Dandruff and seborrheic dermatitis are common afflictions of the human scalp caused by commensal scalp fungi belonging to the genus Malassezia. Malassezia globosa and Malassezia restricta are the predominant species found on the scalp. The intergenic spacer regions of these species' rRNA genes contain short sequence repeats (SSR): (GT)n and (CT)n in M. globosa and (CT)n and (AT)n in M. restricta. In the present study, we compared the genotypes (SSR) of M. globosa and M. restricta colonizing the scalps of patients with dandruff and healthy individuals. For M. globosa, the genotype (GT)10:(CT)8 (40.3 %, 25/62) was predominant followed by (GT)9:(CT)8 (14.5 %, 9/62) and (GT)11:(CT)8 (14.5 %, 9/62) in patients with dandruff, whereas the genotypes in healthy subjects were diverse. For M. restricta, the genotype (CT)6:(AT)6 (59.7 %, 37/62) was predominant followed by (CT)6:(AT)8 (24.2 %, 15/62) in patients with dandruff, while four genotypes, (CT)6:(AT)6 (10.5 %, 6/57), (CT)6:(AT)7 (22.8 %, 13/57), (CT)6:(AT)8 (17.5 %, 10/57), and (CT)6:(AT)10 (21.1 %, 12/57), accounted for 71.9 % of all combinations in healthy subjects. The results of this study suggest that the M. globosa genotype (GT)10:(CT)8 and the M. restricta genotype (CT)6:(AT)6 may be involved in the development of dandruff.

Background: Trichosporon asahii is the major causative agent of disseminated and deep-seated trichosporonosis. It is capable of forming biofilms on surfaces, leading to medical device-related infection. Trichosporon asahii may be present as yeast form, hyphae and/or arthroconidia; however, the relationship between its biofilm-forming ability and its morphological transition is unclear. Objectives: We investigated whether the T. asahii morphological transition contributes to its biofilm formation. We also determined the conditions required to induce each of the morphologies. Methods: Three high-and three low-biofilm-producing strains (HBS and LBS, respectively) were selected using a biofilm formation assay, and the cell surface hydrophobicity of these six strains was measured. For each strain, the morphology was observed and the number of each morphological form (yeast form, hypha and arthroconidium) was counted to calculate the ratio. Finally, the ability of cells each morphological type to adhere to the polystyrene substrate was evaluated. Results: The HBS exhibited abundant arthroconidia and hyphae; in contrast, the LBS produced mainly hyphae with few or no arthroconidia. The production of hyphae was increased by nitrogen-containing medium, and the production of arthroconidia was increased by nitrogen-deficient medium. Cells incubated under nitrogen-deficient conditions showed higher adherence to a polystyrene surface than those incubated in the presence of nitrogen. Conclusion: Arthroconidia of T. asahii play a key role in biofilm formation by promoting cellular adhesion.

Bloodstream infection by the pathogenic fungus Candida albicans is a major health problem. Candidemia is often associated with medical devices, which can act as substrates for biofilm development. Biofilm-related infections are relatively difficult to treat because of their resistance to antimicrobial agents. It is therefore important to explore the mechanisms of biofilm formation. Dimorphism is a major contributor to biofilm formation in C. albicans. To determine whether the hypha-related proteins Pra1 (pH-regulated antigen) and Zrt1 (zinc transporter) are responsible for biofilm formation, the ability of pra1 and zrt1 deletion mutants to form biofilms was investigated. Biofilm formation by both deletion mutants was less than that of the wild-type strain. Because Pra1 and Zrt1 are also related to the zinc homeostasis system, the effects of adding zinc on biofilm formation were also examined. Biofilm formation was increased in the presence of zinc. These data suggest that Pra1 and Zrt1 regulate biofilm formation through zinc homeostasis.

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Here, we report the draft genome sequence of Trichosporon domesticum JCM 9580, isolated from the house of a patient with summer-type hypersensitivity pneumonitis (SHP) in Japan. This genomic information will help elucidate the mechanisms of the development of SHP.

Candida albicans is a pathogenic fungus that causes deep mycosis in immunocompromised patients and forms a biofilm on catheter surfaces. Here we showed that C. albicans infection of silkworms led to biofilm formation on the surface of polyurethane fibers, a catheter substrate material, while inside the silkworm body. Silkworms inserted with polyurethane fibers survived for at least 48 hours. When silkworms inserted with polyurethane fibers were subsequently infected with C. albicans, biofilm formed on the surface of the polyurethane fiber within 24 hours in the silkworm body. These results suggest that silkworms can be used to evaluate C. albicans biofilm formation.

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Biofilms are formed by microorganisms and their products on the surface of materials such as medical devices. Biofilm formation protects microorganisms from antimicrobial agents. Bacteria and fungi often form dual-species biofilms on the surfaces of medical devices in clinical settings. An experimental system to evaluate in vivo biofilm formation by the pathogenic fungus Candida albicans was established using silkworms inserted with polyurethane fiber (PF), a catheter material. In the present study, we established an in vivo experimental system using silkworms to evaluate the antimicrobial tolerance of Escherichia coli in single- and dual-species biofilms formed on the surface of the PF. The injection of E. coli into the PF-inserted silkworms led to the formation of a biofilm by E. coli on the surface of the PF. E. coli in the biofilm exhibited tolerance to meropenem (MEPM). Furthermore, when E. coli and C. albicans were co-inoculated into the PF-inserted silkworms, a dual-species biofilm formed on the surface of the PF. E. coli in the dual-species biofilm with C. albicans was more tolerant to MEPM than E. coli in the single-species biofilm. These findings suggest the usefulness of an in vivo experimental system using PF-inserted silkworms to investigate the mechanisms of MEPM tolerance in E. coli in single- and dual-species biofilms.