Therapy and Antifungal Susceptibility Profile of Microsporum canis

Phytotherapeutic potential of Artemisia ludoviciana and Cordia boissieri extracts against the dermatophyte Microsporum canis

Introduction

Microsporum canis is a dermatophyte that mainly affects dogs and cats. However, it can be transmitted to humans by direct contact. This makes it one of the most frequent causative agents of dermatophytosis in humans, reflecting the frequent human close relationships with pets. Conventional treatment relies on antifungal pharmacological agents. However, errors in application have led to the occurrence of fungal resistance and toxic effects. Consequently, new therapeutic alternatives are needed for M. canis infections. Plant extracts have been explored as phytotherapeutics for the treatment of dermatophyte infections, which prompted an attempt to apply extracts of the ethnopharmacologically important plants Artemisia ludoviciana and Cordia boissieri.

Material and Methods

Methanolic extracts of these two plants were obtained using a Soxhlet method and were characterised by phytochemical screening. Extracts were evaluated against a M. canis commercial strain (ATCC-11621) using the microdilution method described in the Clinical and Laboratory Standards Institute protocol M38-A, determining its minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC). Subsequently, these concentrations were tested in a human keratinocyte human cell line.

Results

Artemisia ludoviciana and C. boissieri extracts showed MIC values of 2,500 and 1,250 µg/mL, and MFC values of 5,000 and 2,500 µg/mL against M. canis, respectively. These extracts did not inhibit HaCaT cell proliferation in vitro.

Conclusion

The evaluated extracts showed potential for the treatment of M. canis fungal infections. However, further studies on their phytochemical characterisation, purification, clinical safety and formulation are required.

Tinea capitis caused by Microsporum canis: A case study of three family members in India, a non-endemic region

INTRODUCTION

Tinea capitis, a common scalp infection primarily affecting children, is caused by keratinophilic dermatophytic fungi, notably Microsporum and Trichophyton species. Microsporum canis, primarily transmitted from cats and dogs to humans, is rarely reported in non-endemic regions like India. We report a cases involving three family members from Delhi, India, diagnosed with tinea capitis caused by Microsporum canis. The index case, a five-year-old boy, contracted the infection through contact with a cat, while his younger brother and sister acquired it through human-to-human transmission within the family.

METHODS

Clinical examination, microscopic analysis, and molecular identification techniques confirmed the diagnosis. Antifungal susceptibility testing revealed sensitivity to itraconazole and terbinafine but resistance to griseofulvin.

RESULTS

Treatment with oral terbinafine and topical ketoconazole cream led to successful outcomes for all three patients. Molecular typing confirmed clonality of the isolates, indicating human-to-human transmission.

CONCLUSION

This case study underscores the significance of considering atypical sources of infection and human-to-human transmission in the diagnosis and management of tinea capitis caused by Microsporum canis in non-endemic regions. It emphasizes the necessity of thorough contact history assessment and appropriate antifungal therapy for effective control of the infection.

Modeling, the Optimization of the Composition of Emulgels with Ciclopirox Olamine, and Quality Assessment

The design and development of pharmaceutical products require specific knowledge, time, and investment. Response surface methodology (RSM) is a widely used technique in the design of experiments (DoE) to optimize various processes and products. The aim of this study was to model and produce experimental emulgels containing 1% ciclopirox olamine and to evaluate their physical, rheological, and mechanical properties and their ability to release ciclopirox olamine. The objective was to optimize the composition of the experimental emulgel containing 1% ciclopirox olamine by applying a central composite design based on selected criteria. The surfactant (polysorbate 80) had the greatest influence on the physical, rheological, and mechanical properties of the emulgels, as well as on the release of ciclopirox olamine from these systems. During the optimization process, an emulgel of optimal composition was generated containing 38.27% mineral oil, 6.56% polysorbate 80, and 55.17% hydrogel containing 1% ciclopirox olamine, meeting specified criteria (dependent variables) including the maximum flux of ciclopirox olamine, the minimum sol-gel transition temperature (Tsol/gel), and the minimum particle size of the oil phase. The oil phase particle size (D50) of this emulgel was determined to be 0.337 µm, the system Tsol/gel was 9.1 °C, and the flux of ciclopirox olamine from this gel matrix was calculated to be 1.44 mg/cm2. This emulgel of optimal composition could be used to treat fungal skin diseases.

Epidemiologic features and therapeutic strategies of kerion: A nationwide multicentre study

BACKGROUND

Kerion is a severe type of tinea capitis that is difficult to treat and remains a public health problem.

OBJECTIVES

To evaluate the epidemiologic features and efficacy of different treatment schemes from real-world experience.

METHODS

From 2019 to 2021, 316 patients diagnosed with kerion at 32 tertiary Chinese hospitals were enrolled. We analysed the data of each patient, including clinical characteristics, causative pathogens, treatments and outcomes.

RESULTS

Preschool children were predominantly affected and were more likely to have zoophilic infection. The most common pathogen in China was Microsporum canis. Atopic dermatitis (AD), animal contact, endothrix infection and geophilic pathogens were linked with kerion occurrence. In terms of treatment, itraconazole was the most applied antifungal agent and reduced the time to mycological cure. A total of 22.5% of patients received systemic glucocorticoids simultaneously, which reduced the time to complete symptom relief. Furthermore, glucocorticoids combined with itraconazole had better treatment efficacy, with a higher rate and shorter time to achieving mycological cure.

CONCLUSIONS

Kerion often affects preschoolers and leads to serious sequelae, with AD, animal contact, and endothrix infection as potential risk factors. Glucocorticoids, especially those combined with itraconazole, had better treatment efficacy.

Antifungal activity of Carica papaya fruit extract against Microsporum canis: in vitro and in vivo study

Background

Tinea capitis (T. capitis), commonly known as scalp ringworm, is a fungal infection affecting the scalp and hair. Among the causative agents, Microsporum canis (M. canis) stands out, often transmitted from cats to humans (zoonotic disease). In this study, we investigated the efficacy of Carica papaya (C. papaya), fruit extract against dermatophytes, particularly M. canis, both in vitro and in vivo. Additionally, we aimed to identify the active compounds responsible for suppressing fungal growth and assess the toxicity of C. papaya on human cells.

Methodology

It conducted in two parts. First, In Vitro Study include the preparation of C. papaya fruit extract using methanol as the solvent, Phytochemical analysis of the plant extract including Gas chromatography-mass spectrometry (GC-MS) and Fourier-transform infrared spectroscopy (FTIR) was conducted, Cytotoxicity assays were performed using HUH-7 cells, employing the MTT assay (1-(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide), Antimicrobial activity against M. canis was evaluated, including: Zone of inhibition (ZI), Minimum inhibitory concentration (MIC), Minimum fungicidal concentration (MFC), M. canis cell alterations were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Second, In Vivo, Albino Wistar male rats were included.

Results

The phytochemical analysis of the methanolic extract from papaya revealed several functional groups, including hydroxyl, ammonia, alkane, carbonate, and alcohol. Additionally, the GC-MS analysis identified 15 compounds, with xanthosine and decanoic acid being the predominant components. The methanolic extract of papaya fruits demonstrated potent antifungal activity: ZI = 37 mm, MIC = 1,000 μg/mL, MFC = 1900 μg/mL, MTT results indicated lower cytotoxicity of the fruit extract at concentrations of 20 μg/mL, 50 μg/mL, 100 μg/mL, 150 μg/mL, and 200 μg/mL, The IC50 revealed a significant decrease in cell viability with increasing extract concentration. Notably, papaya extract induced considerable alterations in the morphology of M. canis hyphae and spores. In animal tissue, improvements were observed among the group of rats which treated with Papaya extract. This study highlights the potential of C. papaya fruits as a natural antifungal agent, warranting further exploration for clinical applications.

The inhibitory effects of zinc oxide nanoparticles on clinical isolates of Microsporum canis in dogs and cats

INTRODUCTION

Microsporum canis is the most common dermatophyte infecting pets and their owners, and its long duration of treatment and increasing rate of drug resistance have caused the attention of researchers to be directed towards the use of nanoparticles and new alternatives for treatment. This study investigated the antifungal effects of zinc oxide (ZnO) nanoparticles on clinical isolates of M. canis in dogs and cats and subtilisin 1 (SUB1) gene expression.

MATERIALS AND METHODS

Zinc oxide nanoparticles were prepared using the wet chemical method at a concentration of 4000 ppm. Its antifungal potential was evaluated at concentrations of 62.5-4000 ppm by disk diffusion and microdilution methods against 10 isolates of M. canis. The effect of this product on SUB1 gene expression was investigated by quantitative real-time PCR method.

RESULTS

The results of the disk diffusion test showed that the highest inhibitory diameter was at the highest concentration of ZnO nanoparticles (34 mm), and the inhibitory zone was observed in dilutions up to 250 ppm. The minimum inhibitory concentration (MIC) of ZnO nanoparticles was between 250 and 500 ppm, and the minimum fungicidal concentration was between 500 and 1000 ppm. There was a significant reduction in SUB1 gene expression in sub-MIC concentration (125-250 ppm) (p < 0.05).

CONCLUSION

This study showed that ZnO nanoparticles have a concentration-dependent inhibitory effect on M. canis. Moreover, ZnO nanoparticles could decrease the expression of SUB1, an enzyme involved in fungi adhesion to the epidermis. Nevertheless, more studies must be done in the future to determine the possible side effects and safety of ZnO nanoparticles along with their efficacy in vivo.

Microsporum gypseum Infection Among Two Related Families With a Zoonotic Aspect: A Prospective Case Series

Background and purpose The Microsporum gypseum complex is a globally distributed group of geophilic dermatophytes that primarily affect animals but can also rarely cause dermatomycoses in humans. With some regional and occupational variations, tinea corporis is the most prevalent presentation of the infection. The aim of this study was to report on the diagnosis and treatment of dermatophytosis cases among related families, and their pets, from southern Saudi Arabia. Up-to-date information on dermatophytes and dermatophytosis is needed. Methods This is a prospective case series undertaken at the Dermatology Outpatient Clinic of King Khalid University, Saudi Arabia. Six patients with suspected dermatophytosis were received at our hospital in 2022 and have been followed for recovery with or without scars. Characteristics of fungal pathogens were examined phenotypically on the basis of microscopic and growth characteristics, and laboratory data were used to initiate treatment with oral fluconazole, topical terbinafine cream, or oral itraconazole. Results Clinical features and culture results confirmed tinea capitis and tinea corporis caused by M. gypseum, which was also present in a pet cat. Tinea capitis cases (n = 4) did not respond to fluconazole and terbinafine treatment, but treatment with itraconazole resulted in a full recovery. Tinea corporis cases (n = 2) were treated with terbinafine, which resulted in a full recovery within four weeks, with no signs of scarring. Conclusions M. gypseum presents with serious persistent lesions and is extremely contagious. Treatment is durable but challenging, and breaking the transmission chain is more difficult.

Antibacterial and Antimycotic Activity of Epilobium angustifolium L. Extracts: A Review

The aim of this work was to provide an overview of available information on the antibacterial and antifungal properties of Epilobium angustifolium extracts. A literature search of Scopus, PubMed/Medline, and Google Scholar for peer-reviewed articles published between January 2000 and June 2023 was undertaken. A total of 23 studies were eligible for inclusion in this review. Significant variation of antimicrobial activity depending on the tested species and strains, type of extract solvent, or plant organs utilized for the extract preparation was found. E. angustifolium extracts were active against both Gram-positive and Gram-negative bacteria and showed antimycotic effects against the fungi of Microsporum canis and Trichophyton tonsurans and the dermatophytes Arthroderma spp. Greater susceptibility of Gram-positive than Gram-negative bacteria to fireweed extracts was found. A strong antibacterial effect was recorded for Staphylococcus aureus, Bacillus cereus, Micrococcus luteus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii including multi-drug resistant strains. E. angustifolium extract might find practical application as an antimicrobial in wound healing, components of cosmetic products for human and animals, or as food preservatives.

A Comprehensive Insight into Māmaki (Pipturus albidus): Its Ethnomedicinal Heritage, Human Health Research, and Phytochemical Properties

In Hawaii, the plants P. albidus, P. forbesii, P. kauaiensis, and P. ruber are collectively known as māmaki in ethnomedicine, where P. albidus predominates. Farmed māmaki is becoming increasingly popular in Hawaii and the United States. Māmaki teas (such as bottled Shaka tea) are the dominant product. Historically, māmaki has been utilized for its medicinal properties, promoting well-being and good health through consuming tea made from its leaves, ingesting its fruit, and incorporating it into ointments. Māmaki holds cultural significance among Native Hawaiians and is widely used in ethnic medicine, having been incorporated into traditional practices for centuries. However, the scientific mechanisms behind its effects remain unclear. This review consolidates current knowledge of māmaki, shedding light on its potential therapeutic properties, physical properties, nutritional and mineral composition, and active phytochemicals. We also highlight recent research advances in māmaki's antibacterial, anti-viral, chemopreventive, anti-inflammatory, and antioxidant activities. Additionally, we discuss future prospects in this field.

Effects of Coleus amboinicus L. Essential Oil and Ethanolic Extracts on Planktonic Cells and Biofilm Formation of Microsporum canis Isolated from Feline Dermatophytosis

Microsporum canis is an important zoonotic fungus that causes dermatophytosis in domestic animals and their owners. Domestic cats are the primary reservoir for M. canis. Antifungal drugs frequently produce adverse effects on the host animal, increasing the demand for novel alternative treatments derived from nature. We evaluated the antifungal activity of Coleus amboinicus essential oil (CEO) and ethanolic extracts (CEE) against M. canis in planktonic and biofilm growth. Twelve clinical isolates of M. canis were identified in feline dermatophyte samples. Using GC-MS, 18 compounds were identified in CEO, with carvacrol being the major constituent. HPLC analysis of CEE revealed that it contained rosmarinic acid, apigenin, and caffeic acid. The planktonic growth of all M. canis isolates was inhibited by C. amboinicus extracts. The minimum inhibitory concentration at which ≥50% of the isolates were inhibited (MIC₅₀) was 128 µg/mL (32-256 µg/mL) for both CEO and CEE. The MIC₉₀ values of CEO and CEE were 128 and 256 µg/mL, respectively. CEO at MIC (128 µg/mL) and 2× MIC (256 µg/mL) significantly inhibited the biofilm formation of weak, moderate, and strong biofilm-producing M. canis. CEE at 2× MIC (256 µg/mL) significantly inhibited the biofilm formation of all isolates. Overall, C. amboinicus extracts inhibited planktonic growth and exhibited a significant antibiofilm effect against M. canis. Thus, C. amboinicus is a potential source of natural antifungal compounds.

Immunomodulatory responses of differentially polarized macrophages to fungal infections

Macrophages, the first line of defense against invasive fungi in the innate immune system, are widely distributed in the blood and tissues of the body. In response to various internal and external stimulators, macrophages can polarize into classically activated macrophages (M1) and alternatively activated macrophages (M2). These two types of polarized macrophages play different roles in antifungal activity and in maintaining the steady-state balance between inflammation and tissue repair. However, the antifungal mechanisms of M1- and M2-type macrophages have not been fully described. In this review, the immune regulatory mechanisms against pathogenic fungi of these two classical types of macrophages in various tissues are summarized. The effects of antifungal factors on macrophage differentiation are also highlighted. The description of these data, on the one hand provides valuable insight for future investigations and also highlights new strategies for the treatment of pathogenic fungal infections.

Important Mycoses of Wildlife: Emphasis on Etiology, Epidemiology, Diagnosis, and Pathology—A Review: PART 1

Simple Summary

The number of wild animals is steadily declining globally, so the early diagnosis and proper treatment of emerging diseases are vital. Fungal diseases are commonly encountered in practice and have a high zoonotic potential. This article describes aspergillosis, candidiasis, histoplasmosis, cryptococcosis, and penicilliosis, and is only the first part of a detailed review. The laboratory methods (fungal isolation, gross pathology, histopathology, histochemistry, cytology, immunohistochemistry, radiography, CT, PCR, or ELISA) used in the diagnosis and the clinical details that provide a complete view of the mycoses are presented.

Abstract

In the past few years, there has been a spurred tripling in the figures of fungal diseases leading to one of the most alarming rates of extinction ever reported in wild species. Some of these fungal diseases are capable of virulent infections and are now considered emerging diseases due to the extremely high number of cases diagnosed with fungal infections in the last few decades. Most of these mycotic diseases in wildlife are zoonotic, and with the emergence and re-emergence of viral and bacterial zoonotic diseases originating from wildlife, which are causing devastating effects on the human population, it is important to pay attention to these wildlife-borne mycotic diseases with zoonotic capabilities. Several diagnostic techniques such as fungal isolation, gross pathology, histopathology, histochemistry, cytology, immunohistochemistry, radiography, CT, and molecular methods such as PCR or ELISA have been invaluable in the diagnosis of wildlife mycoses. The most important data used in the diagnosis of these wildlife mycoses with a zoonotic potential have been re-emphasized. This will have implications for forestalling future epidemics of these potential zoonotic mycotic diseases originating from wildlife. In conclusion, this review will highlight the etiology, epidemiology, diagnosis, pathogenesis, pathogenicity, pathology, and hematological/serum biochemical findings of five important mycoses found in wild animals.

Clinically used antifungal azoles as ligands for gold(III) complexes: the influence of the Au(III) ion on the antimicrobial activity of the complex

In a search for novel antimicrobial metal-based therapeutic agents, mononuclear gold(III) complexes 1-7 of the general formula [AuCl₃(azole)], where azole stands for imidazole (im, 1), 1-isopropylimidazole (ipim, 2), 1-phenylimidazole (phim, 3), clotrimazole (ctz, 4), econazole (ecz, 5), tioconazole (tcz, 6) and voriconazole (vcz, 7) were synthesized, characterized and biologically evaluated. In all complexes, the corresponding azole ligand is monodentately coordinated to the Au(III) via the imidazole or triazole nitrogen atom, while the remaining coordination sites are occupied by chloride anions leading to the square-planar arrangement. In vitro antimicrobial assays showed that the complexation of inactive azoles, imidazole, 1-isopropylimidazole and 1-phenylimidazole, to the Au(III) ion led to complexes 1-3, respectively, with moderate activity against the investigated strains and low cytotoxicity on the human normal lung fibroblast cell line (MRC-5). Moreover, gold(III) complexes 4-7 with clinically used antifungal agents clotrimazole, econazole, tioconazole and voriconazole, respectively, have, in most cases, enhanced antimicrobial effectiveness relative to the corresponding azoles, with the best improvement achieved after complexation of tioconazole (6) and voriconazole (7). The complexes 4-7 and the corresponding antifungal azoles inhibited the growth of dermatophyte Microsporum canis at 50 and 25 μg mL^-1. Gold(III) complexes 1-3 significantly reduced the amount of ergosterol in the cell membrane of Candida albicans at the subinhibitory concentration of 0.5 × MIC (minimal inhibitory concentration), while the corresponding imidazole ligands did not significantly affect the ergosterol content, indicating that the mechanism of action of the gold(III)-azole complexes is associated with inhibition of ergosterol biosynthesis. Finally, complexes 5 and 6 significantly reduced the production of pyocyanin, a virulence factor in Pseudomonas aeruginosa controlled by quorum sensing, and increased cell survival after exposure to this bacterium. These findings could be of importance for the development of novel gold(III)-based antivirulence therapeutic agents that attenuate virulence without pronounced effect on the growth of the pathogens, offering a lower risk for resistance development.

Phylogeny, Antifungal Susceptibility, and Point Mutations of SQLE Gene in Major Pathogenic Dermatophytes Isolated From Clinical Dermatophytosis

Drug resistance is one of the major challenges to skin fungal infections, especially in tropical and subtropical infections caused by dermatophytes. This study aimed to determine the antifungal susceptibility of clinically dermatophytes and evaluate point mutations in terbinafine-resistant isolates. A total number of 123 clinical dermatophyte isolates in eight species were evaluated in terms of sensitivity to seven major antifungals. Furthermore, the point mutation in squalene epoxidase (SQLE) gene responsible for terbinafine resistance was studied. The dermatophytes species were identified by morphological characteristics and confirmed by the ITS sequencing. Also, the phylogenetic tree was drawn using the RAxML analyses for 123 dermatophytes isolates. A new XXIX genotype was also found in 4 Trichophyton mentagrophytes isolates. Based on the results obtained, terbinafine was the most effective antifungal drug followed by itraconazole and voriconazole. Trichophyton rubrum and Trichophyton tonsurans were the most susceptible species (MIC₅₀ = 0.01, 0.09 μg/ml), and T. mentagrophytes was the most resistant species (MIC₅₀ = 0.125 μg/ml) to terbinafine. Of the 123 dermatophytes isolates, six isolates showed reduced susceptibility to terbinafine, and only Trichophyton indotineae had a mutation in SQLE gene as a Phe397Leu substitution. Overall, the antifungal susceptibility test is necessary for managing dermatophytosis. These results help physicians to control the course of the disease and provide further insights to select effective drugs for patients with dermatophytosis, especially in tropical and subtropical regions of the world, where dermatophytosis is still a public health problem.

Subtyping Options for Microsporum canis Using Microsatellites and MLST: A Case Study from Southern Italy

Microsporum canis is considered one of the most common zoophilic dermatophyte species causing infections in animals and humans worldwide. However, molecular epidemiological studies on this dermatophyte are still rare. In this study, we aimed to analyse the population structure and relationships between M. canis strains (n = 66) collected in southern Italy and those isolated from symptomatic and asymptomatic animals (cats, dogs and rabbits) and humans. For subtyping purposes, using multilocus sequence typing (MLST) and multilocus microsatellite typing (MLMT), we first used a limited set of strains to screen for variability. No intraspecies variability was detected in six out of the eight reference genes tested and only the ITS and IGS regions showed two and three sequence genotypes, respectively, resulting in five MLST genotypes. All of eight genes were, however, useful for discrimination among M. canis, M. audouinii and M. ferrugineum. In total, eighteen microsatellite genotypes (A-R) were recognized using MLMT based on six loci, allowing a subdivision of strains into two clusters based on the Bayesian iterative algorithm. Six MLMT genotypes were from multiple host species, while 12 genotypes were found only in one host. There were no statistically significant differences between clusters in terms of host spectrum and the presence or absence of lesions. Our results confirmed that the MLST approach is not useful for detailed subtyping and examining the population structure of M. canis, while microsatellite analysis is a powerful tool for conducting surveillance studies and gaining insight into the epidemiology of infections due to this pathogen.

Transcriptome sequencing revealed the inhibitory mechanism of ketoconazole on clinical Microsporum canis

Background

Microsporum canis is a zoonotic disease that can cause dermatophytosis in animals and humans.

Objectives

In clinical practice, ketoconazole (KTZ) and other imidazole drugs are commonly used to treat M. canis infection, but its molecular mechanism is not completely understood. The antifungal mechanism of KTZ needs to be studied in detail.

Methods

In this study, one strain of fungi was isolated from a canine suffering with clinical dermatosis and confirmed as M. canis by morphological observation and sequencing analysis. The clinically isolated M. canis was treated with KTZ and transcriptome sequencing was performed to identify differentially expressed genes in M. canis exposed to KTZ compared with those unexposed thereto.

Results

At half-inhibitory concentration (½MIC), compared with the control group, 453 genes were significantly up-regulated and 326 genes were significantly down-regulated (p < 0.05). Quantitative reverse transcription polymerase chain reaction analysis verified the transcriptome results of RNA sequencing. Gene ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that the 3 pathways of RNA polymerase, steroid biosynthesis, and ribosome biogenesis in eukaryotes are closely related to the antifungal mechanism of KTZ.

Conclusions

The results indicated that KTZ may change cell membrane permeability, destroy the cell wall, and inhibit mitosis and transcriptional regulation through CYP51, SQL, ERG6, ATM, ABCB1, SC, KER33, RPA1, and RNP genes in the 3 pathways. This study provides a new theoretical basis for the effective control of M. canis infection and the effect of KTZ on fungi.

2-Hydroxychalcone as a Potent Compound and Photosensitizer Against Dermatophyte Biofilms

Dermatophytes, fungi that cause dermatophytosis, can invade keratinized tissues in humans and animals. The biofilm-forming ability of these fungi was described recently, and it may be correlated with the long treatment period and common recurrences of this mycosis. In this study, we evaluated the anti-dermatophytic and anti-biofilm activity of 2-hydroxychalcone (2-chalcone) in the dark and photodynamic therapy (PDT)-mediated and to determine its mechanism of action. Trichophyton rubrum and Trichophyton mentagrophytes strains were used in the study. The antifungal susceptibility test of planktonic cells, early-stage biofilms, and mature biofilms were performed using colorimetric methods. Topographies were visualized by scanning electron microscopy (SEM). Human skin keratinocyte (HaCat) monolayers were also used in the cytotoxicity assays. The mechanisms of action of 2-chalcone in the dark and under photoexcitation were investigated using confocal microscopy and the quantification of ergosterol, reactive oxygen species (ROS), and death induction by apoptosis/necrosis. All strains, in the planktonic form, were inhibited after treatment with 2-chalcone (minimum inhibitory concentration (MIC) = 7.8-15.6 mg/L), terbinafine (TRB) (MIC = 0.008–0.03 mg/L), and fluconazole (FLZ) (1–512 mg/L). Early-stage biofilm and mature biofilms were inhibited by 2-chalcone at concentrations of 15.6 mg/L and 31.2 mg/L in all tested strains. However, mature biofilms were resistant to all the antifungal drugs tested. When planktonic cells and biofilms (early-stage and mature) were treated with 2-chalcone-mediated PDT, the inhibitory concentrations were reduced by four times (2–7.8 mg/L). SEM images of biofilms treated with 2-chalcone showed cell wall collapse, resulting from a probable extravasation of cytoplasmic content. The toxicity of 2-chalcone in HaCat cells showed higher IC₅₀ values in the dark than under photoexcitation. Further, 2-chalcone targets ergosterol in the cell and promotes the generation of ROS, resulting in cell death by apoptosis and necrosis. Overall, 2-chalcone-mediated PDT is a promising and safe drug candidate against dermatophytes, particularly in anti-biofilm treatment.

Virulence and Antifungal Susceptibility of Microsporum canis Strains from Animals and Humans

The enzymatic and antifungal profiles of dermatophytes play an important role in causing infections in humans and animals. This study aimed to assess the virulence factors produced by Microsporum canis strains, in vitro antifungal profile and the relationship between virulence, antifungal profile and occurrence of lesions in animals and humans. A total of 100 M. canis strains from humans with tinea corporis (n = 10) and from animals presenting (n = 64) or not (n = 26) skin lesions was employed to evaluate phospholipase (Pz), hemolytic (Hz), lipase (Lz), catalase (Ca), and thermotolerance (GI) activities. In addition, in vitro antifungal profile was conducted using the CLSI broth microdilution method. A statistically significant difference (p < 0.05) in Lz and Ca values was revealed among strains from hosts with and without lesions. Voriconazole, terbinafine, and posaconazole were the most active drugs followed by ketoconazole, griseofulvin, itraconazole, and fluconazole in decreasing activity order. The significant positive correlation between azole susceptibility profile of M. canis and virulence factors (i.e., hemolysin and catalase) suggest that both enzyme patterns and antifungal susceptibility play a role in the appearance of skin lesions in animals and humans.

Antifungal susceptibility testing of dermatophytes: Development and evaluation of an optimised broth microdilution method

BACKGROUND

Dermatophytosis is one of the most common infections affecting 3%-17% of the population. Resistance to antifungals so far was not of concern in the therapeutic management. However, recent reports of terbinafine-resistant strains in several countries are worrisome making antifungal susceptibility testing inevitable.

OBJECTIVES

We aimed to develop and evaluate an optimised broth microdilution assay for antifungal drug susceptibility testing of dermatophytes.

METHODS

We first studied the effect of different inocula, incubation temperatures and incubation times to establish an optimised assay. Subsequently, we tested 79 clinical strains of 11 dermatophyte species with 13 antifungals.

RESULTS

We found inoculating with 0.5-5 × 10⁴ colony forming units (CFU) and incubating at 29°C ± 1°C for 4 days to be appropriate. Terbinafine was the most active antifungal agent with minimum inhibitory concentration (MIC) values ≤ 0.06 µg/mL, expect for one resistant T mentagrophytes strain, which was isolated from an Indian patient. Also, a majority of MICs of other antifungals that are commonly used to treat dermatophytosis were low, except those of fluconazole. Fluconazole MICs do not correlate with the good efficacy in the clinical management.

CONCLUSIONS

Our assay enables fast and reliable susceptibility testing of dermatophytes with a large panel of different antifungals. This helps to improve the therapeutic management of dermatophytosis by detecting resistant strains.

Comparative evaluation of E-test and CLSI methods for Itraconazole, Fluconazole and Ketoconazole susceptibilities of Microsporum canis strains

The incidence of resistance to antifungal agents for dermatophytes is increasing, but most of the methods currently available to test the antifungal susceptibility of Microsporum canis still require standardization. The aims of this study were: (i) to evaluate the antifungal susceptibility of M. canis strains recovered from animals to ketoconazole (KTZ), fluconazole (FLZ) and itraconazole (ITZ) using a modified CLSI broth microdilution (CLSI M38-A2-BMD) and the E-test® protocols and (ii) to estimate the agreement between the methods. Tentative azole epidemiological cutoff values (ECVs) were also proposed in order to interpret the results of in vitro susceptibility tests and to establish the agreement between the E-test and CLSI BMD methods. A total of forty clinical M. canis strains from animals with skin lesions were tested, and the essential (EA) and categorical agreement (CA) between the two methods were determined. KTZ displayed the lowest MIC values, while ITZ and FLZ the highest. The ECV for KTZ and ITZ were 4 μg/ml, while those of FLZ was 64 μg/ml. Based on ECVs, about 88% of M. canis strains were susceptible to all azoles being a cross-resistance with ITZ-FLZ registered for one strain. A total of five M. canis strains showed MIC > ECV for FLZ using CLSI, while one strain showed MIC > ECV for ITZ using both tests. KTZ, ITZ and FLZ showed EA ranging from 92.5 to 95%, for all azoles and CA > 97% except for FLZ (87.5%). The good CA between the E-test and the CLSI BMD provides evidence of the reliability of the former method to test the antifungal susceptibility of M. canis for ITZ and KTZ and not for FLZ.

The best type of inoculum for testing the antifungal drug susceptibility of Microsporum canis: In vivo and in vitro results

BACKGROUND

Data correlating in vitro drug susceptibility of Microsporum canis with clinical outcomes of its infections are lacking as well as the most suitable inoculum and incubation time in broth microdilution assays.

OBJECTIVES AND METHODS

Microsporum canis strains were collected from animal hosts that tested positive (Group I; n = 13) and negative (Group II; n = 14) to this pathogen following itraconazole (ITC) therapy. In vitro ITC susceptibility was assessed according to the Clinical Laboratory Standards Institute (CLSI M38-A2) methodology using conidia, hypha-conidia and arthroconidia at 3 and 7 days of incubation in order to assess the most suitable inoculum and incubation time. Successively, ketoconazole (KTC), voriconazole (VRC), terbinafine (TRB), posaconazole (PSZ), fluconazole (FLC) and griseofulvin (GRI) susceptibilities were assessed using the chosen inoculum.

RESULTS

The MIC values of ITC after three-day incubation were equal than those recorded after 7-day incubation. Itraconazole MICs were ≤1 μg/mL for strains from Group II and >1 μg/mL for those of Group II only when conidia were used. All strains showed high susceptibility to VRC, POS, TEB and low susceptibility to ITC, KTC, GRI and FLC regardless of the source and incubation time.

CONCLUSIONS AND CLINICAL IMPORTANCE

Results suggest that correlation between the in vitro results and clinical outcome was observed only by incubating conidia for 3 days at 30 ± 2°C. These conditions might be most suitable to assess in vitro susceptibility of M. canis and assist in determining the occurrence of drug resistance and cross-resistance phenomena.

Synergistic Effects of Efflux Pump Modulators on the Azole Antifungal Susceptibility of Microsporum canis

The microbiologic and clinical resistance of dermatophytes is seldom reported, and the mechanisms associated with resistance are not well known. This study investigated the effect of efflux pump modulators (EPMs) (i.e., haloperidol HAL and promethazine PTZ) and their inhibiting activity on the minimum inhibitory concentrations of itraconazole (ITZ) and fluconazole (FLZ) against selected M. canis strains. M. canis strains with low (≤ 1 μg/ml itraconazole and < 64 μg/ml fluconazole) and high (> 1 μg/ml itraconazole and ≥ 64 μg/ml fluconazole) azole MIC values were tested using Checkerboard microdilution assay. The disk diffusion assay, the minimum fungicidal concentration and the time-kill assay were also performed in order to confirm the results of checkerboard microdilution assay. The MIC values of ITZ and FLZ of M. canis decreased in the presence of subinhibitory concentrations of HAL and PTZ, the latter being more effective with a greater increased susceptibility. Synergism was observed in all strains with high azole MICs (FICI < 0.5) and no synergism in the strains with low azole MICs. A fungicidal activity was observed after 48 h of incubation when ITZ and FLZ were tested in combination with HAL or PTZ. These results suggest that the drug efflux pumps are involved in the defense mechanisms to azole drugs in M. canis strains. The synergism might be related to an increased expression of efflux pump genes, eventually resulting in azole resistance phenomena. Complementary studies on M. canis resistance are advocated in order to investigate the molecular mechanisms of this phenomenon.

In vitro activities of 15 antifungal drugs against a large collection of clinical isolates of Microsporum canis

BACKGROUND

Microsporum canis is a zoophilic species, found to be the most frequently isolated species in animals. M. canis causes sporadic outbreaks of infections in humans, such as the one that occurred in Canada, where more than 1000 human cases were detected over an 8-year period. Despite the medical importance of M. canis infections, there are limited in vitro data on the antifungal susceptibility to antifungal drugs, including new generation triazoles and imidazoles.

OBJECTIVE

The aim of the current study was to comprehensively evaluate the in vitro activity of new azoles and comparator drugs against a large panel of M. canis isolates using a microdilution assay.

METHODS

The in vitro susceptibility to novel triazoles and imidazoles was compared to that of other antifungal drugs using a large collection of M. canis clinical isolates (n = 208) obtained from patients and animals with dermatophytosis in Iran, France and Turkey.

RESULTS

All isolates exhibited high susceptibility to the majority of the tested antifungal agents. However, luliconazole, lanoconazole and efinaconazole, as well as econazole, demonstrated superior activity against all strains in comparis on with the other drugs.

CONCLUSION

FDA-approved antifungal drugs, that is luliconazole, efinaconazole and lanoconazole, showed the highest antifungal activity and should be promising candidates for the treatment of dermatophytosis caused by M canis. However, their therapeutic effectiveness remains to be determined in clinical settings.