In Vitro Antifungal Susceptibility Profiles of 12 Antifungal Drugs against 55 Trichophyton schoenleinii Isolates from Tinea Capitis Favosa Patients in Iran, Turkey, and China

Tinea capitis due to Microsporum ferrugineum: A case of unusual laboratory finding on direct microscopic examination of infected hairs and skin lesions

Tinea capitis is a chronic fungal infection of the scalp occurring commonly in children of school age, especially in developing countries. It is caused primarily by the dermatophyte members of genera Microsporum and Trichophyton. Here we report presence of free-living mycelial stage of dermatophytes, a stage of fungal growth which form in culture medias, around affected hairs and skin scrapings of scalp lesions in a 3-year-old boy presenting with alopecia and multiple scaly, non-erythematous plaques. On direct microscopy examination using 10 % potassium hydroxide, the fungal hyphae and arthrospores were detected in ectothrix form. In addition, we also observed numerous multicellular, thick-walled spindle-shaped macroconidia around hairs and skin scrapings. To our knowledge this is the first study reporting dermatophyte's macroconidia directly seen on clinical samples. Species level identification of the dermatophyte isolate growing on Mycosel™ agar was confirmed by PCR-sequencing of internal transcribed spacer of ribosomal RNA as Microsporum ferrugineum. The patient was successfully treated with systemic itraconazole combined with topical ketoconazole shampoo.

Iranian National Survey on Tinea Capitis: Antifungal Susceptibility Profile, Epidemiological Characteristics, and Report of Two Strains with a Novel Mutation in SQLE Gene with Homology Modeling

BACKGROUND

The data on the epidemiological and antifungal susceptibility profile of tinea capitis (TC) in Iran has not been updated in recent decades. This report presents the Iranian epidemiological and drug susceptibility data regarding the distribution of dermatophytes species isolated by six national mycology centers for a period of one year (2020-2021).

MATERIAL AND METHODS

A total of 2100 clinical samples from individuals suspeted to TC were subjected to mycological analysis of direct microscopy and culture. For definite species identification, the culture isolates were additionally subjected to PCR-RFLP and PCR-sequencing of the ITS ribosomal DNA (ITS-rDNA) region. Antifungal susceptibility profiles for eight common antifungal drugs were determined by CLSI M38-A3 guidelines. The SQLE gene was partially amplified and sequenced in two terbinafine-resistant and two susceptible T. mentagrophytes isolates to elucidate probable substitutions involved in resistance.

RESULTS

TC (n = 94) was diagnosed in 75 children (79.8%) and 19 adults (20.2%) by direct microscopy and culture. Frequency of TC was significantly more among males (66 males = 70.2% vs 28 females = 29.8%). The prevalent age group affected was 5-9 years (39.36%). Thirty-two (34.04%) T. mentagrophytes, 27 (28.7%) T. tonsurans, 14 (14.9%) M. canis, 13 (13.8%) T. violaceum, 5 (5.32%) T. indotineae, 2 (2.1%) T. benhamiae, and 1 (1.1%) T. schoenleinii were identified as the causative agents. MIC values of isolates showed susceptibility to all antifungal agents, except for fluconazole and griseofulvin with GM MIC of 11.91 μg/ml and 2.01 μg/ml, respectively. Terbinafine exhibited more activity against isolates, with GM MIC 0.084 μg/ml followed by ketoconazole (0.100 μg/ml), econazole (0.107 μg/ml), itraconazole (0.133 μg/ml), butenafine (0.142 μg/ml), and miconazole (0.325 μg/ml). Two resistant T. mentagrophytes isolates harbored missense mutations in SQLE gene, corresponding to amino acid substitution F397L. Remarkably, one unique mutation, C1255T, in the SQLE sequence of two terbinafine-susceptible T. mentagrophytes strains leading to a change of leucine at the 419th position to phenylalanine (L419F) was detected.

CONCLUSIONS

T. mentagrophytes, T. tonsurans, and M. canis remained the main agents of TC in Iran, however less known species such as T. indotinea and T. benhamiae are emerging as new ones. Terbinafine could still be the appropriate choice for the treatment of diverse forms of TC.

The in vitro Activity of Echinocandins Against Clinical Trichophyton rubrum Isolates and Review of the Susceptibility of T. rubrum to Echinocandins Worldwide

Introduction

The emergence of resistance in Trichophyton rubrum to azoles and terbinafine has become increasingly evident in recent years, necessitating the development of novel antifungal drugs and the exploration of new indications for existing agents.

Methods

In this study, we retrospectively evaluated the in vitro antifungal activity of 3 echinocandins (anidulafungin, caspofungin, and micafungin) against 73 clinical isolates of T. rubrum collected from a teaching hospital in Shanghai, China, using EUCAST E.DEF 9.3.1 with minor modification. We also reviewed the susceptibility of T. rubrum to echinocandins globally by literature searching.

Results

Our findings revealed that micafungin exhibited the lowest modal minimum effective concentration (MEC) value (0.08 mg/L, n = 28) and the lowest geometric mean (GM) MEC value (0.014 mg/L) among the 73 isolates of T. rubrum tested, followed by anidulafungin with a modal MEC value of 0.016 mg/L (n = 67) and a GM of 0.018 mg/L. Caspofungin displayed a higher modal MEC value of 0.5 mg/L (n = 35) and a GM of 0.308 mg/L. Despite variations in methodologies, similar results were obtained from the review of five relevant studies included in our analysis.

Discussion

Echinocandins exhibited excellent in vitro activity against T. rubrum isolates, with micafungin and anidulafungin demonstrating greater potency than caspofungin. These findings suggest that echinocandins could be considered as potential treatment options for managing recalcitrant dermatophytoses resulting from the emergence of resistance. However, it is important to note that the clinical efficacy of these in vitro findings has yet to be established and warrants further investigation.

Molecular Mechanisms of 5-Fluorocytosine Resistance in Yeasts and Filamentous Fungi

Effective management and treatment of fungal diseases is hampered by poor diagnosis, limited options for antifungal therapy, and the emergence of antifungal drug resistance. An understanding of molecular mechanisms contributing to resistance is essential to optimize the efficacy of currently available antifungals. In this perspective, one of the oldest antifungals, 5-fluorocytosine (5-FC), has been the focus of recent studies applying advanced genomic and transcriptomic techniques to decipher the order of events at the molecular level that lead to resistance. These studies have highlighted the complexity of resistance and provided new insights that are reviewed in the present paper.

Molecular Identification and Antifungal Susceptibility Patterns of Dermatophytes Isolated from Companion Animals with Clinical Symptoms of Dermatophytosis

Introduction

Dermatophytosis is a common skin disease in cats and dogs caused by Microsporum and Trichophyton fungi. Species identification and knowledge of their antifungal susceptibility are therapeutically and epidemiologically important. This study assessed the prevalence of feline and canine dermatophytosis in Iran, identified the aetiological agents molecularly and tested their antifungal susceptibility.

Material and Methods

A total of 308 companion animals (134 dogs and 174 cats) with skin lesions were examined from March 2015 to March 2018. Hair and skin samples were examined by microscopy with 20% KOH and cultured on Sabouraud dextrose agar with cycloheximide and chloramphenicol. Fungal isolates were confirmed by sequencing of the internal transcribed spacer (ITS) r-DNA region. The antifungal susceptibility of dermatophytes was tested by broth microdilution assay using standard drugs.

Results

Dermatophytes were found in 130 (42.2%) samples, 62 of them feline and 68 canine. Based on sequencing of all strains, M. canis (78.5%, P<0.05), M. gypseum (10.7%), and T. mentagrophytes (10.7%) were the dermatophytes isolated. The non-dermatophyte species Nannizziopsis vriesii was also isolated from two feline dermatomycosis cases. Dogs and cats younger than one year (61.5%) showed a statistically significantly higher prevalence of infection (P<0.05). Caspofungin produced the lowest geometric mean MIC at 0.0018 μg/mL, followed by ketoconazole, terbinafine, itraconazole, miconazole, griseofulvin, clotrimazole and fluconazole, in a 0.038–1.53 μg/mL range.

Conclusion

This is the first molecular study to identify the causes of pet dermatophytosis in north-western Iran. ITS-PCR was shown to be a useful and reliable method for the identification of closely related species of dermatophytes in clinical and epidemiological settings. The lowest MIC of caspofungin indicated that this drug was the most potent in vitro.

In vitro antifungal susceptibility patterns of Trichophyton benhamiae complex isolates from diverse origin

BACKGROUND

Species from the Trichophyton benhamiae complex are mostly zoophilic dermatophytes which cause inflammatory dermatophytosis in animals and humans worldwide.

OBJECTIVES

This study was purposed to (a) to identify 169 reference and clinical dermatophyte strains from the T benhamiae complex species by molecular method and adhering to the newest taxonomy in the complex (b) to evaluate the in vitro antifungal susceptibility profile of these strains against eight common and new antifungal agents that may be used for the treatment of dermatophytosis.

METHODS

All isolates, mainly originated from Europe but also from Iran, Japan and USA, were subjected to ITS-rDNA sequencing. The in vitro antifungal susceptibility profiles of eight common and new antifungal drugs against the isolates were determined by CLSI M38-A2 protocol and according to microdilution method.

RESULTS

Based on the ITS-rDNA sequencing, T benhamiae was the dominant species (n = 102), followed by T europaeum (n = 29), T erinacei (n = 23), T japonicum (n = 10), Trichophyton sp (n = 4) and T eriotrephon (n = 1). MIC ranges across all isolates were as follows: luliconazole: 0.0002-0.002 µg/ml, terbinafine: 0.008-0.125 µg/ml, efinaconazole: 0.008-0.125 µg/ml, ciclopirox olamine: 0.03-0.5 µg/ml, itraconazole: 0.06-2 µg/ml, griseofulvin: 0.25-4 µg/ml, amorolfine hydrochloride: 0.125-4 µg/ml and tavaborole: 1-16 µg/ml.

CONCLUSION

Luliconazole, efinaconazole and terbinafine were the most potent antifungals against T benhamiae complex isolates, regardless of the geographic locations where strains were isolated. These data might help dermatologists to develop effective therapies for successful treatment of infections due to T benhamiae complex species.

Familial Cases of Trichophyton benhamiae Infection Transmitted from a Guinea Pig in Iran

Trichophyton benhamiae is a zoophilic dermatophyte mainly transmitted to humans from guinea pigs. This zoophilic species can also cause dermatophytosis as reported by human contact with other animals, such as rabbit, cat, and fox. Here, we report the tinea faciei and tinea corporis cases: a 12-year-old girl and her 53-year-old father, with no history of immunodeficiency and underlying disease, caused by T. benhamiae transmitted from a guinea pig in Iran. Dermatological examination revealed several erythematous, round, scaly, and approximately 1-4-cm-diameter lesions in both patients. The girl had seven skin lesions, and her father presented two skin lesions on the front side of his neck. The girl's lesions had started 3 weeks before and her father's lesions appeared 7 days after the first clinical appearance of the lesions in the daughter. The girl had daily close contact with a guinea pig, while her father did not have any direct exposure to the pet. Examination of the lesions scraping with 10% potassium hydroxide (KOH 10%) revealed hyaline septate hyphae and arthroconidia. The dermatophyte isolated in culture was identified as T. benhamiae using molecular analysis. The patients were successfully treated using topical sertaconazole nitrate 2% cream twice a day for 4 weeks.

Molecular identification and antifungal susceptibility among clinical isolates of dermatophytes in Shiraz, Iran (2017-2019)

Dermatophytosis is a common superficial mycotic infection affecting individual's quality of life worldwide. The present study aimed to perform species-level identification and evaluate the antifungal susceptibility patterns of dermatophytes isolated in Shiraz, Iran. This cross-sectional study was conducted on clinical samples collected during 2017-2019 from 307 patients suspected of having dermatophytosis. The isolates were identified by direct microscopy, culture and internal transcribed spacer ribosomal DNA sequencing, and their antifungal susceptibility patterns were determined by the microdilution method. Among 307 patients, dermatophytosis was diagnosed by microscopy in 190 (61.8%) subjects and confirmed in 130 (42.3%) cases by both microscopy and culture. It was found out tinea pedis was the most common clinical manifestation, and Trichophyton mentagrophytes was the most prevalent species (28.4%), followed by T tonsurans (23.8%), Microsporum canis (11.5%), T interdigitale (10%), T verrucosum (6.9%), T rubrum (6.9%), T benhamiae (4.6%), T violaceum (3%), T simii (3%), Epidermophyton floccosum (0.7%) and M ferrugineum (0.7%). Moreover, it was revealed that luliconazole with a geometric mean (GM) minimum inhibitory concentration (MIC) of 0.03 μg ml^-1 was the most effective agent against all tested isolates. Regardless of species, 30% of isolates responded to high MICs of griseofulvin (MIC₉₀  > 2 μg ml^-1 ). The increasing prevalence of nonindigenous species of T simii, T benhamiae and M ferrugineum in Shiraz, Iran, was a notable finding. In addition, infections due to zoophilic species showed an increasing trend. These epidemiological data, along with antifungal susceptibility patterns, may have implications for clinical decision-making and successful treatment.

Investigation of in vitro antifungal susceptibility testing and genetic diversity of clinical isolates of Trichophyton benhamiae and Trichophyton eriotrephon in Iran

BACKGROUND

Trichophyton benhamiae is a zoophilic dermatophyte, known as one of the causative agents of dermatophytosis.

OBJECTIVES

The purpose of this study was to explore the genotypes of T. benhamiae strains isolated from geographically different areas of Iran and also to evaluate in vitro antifungal susceptibility profile of these strains against seven antifungal drugs.

METHODS

Twenty-two strains of T. benhamiae and two strains of T. eriotrephon were isolated from patients with distinct types of dermatophytosis. DNA extraction and amplification of rDNA regions using ITS1 and ITS4 primers were conducted on the isolates. The in vitro antifungal susceptibility of posaconazole (PSC), voriconazole (VRC), itraconazole (ITC), ketoconazole (KET), caspofungin (CAS), terbinafine (TRB) and griseofulvin (GRZ) was evaluated according to CLSI M38-A2 protocol.

RESULTS

The multiple alignment of the ITS-rDNA sequences of T. benhamiae indicated a mean similarity of 99.5%, with 0-3 interspecies nucleotide difference. The geometric mean (GM) values of minimum inhibitory concentrations (MICs) and minimum effective concentrations (MECs) across the all isolates were respectively: TRB: 0.025 mg/L, PSC: 0.032 mg/L, ITC: 0.050 mg/L and VRC: 0.059 mg/L with lower values and CAS: 0.31 mg/L, KTZ: 0.56 mg/L and GRZ: 0.76 mg/L with higher values.

CONCLUSION

Diverse ITS sequence types of T. benhamiae were shown in different geographical regions of Iran. The TRB, PSC and ITC were the most effective drugs against T. benhamiae strains, respectively. Furthermore, in our study, two strains of T. eriotrephon as a scarce dermatophyte species were described.

In-Vitro Activity of Nano Fluconazole and Conventional Fluconazole against Clinically Important Dermatophytes

Background:

Dermatophytosis is one of the most common fungal infections in humans. Antifungals such as fluconazole are effectively used for treating dermatophytosis; however, drug resistance was observed in many cases. Therefore, a newer treatment strategy is essential.

Methods:

This study (Conducted in the Laboratory of the School of Public Health, Tehran University of Medical Sciences, Tehran, Iran in 2018) evaluated the antifungal susceptibility of nano fluconazole compared to conventional fluconazole on dermatophyte isolates using CLSI M38-A2guidelines. Dermatophyte species isolated from clinical cases of dermatophytosis were identified using PCR sequencing techniques. Zeta potential and size of the nano particles containing fluconazole were measured; scanning electron microscope (SEM) was used to determine nano particle structure.

Results:

The size of liposomal fluconazole obtained was 88.9 ± 12.14 nm with –20.12 ± 3.8 mV for zeta potential. The encapsulation rate for fluconazole was 75.1± 4.2%. MIC₅₀ for the three tested species was 32, 16, and 8 μg/ml for Trichophyton interdigitale, T. rubrum, and Epidermophyton floccosum isolates, respectively. The corresponding values for nano fluconazole were 8 μg/ml for the three tested species.

Conclusion:

MIC value for nano-fluconazole was lower than conventional fluconazole in all dermatophytes species tested; therefore, nano-fluconazole could inhibit the growth of dermatophytes better than fluconazole at a lower concentration of the drug.

Molecular epidemiology and in vitro antifungal susceptibility of Trichophyton schoenleinii, agent of tinea capitis favosa

Trichophyton schoenleinii is an anthropophilic dermatophyte usually causing tinea favosa. Only few studies have provided data on molecular epidemiology and antifungal profiles of this fungus due to its limited prevalence after 1950s. Forty-nine strains from Asia (n = 27), Africa (n = 10), Europe (n = 10) and from unknown regions (n = 2) were analysed with amplified fragment length polymorphism fingerprinting (AFLP) to reveal intraspecific genetic diversity in this dataset. Amplified fragment length polymorphism fingerprinting genotyping revealed five clusters which did not correspond to geographic origins or clinical characteristics. Additionally, in vitro antifungal susceptibility to seven antifungals was provided for all strains. Terbinafine, ketoconazole, miconazole and itraconazole proved to be the most effective drugs, followed by griseofulvin. No correlation between genotypes and differences in antifungal susceptibility was observed. It is concluded that the AFLP groups are lineages within a single species.

Revival of favus in Japan caused by Trichophyton schoenleinii

Favus is a type of dermatophytosis known to produce yellow scutula around hair follicles. Most cases of this disease worldwide are infections of Trichophyton schoenleinii. Favus has rarely been reported in Japan throughout the last four decades, and T. schoenleinii has not been clinically isolated in any case during the period. Here, we report a case of favus of vellus hair observed in a 63-year-old Japanese woman. Fungal culture showed negative; however, we detected fungal elements in the crust and hair bulbs by Grocott staining. Pathogenic fungi were identified as T. schoenleinii by polymerase chain reaction-based DNA sequencing, targeting the internal transcribed spacer regions of the rRNA gene using the formalin-fixed, paraffin-embedded tissue sample. She was successfully treated with p.o. administration of terbinafine and topical application of luliconazole cream.

Dermatophyte Resistance to Antifungal Drugs: Mechanisms and Prospectus

Dermatophytes comprise pathogenic fungi that have a high affinity for the keratinized structures present in nails, skin, and hair, causing superficial infections known as dermatophytosis. A reasonable number of antifungal drugs currently exist on the pharmaceutical market to control mycoses; however, their cellular targets are restricted, and fungi may exhibit tolerance or resistance to these agents. For example, the stress caused by antifungal and cytotoxic drugs in sub-inhibitory concentrations promotes compensatory stress responses, with the over-expression of genes involved in cellular detoxification, drug efflux, and signaling pathways being among the various mechanisms that may contribute to drug tolerance. In addition, the ATP-binding cassette transporters in dermatophytes that are responsible for cellular efflux can act synergistically, allowing one to compensate for the absence of the other, revealing the complexity of drug tolerance phenomena. Moreover, mutations in genes coding for target enzymes could lead to substitutions in amino acids involved in the binding of antifungal agents, hindering their performance and leading to treatment failure. The relevance of each one of these mechanisms of resistance to fungal survival is hard to define, mainly because they can act simultaneously in the cell. However, an understanding of the molecular mechanisms involved in the resistance/tolerance processes, the identification of new antifungal targets, as well as the prospective of new antifungal compounds among natural or synthetic products, are expected to bring advances and new insights that facilitate the improvement or development of novel strategies for antifungal therapy.