Aspergillus sections Flavi, Nigri, and Terrei are known as common causative agents of aspergillosis, followed by section Fumigati. A previous study investigated the distribution of section Fumigati in Izu and Ogasawara Islands and found that the dominant species changes depending on the soil environment. This study investigated the species diversity and distribution of sections Flavi, Nigri, and Terrei in Mukojima, Hahajima, and Chichijima of Ogasawara Islands and clarified whether the dominant species vary depending on the soil environment, as in section Fumigati. The strains were isolated from soil samples collected in 2019 and 2020 at 18 sites in three islands, including different landscapes, and species identification was based on the nucleotide sequence of the calmodulin gene. Overall, 172 strains were isolated from all sites and identified to seven section Flavi, five section Nigri, and three section Terrei species. Three section Flavi, three section Nigri, and one section Terrei species have been reported as causative agents of aspergillosis. Three sections were distributed in Chichijima and Hahajima, but only section Nigri was found in Mukojima. The frequency of occurrence of Aspergillus tamarii and Aspergillus nomiae belonging to section Flavi and Aspergillus niger and Aspergillus tubingensis belonging to section Nigri were > 60% in forests, including shrub forests, whereas that of Aspergillus floccosus belonging to section Terrei was > 40% in bare land and grassland. Aspergillus pseudonomiae belonging to section Flavi was isolated at > 40% frequency of occurrence regardless of the landscape. Thus, differences of soil environments affected the distribution of the dominant species belonging to three sections.

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Phaeohyphomycosis is a rare subcutaneous fungal infection caused by melanin-containing brown-pigmented fungi. It typically occurs after skin injury in immunocompromised individuals. Herein, we report a case of phaeohyphomycosis caused by Exophiala xenobiotica in an immunocompromised elderly Japanese female. A subcutaneous mass on her left lower leg was totally removed but reappeared two months later. The subcutaneous mass resolved with additional seven months of 200 mg/day of oral itraconazole treatment. E. xenobiotica was identified as a new black yeast species in 2006. Genetic identification of the species was useful for identify the etiologic agent and choice of antifungal drugs.

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An epidemiological study of terbinafine (TBF)-resistant dermatophytes was conducted in 2023 as a follow-up to our 2020 and 2022 surveys. Dermatophytes were isolated in 2023 from the same dermatology clinics in Tokyo, Saitama, Shizuoka, and Kumamoto, Japan, as in the previous studies. In total, 311 isolates (122 Trichophyton interdigitale isolates, 1 Trichophyton indotineae isolate, and 188 Trichophyton rubrum isolates) were obtained from 311 human cases of dermatophytosis (195 tinea pedis cases, 54 tinea unguium cases, 28 tinea corporis cases, 27 tinea cruris cases, and 7 tinea manuum cases). Ten strains (1 T. interdigitale strain and 9 T. rubrum strains) were found to be resistant to TBF, and susceptible to efinaconazole, itraconazole, luliconazole, and ravuconazole. The isolation rate of TBF-resistant strains was 2.3% in 2020, 1.4% in 2022, and 3.2% in 2023. We determined the sequences of the squalene epoxidase-encoding gene in 10 TBF-resistant strains, and found that all strains harbored missense and/or deletion mutations. These results indicate that the prevalence of TBF-resistant dermatophytes has increased when compared to the previous studies.

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Terbinafine (TBF)-resistant anthropophilic dermatophytes have recently been isolated from human patients around the world. Almost all TBF-resistant strains of dermatophytes have the amino acid substitution in the squalene epoxidase (SQLE) gene. In this study, we performed whole genome sequencing of a TBF-resistant Microsporum canis strain (designated 47C) to clarify the mechanisms underlying TBF- resistance conferred by genetic mutations. Strain 47C, isolated from a cat with feline dermatophytosis in China in 2018, was previously identified as the first TBF-resistant M. canis. Approximately 2.5 µg of genomic DNA sample was extracted from growing mycelium of 47C and sequenced using a PacBio Sequel IIe system. We mapped the 23.2 Mb genome against the reference M. canis CBS 113480 strain (assembly ASM15114v1 in GenBank) and identified 1,455 genetic variations, including substitutions, insertions and deletions (INDELs). Our analysis initially focused on whether mutations existed in the SQLE gene, which is known to encode SQLE. We discovered a T→C mutation at 1183 bp (F395L mutation) in the putative SQLE gene of strain 47C. In contrast, seven TBF-susceptible strains exhibited no mutations in their SQLE genes. The F395L mutation likely reduces the affinity of TBF for SQLE in M. canis, similar to the F397L mutation found in TBF-resistant Trichophyton rubrum and Trichophyton interdigitale.

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Background: Candida auris is an emerging fungus causing nosocomial infections and outbreaks, with many strains exhibiting multidrug resistance. This study analyzed the C. auris clinical isolates at The Jikei University School of Medicine Kashiwa Hospital from December 2019 to March 2021.
Methods: Clinical data were reviewed retrospectively for patients from whom C. auris was isolated from clinical specimens. Clade analysis and drug susceptibility testing were conducted.
Results: Three strains of C. auris were isolated, all from otorrhea in patients with otitis externa. Case A was a 69-year-old female with aural pain, Case B was an 82-year-old female with left ear deafness, and Case C was a 76-year-old male with left otorrhea and hearing loss; all cases were immunocompetent. Strains from Clade I (South Asian clade) were found in Cases A and C, and a strain from Clade II (East Asian clade) was isolated from Case B. None had a travel history overseas or contact with foreigners. Drug susceptibility testing showed that one C. auris strain of Clade Ⅰ had a high minimal inhibitory concentration for fluconazole. No severe infection was observed, and all cases improved with local treatment, including ketoconazole ointment for Case A.
Conclusion: The presence of Clade I C. auris strains in Japan without travel history raises concerns about domestic or in-hospital transmission. Accurate identification and rigorous infection control are essential to manage the spread of C. auris. Ongoing surveillance, research, and international cooperation are needed.

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Approximately one million new cases of cryptococcosis develop each year worldwide, resulting in approximately 600,000 deaths. Most cases occurred in HIV patients from African countries south of the Sahara Desert. In light of this situation, in 2022, the World Health Organization presented a list of priority fungal pathogens to guide research, development, and public health action, with Cryptococcus neoformans as the most important critical fungus. In contrast, a recent retrospective study in developed countries showed that 90% of cases with cryptococcosis were non-HIV patients, including immunocompetent individuals. Underlying diseases of non-HIV immunocompromised patients include cancer and solid organ transplantation. High serum titers cryptococcal antigens independently predicted the risk of central nervous system involvement. Even if the patient is asymptomatic, high antigen levels are considered a possibility of cryptococcal meningitis, and a spinal fluid examination may be recommended. The absence of a history of contact with pigeons should not be used as a basis for denying cryptococcosis because C. neoformans is often detected in old and dried feces of chickens other than pigeons. Donor-derived cryptococcosis is a unique feature of cryptococcosis in solid organ transplant recipients. Pre-transplant screening tests for cryptococcosis, pre-transplant treatment for the donor, and prophylactic antifungal therapy for the recipient may be useful. Defense against cryptococcal infection is regulated by various mechanisms, including Th1, Th2, and Th17 immune responses. Molecularly targeted medicines that target specific cytokines or surface antigen molecules have been widely used with excellent clinical efficacy for the treatment of various diseases. Since cryptococcosis has been recently reported to develop during the use of certain medicines, such as ibrutinib and eculizumab, clinicians need to be mindful that the number of similar cases may increase in the future.

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