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We compared the minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs) of azoles in antifungal drug-susceptible, terbinafine-resistant, and lowly itraconazole (ITCZ)-susceptible strains of dermatophytes. To assess the MICs of ITCZ, ravuconazole (RVCZ), efinaconazole (EFCZ), and luliconazole (LUCZ) in the isolates, broth microdilution assays were performed based on the Clinical and Laboratory Standards Institute M38-A2 guidelines with modifications. After the assays for determining the MICs, the inoculum suspensions in wells were resuspended, then 10 μL of the growth solution in each well was inoculated onto potato dextrose agar with the use of a pipette. After 7 days of incubation at 28°C, the MFCs were determined as the lowest concentration of a drug that allowed the growth of colonies on the potato dextrose agar. The MICs in the dermatophytes were <0.03 to >32 mg/L for ITCZ, <0.03 to 4 mg/L for RVCZ, <0.03 to 2 mg/L for EFCZ, and <0.03 mg/L for LUCZ. The MFCs in the dermatophytes were 1 to >32 mg/L for ITCZ, 0.06 to >32 mg/L for RVCZ, <0.03 to 4 mg/L for EFCZ, and <0.03 to 2 mg/L for LUCZ. If the drug susceptibility test shows that the fungi are resistant to the drug, the treatment can be changed to a susceptible drug in advance, or if the fungi are low-susceptible, the treatment can be done with the recognition that it may require a longer treatment period than usual., (© 2024 Japanese Dermatological Association.)

An epidemiological study of antifungal drug-resistant dermatophytes was conducted as a follow-up to our 2020 survey. Dermatophytes were isolated in 2022 from the same dermatology clinics as in the previous study. In total, 288 Trichophyton interdigitale and Trichophyton rubrum clinical isolates were obtained from 288 human cases of dermatophytosis in Tokyo, Saitama, Shizuoka, and Kumamoto, Japan. Four strains were found to be resistant to terbinafine (TRF) and susceptible to itraconazole (ITZ), luliconazole (LCZ), and ravuconazole (RVZ), and three other strains were found to be resistant to ITZ and susceptible to TRF, LCZ, and RVZ. We determined the sequences of the squalene epoxidase (SQLE)-encoding gene in the three TRF-resistant T. rubrum strains, and found that two strains harbored L393F missense mutations, and one strain harbored a F397L missense mutation. The results of the present study indicated that the prevalence of TRF-resistant dermatophytes has not increased since 2020. However, TRF-resistant T. interdigitale (L393F mutation) was isolated for the first time, indicating that attention should be paid to the presence of TRF-resistant T. interdigitale in the future. We also examined for the first time the epidemiology of ITZ-resistant T. rubrum in Japanese patients. Although the number of ITZ-resistant strains was not large, the results confirmed that ITZ-resistant T. rubrum strains do exist in Japanese patients., (© 2023 Japanese Dermatological Association.)

We encountered two cases of phaeohyphomycosis caused by Exophiala jeanselmei and E. oligosperma that were treated with fosravuconazole and terbinafine, respectively. Our cases were successfully treated with empiric therapy before the pathogen's species or antifungal sensitivity had been determined. We summarized 32 cases of cutaneous and subcutaneous phaeohyphomycosis caused by Exophiala species in Japan. The patients received antifungals, including itraconazole, terbinafine, voriconazole, and fosravuconazole, and the treatment success rates of these monotherapies were 77% (17/22), 67% (8/12), 100% (5/5), and 50% (1/2), respectively. Although the broad-spectrum azole antifungal itraconazole is the first choice for treatment, terbinafine at 125 mg/day might exert the same efficacy. Fosravuconazole is a novel broad-spectrum azole and a moderate inhibitor of Cyp3A4 that causes fewer drug interactions than itraconazole and voriconazole, indicating a promising drug for this disease., (© 2022 Japanese Dermatological Association.)

Terbinafine (TRF) has been used in the treatment of fungal infections for more than 20 years. Recently, TRF-resistant Trichophyton interdigitale and T. rubrum strains have been isolated from human patients worldwide. However, an epidemiological study of TRF-resistant strains in Japanese patients has not been investigated. In the present study, antifungal susceptibility testing was performed on clinical isolates from Japanese patients to assess TRF-resistance patterns of T. interdigitale and T. rubrum strains. We also sequenced the squalene epoxidase (SQLE) encoding gene of TRF-resistant T. rubrum strains. Two hundred and ten T. interdigitale and T. rubrum clinical isolates were obtained from 210 human cases of tinea pedis, tinea corporis, tinea unguium, tinea cruris, tinea manuum, tinea faciei and tinea capitis in Tokyo, Saitama, Chiba, Hyogo and Kumamoto, Japan, in 2020. Five T. rubrum isolates (N74, N79, N99, H30 and K2) grew on Sabouraud's dextrose agar (SDA) containing 1 mg/L of TRF. All five strains exhibited TRF minimum inhibitory concentrations (MICs) ≥32 mg/L but remained susceptible to azoles. We determined SQLE sequences in these TRF-resistant T. rubrum strains and found that all strains harbored missense mutations (L393F) in the SQLE-encoding gene., (© 2021 Japanese Dermatological Association.)

Fosravuconazole is a novel oral antifungal drug developed in Japan and used to treat tinea unguium since 2018. Its excellent oral absorbability and systemic bioavailability has enabled short-duration therapy of 3 months. Furthermore, no concomitant drugs are contraindicated due to the presence of the mild inhibitor of cytochrome P450 enzyme which is responsible for polypharmacy adverse effects. Therefore, it can be safely administrated to elderly patients. Elderly patients (≥65 years old) with severe onychomycosis (≥50% nail involvement) were treated with oral fosravuconazole 100 mg once daily for 12 weeks. The rate of involvement improved from 86.6% to 28.1% (P < 0.01). The efficacy (i.e. percentage of those rated as "improved" and better) and cure rate was 83.8% (31/37) and 29.7% (11/37), respectively. Furthermore, when focusing on the thin nail group (<3 mm), the efficacy and cure rate was 88.2% (15/17) and 58.8% (10/17), respectively. Although the serum γ-glutamyltransferase levels increased in 21.6% (8/37), all patients recovered without any specific treatments., (© 2020 Japanese Dermatological Association.)

A 73-year-old healthy woman noticed black pigmentation on both thumbnails for 6 years. Upon her visit to our clinic, she had pigmented onychomycosis with onycholysis in the distal area. There was no evidence of paronychia. Direct microscopy using Zoomblue™ and histopathological examination showed aggregated blastoconidia. Fontana-Masson staining confirmed fungal melanin production. A combination of morphological features and genetic testing identified the isolates as Candida parapsilosis. Fungal melanonychia due to C. parapsilosis is rare, with only six cases reported since 1979. The minimum inhibitory concentration of the isolates was 0.25 μg/mL for itraconazole, less than 0.03 μg/mL for ravuconazole and 2.0 μg/mL for terbinafine. Both oral terbinafine treatment and itraconazole pulse therapy performed for 6 months were unsuccessful. The disease was ultimately cured with a 3-month treatment of oral fosravuconazole., (© 2019 Japanese Dermatological Association.)

Trichophyton interdigitale is an anthropophilic species that is frequently isolated from tinea unguium and tinea pedis throughout the world. In the present study, antifungal susceptibility testing was performed on T. interdigitale isolates from Japanese patients (isolated in 2017-2018; 24 strains) to assess itraconazole (ITZ) and terbinafine (TRF) susceptibility of these strains. E-test determinations revealed that the mean ITZ minimum inhibitory concentration (MIC) of the 24 strains was 0.023 mg/L (range, 0.064-1). Clinical Laboratory Standards Institute M38-A2 determinations revealed that the mean TRF MIC of 23 of the 24 strains was less than 0.03125 mg/L. Among these strains, one (NUBS18016) had a TRF MIC of 2 mg/L, confirming its resistance to TRF. The predicted amino acid sequences of the squalene epoxidase (SQLE) gene from the TRF-resistant strain (NUBS18016) was 100% identical to the SQLE gene sequence of the reference strain T. interdigitale, indicating that no gene mutations were present in NUBS18016. Therefore, the TRF-resistance mechanism of our TRF-resistant strain NUBS18016 has not been defined. Dermatologists should be cautious about the prevalence of foot dermatophytosis due to antifungal drug-resistant strains., (© 2019 Japanese Dermatological Association.)

The patient was a 73-year-old healthy female farmer who had been treated with terbinafine for 25.5 months by a primary physician. She exhibited a discoloration and thickening of the right big toenail. She had no concomitant paronychia. Direct microscopy revealed chlamydoconidia and hyphae, and periodic acid-Schiff stained nail specimen showed septate hyphae. On the basis of these morphological features and gene analysis, the final diagnosis was ungual hyalohyphomycosis caused by Fusarium proliferatum. Topical application of 10% efinaconazole solution cured the disease in 10 months., (© 2016 Japanese Dermatological Association.)

Trichophyton mentagrophytes were isolated from 19 of 20 guinea pigs in a children’s corner of a zoo. The nucleotide sequence identity of the internal transcribed spacer region among 19 guinea pig isolates was 99%, including the reference strain of animal type 3 of T. mentagrophytes. The genomic DNA of all isolates were investigated for the mating (MAT) gene by specific polymerase chain reaction. The alpha-box gene was detected in all 19 isolates, while the high-mobility-group (HMG) gene was detected in only one of 19 isolates. Therefore, the guinea pig population harbored at least 2 MAT types of Arthroderma vanbreuseghemii. The T. mentagrophytes that was prevalent in this population may constitute a constant source of infection for persons coming into contact with guinea pigs.

Sporotix schenckii is a pathogenic fungus that causes human and animal sporotrichosis, and based on morphology of the sessile conidia and molecular analysis, it was recently recognized as a species complex comprising at least the following six sibling species: S. albicans, S. brasiliensis, S. globosa, S. luriei, S. mexicana and S. schenckii. However, apart from S. schenckii sensu strict, only S. brasiliensis, S. globosa and S. luriei are associated with human and animal infection. S. globosa has been most commonly isolated in Asia, Europe and the USA; therefore, molecular epidemiological study for S. globosa is important in relation to human sporotrichosis in Japan. To the best of our knowledge, this is the first study to determine the mating type 1-2 (MAT1-2) gene of Sporothrix schenckii with the aim of understanding the taxonomy of the genus Sporothrix. The MAT1-2 gene (1618 bp) encodes a protein sequence of 198 amino acids. Reverse transcription polymerase chain reaction analysis also detected MAT1-2 gene mRNA expression in all of the S. schenckii strains examined, indicating that this gene is expressed in S. schenckii cells. Phylogenetic analysis of the MAT1-2 gene fragments of Ophiostoma himal-ulmi, O. novo-ulmi, O. ulmi and S. schenckii indicated that these isolates could be classified into four clusters. MAT1-1 gene-specific polymerase chain reaction was positive in 15 isolates, but negative in four human isolates and one feline isolate., (© 2013 Japanese Dermatological Association.)

The recent description (in GenBank) of a urease-encoding gene from Trichophyton rubrum provides an opportunity to compare this species to the highly similar T. rubrum var. raubitschekii. Therefore, the corresponding genomic DNA was recovered from T. rubrum var. raubitschekii, and the sequence and expression were compared for this urease gene in urease-positive and -negative isolates of T. rubrum and T. rubrum var. raubitschekii. The sequence (2371 bp) of the T. rubrum var. raubitschekii urease gene revealed the presence of three exons. Except for a three-amino acid insertion, the predicted proteins were identical, but demonstrated protein identity of approximately 70% compared to an Arthroderma gypseum homolog. Reverse transcription polymerase chain reaction analysis revealed the presence of a corresponding transcript in both urease-positive T. rubrum var. raubitschekii isolates examined; the same analysis did not detect this transcript in urease-negative isolates of T. rubrum., (© 2012 Japanese Dermatological Association.)

Trichophyton rubrum var. raubitschekii is a rare anthropophilic dermatophyte isolated around the world from tinea corporis, tinea cruris, tinea pedis and tinea unguium. In this study, the isolation rate of T. rubrum var. raubitschekii was studied in 200 cases of tinea pedis and tinea unguium in Japan. The 200 clinical isolates were shown to be of downy type as their colonies on Sabouraud's dextrose agar were white to cream, suede-like to downy, with a yellow-brown to wine-red reverse, and they produced few macroconidia. The type strain of T. rubrum var. raubitschekii (CBS 100084) and one clinical isolate (KMU 8337; isolated at Kanazawa) of downy type tested positive for urease, but the reference strain of T. rubrum (CBS 392.58) and the remaining 199 clinical isolates tested negative. Further epidemiological investigations are required to study human cases of infection with the granular type of T. rubrum and T. rubrum var. raubitschekii in Japan., (© 2012 Japanese Dermatological Association.)

Black dot ringworm (BDR), caused by Trichophyton violaceum var. glabrum (T. glabrum), was observed in a 28-year-old Japanese female who had been treated with prednisolone (22.5 mg/day) for systemic lupus erythematosus. It was successfully treated with oral terbinafine (125 mg/day) for 12 weeks. The causative fungus was identified by molecular analysis as well as morphological and biochemical examination. The chitin synthase 1 (CHS1) gene cleavage pattern of the clinical isolate with restricted enzyme HinfI was identical to that of T. violaceum. We reviewed previous reports of BDR to determine the historical trend of this infection in Japan. Since 1974, 93 Japanese cases have been reported. The age distribution was bi-modal: the higher peak consisted of children (aged 0-15 years), and the lower peak was composed of the elderly (aged 60-75 years). In the elderly group, females were predominant (M:F=1:22, p<0.001). T. violaceum, including T. glabrum, was identified as the most common causative fungus of BDR (75.3%). Sixty percent of cases showed slight erythema. In 8 families, 16 cases were found to be intrafamilial infections. A history of previous steroid treatment was described in about 40%.