECTIVES

This study investigates the characteristics of SFI in Poland's Malopolska region from 2017 to 2019, focusing on etiological agents, infection sites and risk factors.

PATIENTS/METHODS

A retrospective analysis was conducted on 4522 mycological cultures from 3594 patients, incorporating demographic data (age, sex), sample sites and mycological test results.

RESULTS

Among the 1175 positive mycological tests recorded from 959 patients, Trichophyton rubrum-primarily affecting toenails and feet-and Candida albicans-mainly targeting fingernails-were the most common pathogens across all age groups. Children exhibited a higher incidence of infections caused by Microsporum canis, Malassezia furfur and T. mentagrophytes. In contrast, Scopulariopsis brevicaulis was more frequently identified in individuals over 60 years old.

CONCLUSIONS

The observed trends in SFI characteristics at our centre during the pre-pandemic period align with global epidemiological data. However, further studies are warranted to address existing gaps in understanding the epidemiology of SFI and to refine preventive and therapeutic strategies.

New Sources of Resistance to Terbinafine Revealed and Squalene Epoxidase Modelled in the Dermatophyte Fungus Trichophyton interdigitale From Australia

BACKGROUND

Terbinafine is widely used to treat onychomycosis caused by dermatophyte fungi. Terbinafine resistance in recent years is causing concern. Resistance has so far been associated with single-nucleotide substitutions in the DNA sequence of the enzyme squalene epoxidase (SQLE) but how this affects SQLE functionality is not understood.

OBJECTIVES

The aim of this study was to understand newly discovered resistance in two Australian strains of Trichophyton interdigitale.

PATIENTS/METHODS

Resistance to terbinafine was tested in four newly isolated strains. Three-dimensional SQLE models were prepared to investigate how the structure of their SQLE affected the binding of terbinafine.

RESULTS

This study found the first Australian occurrences of terbinafine resistance in two T. interdigitale strains. Both strains had novel deletion mutations in erg1 and frameshifts during translation. Three-dimensional models had smaller SQLE proteins and open reading frames as well as fewer C-terminal α-helices than susceptible strains. In susceptible strains, the lipophilic tail of terbinafine was predicted to dock stably into a hydrophobic pocket in SQLE lined by over 20 hydrophobic amino acids. In resistant strains, molecular dynamics simulations showed that terbinafine docking was unstable and so terbinafine did not block squalene metabolism and ultimately ergosterol production. The resistant reference strain ATCC MYA-4438 T. rubrum showed a single erg1 mutation that resulted in frameshift during translation, leading to C-terminal helix deletion.

CONCLUSIONS

Modelling their effects on their SQLE proteins will aid in the design of potential new treatments for these novel resistant strains, which pose clinical problems in treating dermatophyte infections with terbinafine.