Program and Abstracts of Annual Meeting of the Japanese Society for Medical Mycology

Malassezia yeasts are cutaneous microflora commonly found in animals and human and sometimes cause various opportunistic skin diseases. As most of Malassezia species are lipid-dependent, lipolytic enzymes are necessary for them to obtain lipids from the environment and then lipase and phospholipase which degrade neutral lipids and phospholipids, respectively, are thought to play an important role for growth and pathogenicity of Malassezia. Here we investigated a common culture condition for several Malassezia spp. and these secretory lipase and phospholipase activities comparably. Interestingly, lipase and phospholipase activities in M. globosa strains revealed the highest values in the lipid-dependent Malassezia spp.. M. globosa also showed higher activities of these lipolytic enzymes than M. pachydermatis known to possess high phospholipase activity. From these results, it was supposed that secretory lipase and phospholipase activities relate to the dominant survival of M. globosa found in many patients.

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Glycosylceramide (GlcCer) is present in almost all of eukaryotic organisms. Its ceramide backbone usually carries some functional groups such as hydroxy group, double bond, and methyl branch at aliphatic carbon atoms. Many yeast species such as Candida albicans possess a fungal-specific GlcCer which consists of long chain fatty acid and (4E, 8E)-9-methylsphinga-4, 8-dienine as ceramide. On the other hand, a budding yeast Saccharomyces cerevisiae, which has been studied by a lot of basic researcher, is not capable of synthesizing GlcCer, so that the functional and physiological roles of this sphingolipid in many fungi has been little known. To investigate the necessity of fungal-specific GlcCer for growth and cell differentiation of C. albicans, we have identified a functional sphingolipid Δ8-desaturase gene (SLD) and constructed sld disruptant in this yeast. From the analysis of sld disruptant, this disruption caused to decrease in the elongation of hypha during the induction of hyphal growth. This result suggested that introduction a double bond at the Δ8 position of sphingoidbase included in GlcCer has indirectly some relationship with the morphological change of C. albicans.

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Our group has reported the unique cell cycle pattern of Cryptococcus neoformans, different from that of the model budding yeast Saccharomyces cerevisiae. To clarify the cell cycle mechanisms, homologues of cell cycle control genes in C. neoformans were cloned. We have previously reported the cloning of the CDC28/Cdc2 homologue, CnCdk1 and three Cdk1 cyclin homologues: two B-type G2/M cyclins and a single G1 cyclin, CnCln1. Further search of the C. neoformans genome database however did not yield additional ORFs with G1 cyclin similarities. Sequence analysis and comparison with other cyclin sequences showed that CnCln1 possesses the typical amino acid residues conserved among G1 cyclins. Complementation test in a triple G1 cyclin mutant showed that CnCln1 can perform G1 functions in S. cerevisiae. We also attempted and succeeded, in obtaining a deletion mutant of CnCln1 by biolistic transformation. G1 cyclin deletion in C. neoformans resulted to abnormally enlarged cells, delayed growth and subsequent hyphal formation, indicating a role for CnCln1 in morphogenesis; but apparently is not essential, pointing out to the existence of bypass mechanisms to replace its functions.

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We report a case of kerion celsi caused by Trichophyton(T.) tonsurans in a 14-year-old student of one middle school wrestling team. The lesion was manifested by 6.5 x 5.0 x 1.0 cm sized, markedly inflammatory, swollen, boggy plaque exuding pus on the scalp for 1 month. Culture from a scalp lesion of patient on Sabouraud dextrose agar showed T. tonsurans.
The patient was treated with 250mg of terbinafine daily for 12 weeks and short term therapy of low dose of prednisolone. Skin lesions were completely cured and recurrence is not observed to date.

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