The multi-antifungal drug-resistant strain (NUBS21012) of Trichophyton rubrum was isolated from a patient with recurrent tinea corporis. The resistant strain encoded Phe at codon 393 instead of Leu ...(L393F) in the squalene epoxidase (
) gene. The expression of genes encoding ATP-binding cassette transporter proteins increased in the strain compared to that of other strains. This result provides evidence that ATP-binding cassette transporter proteins are closely associated with azole resistance.
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.
Terbinafine (TRF)-resistant Trichophyton interdigitale and Trichophyton rubrum have been isolated from human patients. These strains have missense mutations (Leu393Ser/Phe or Phe397Leu) in the ...squalene epoxidase-encoding gene, SQLE. We developed a PCR detection method to identify hotspot mutation sites in SQLE genes of dermatophytes. To sequence hotspots in isolates, we prepared primers based on conserved sequences of T. rubrum and T. interdigitale SQLEs. Approximately 390-bp long DNA bands for T. rubrum, T. interdigitale, and Trichophyton indotineae strains were sequenced. Hotspots were detected only in TRF-resistant strains. This PCR-based method is simpler and more rapid than the conventional test.
Cutaneous cryptococcosis is classified either as primary or secondary based on the route of infection. The disease can also be classified either as localized cutaneous cryptococcosis or cutaneous ...manifestations of disseminated cryptococcosis. However, from a physician's point of view, whether lesions are localized to the skin or are disseminated/systemic is more important than the route of infection. The Clinical Practice Guidelines for Diagnosis and Treatment of Cryptococcosis, which was established in 2019 by the Japanese Society for Medical Mycology, adopted the latter classification. Localized cutaneous cryptococcosis is defined as a condition in which lesions are confined within a limited part of the skin, not systemically disseminated at the same time, and are associated with neither cryptococcal fungemia nor antigenemia. This type of cutaneous cryptococcosis is uncommon in Japan. Only 65 cases were reported during the 50-year study period from 1968 to August 2018, with the patients divided into two groups: immunocompromised patients (n=44, 68%) and immunocompetent patients (n=21, 32%). None of the patients were infected with the human immunodeficiency virus (HIV). Localized cutaneous cryptococcosis can also occur in non-HIV-infected patients and well-appearing individuals, therefore, it is considered an important infection in routine dermatology practice. Here, we outline the classification, diagnosis, and treatment of cutaneous cryptococcosis and present a summary of cutaneous cryptococcosis cases reported in Japan.
The Dermatophyte Test Strip visualizes mycotic antigens by immunochromatography. It allows easy and fast detection of dermatophytes. A multicenter, single‐arm, comparative clinical study was designed ...to evaluate the capacity of Dermatophyte Test Strip to detect dermatophytes in suspected tinea unguium specimens in comparison with direct microscopy and polymerase chain reaction (PCR). Signed consent was obtained from 222 subjects and all subjects completed the study. With the Dermatophyte Test Strip, dermatophytes were detected in 201 of 222 (90.5%) specimens but not in 21 of 222 (9.5%) specimens. With direct microscopy, dermatophytes were detected in 170 of 222 (76.6%) specimens but not in 52 of 222 (23.4%). Of the 45 specimens that showed inconsistent results between the two methods, PCR gave further results for 40 specimens, of which 37 (92.5%) specimens were positive and three (7.5%) were negative for dermatophytes. The positive concordance rate, negative concordance rate and overall concordance rate between the Dermatophyte Test Strip and direct microscopy were 81.1%, 66.7% and 79.7%, respectively. When inconsistent results were corrected using the results of PCR, these rates were 97.5%, 71.4% and 95.0%, respectively. When five specimens that could not be tested by PCR because no piece for the PCR test was left were excluded from analysis, these rates were 99.0%, 78.9% and 97.2%, respectively. The present results indicate good detection capacity of the Dermatophyte Test Strip. The Dermatophyte Test Strip provides a reliable, convenient and quick method to test for tinea unguium.
In this review, we summarize the status of Trichophyton tonsurans infection in Japan in terms of epidemiology, clinical features, diagnosis and infection control. Since approximately 2000, outbreaks ...of T. tonsurans infections among combat sports club members have been reported frequently, with the infection then spreading to their friends and family members. The most common clinical features of T. tonsurans infection are tinea corporis, which is difficult to differentiate from eczema, and tinea capitis. Tinea capitis is classified as the seborrheic form, kerion celsi form or “black dot” form, although 90% or more of patients are asymptomatic carriers. The diagnosis of symptomatic T. tonsurans infection is established by potassium hydroxide examination and fungal culture. However, because there are many asymptomatic carriers of T. tonsurans infection, tests using the hairbrush culture method are necessary. An increase in asymptomatic carriers of T. tonsurans makes assessment of the current prevalence of the infection challenging and underscores the importance of educational efforts and public awareness campaigns to prevent T. tonsurans epidemics.
Ravuconazole (RVCZ) is a new human anti-fungal azole drug available in Japan since 2018 and is a broad-spectrum agent that exhibits excellent activity against dermatophytes. In the present study, the ...in vitro RVCZ susceptibility of clinical isolates of anthropophilic dermatophytes, including Trichophyton interdigitale strains with either low susceptibility to itraconazole (ITCZ) or resistance to terbinafine (TEBR), was investigated using the Clinical & Laboratory Standards Institute M38-A2 test. The MICs of RCVZ for 20 clinical isolates of T. interdigitale were < 0.03125–0.125 mg/L; for 4 clinical isolates of T. rubrum, < 0.03125–0.0625 mg/L; and for 20 clinical isolates of T. tonsurans, < 0.03125 mg/L. Similarly, the MICs of RCVZ for the T. interdigitale strains with either low susceptibility to ITCZ or resistance to TEBR were also < 0.03125 mg/L. To our knowledge, this is first study to investigate the in vitro RVCZ susceptibility of T. interdigitale strains with either low susceptibility to ITCZ or resistance to TEBR. Our results indicated that RVCZ was the most effective drug against these strains.
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.
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.
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