Cell walls (0.1-0.5μm in thickness) of dermatophytes, at least Trichophyton mentagrophytes and Epidermophyton floccosum, are built of microfibrils (20nm in diameter) and matrix embedding the fibrils. These fibrils are composed of chitin (70-80%) and a small amount of glucans, and the matrix is composed of β-1-3, β1-6 glucan, glucomannan, galactomannan and peptides. Another characteristic structure is the outermost layer (20-50nm in thickness) of the cell wall, which consists of hydrophobic protein rodlets.
Lipids are thought to play important roles in the regulation of dimorphism and virulence in pathogenic fungus. Generally, the ratio of phospholipid/ergosterol is less than 1 in yeast form and 2-20 in mycelial form cells in Candida albicans and Sporothrix schenckii. During the transition from yeast to mycelial forms, phosphatidylinositol and phosphatidylserine are reduced, whereas phosphatidylcholine increases. Phospholipase D is activated on this transition. Phospholipase B is now known to be a virulence factor in C. albicans.
Polyene antifungal agents bind to ergosterol in membrane to form complexes, which generate pores and destroy the structures and functions of membrane. Azole antifungal agents inhibit the synthesis of ergosterol leading to deficiency in ergosterol content in membrane, and impair the function of membranes in fungal cells. We show the effects of polyenes on the ultrastructure of fungal plasma membrane and impairment of ionomycin-induced calcium influx in T. mentagrophytes, so that we can compare the differences in mode of actions between these two groups of agents.

View full abstract

Over the past two decades the incidence of deep mycoses caused by several major groups of fungal pathogens such as Candida spp., aspergilli, Cryptococcus neoformans and zygomycetes has risen steadily. Moreover, opportunistic fungal infections due to Fusarium spp., Trichosporon spp., Pseudallescheria boydii and other emerging pathogens, as well as fluconazole-resistant Candida albicans, all of which are often resistant to existing antifungal drugs, are also encountered more and more frequently. This makes it more difficult for the clinician to achieve successful treatment. Thus there is an urgent need to develop new antifungal agents or formulations with advantages over and/or complimentary to existing drugs. This review focuses on current approaches to antifungal chemotherapy with special reference to the clinical development of new drugs, including (ii) lipid formulations of amphotericin B, (i) second-generation azoles and (iii) antifungal lipopeptides.

View full abstract

Though the concept of semi-invasive pulmonary aspergillosis was advocated in 1981 by Gefter et al., its histopathological appearence has not yet been reported in detail. Pathological studies on fungus ball type pulmonary aspergillosis (PA) were originally made mainly in regard to related bronchi. Chronic-progressive destructive changes cannot be completely explained from this viewpoint alone. Clinically, since bloody sputum and hemoptysis appeared frequently, further studies on the pulmonary vasculature were considered necessary.
In the resected lungs of 3 cases of semi-invasive pulmonary aspergillosis, the pathological features of pulmonary vasculature were characterized by numerous fungal clots within pulmonary arteries and veins, marked destruction of pulmonary blood vessels and extensive intravascular fibrin deposition. Intravascular fibrin deposition causes stasis of blood flow, promotes intravascular proliferation of aspergilli and probably accelerates pulmonary destruction caused by blood stasis. Important pathological findings of fungus ball type pulmonary aspergillosis of the semi-invasive subtype with clinical aspects of chronic-progressive lung destruction caused by severe inflammation, were reported for both the vascular and the bronchial system.

View full abstract

Deep-seated trichosporonosis is a lethal opportunistic infection in immunocompromised patients. For the rapid diagnosis of this condition, we developed a novel nested-PCR assay that detects DNA specific for clinically important strains of Trichosporon in serum of patients with disseminated trichosporonosis. In this assay, two sets of oligonucleotide primers were derived from the sequence of 26S ribosomal RNA genes of T. asahii. The specific fragment was amplified from T. asahii and T. mucoides but not from other microorganisms. In a retrospective study using serum samples of patients with disseminated trichosporonosis, the specific fragment was detected in 64% (7 of 11). To treat this infection, we studied the efficacy of rhG-CSF alone and in combination with antifungal agents against disseminated trichosporonosis in neutropenic mice. The results suggested that rhG-CSF might be a useful immunomodulator against Trichosporon infections and the therapeutic outcome might be better when used in combination with antifungal agents.

View full abstract

Methods for the diagnosis of cryptococcosis have been established, including serotyping and serodiagnosis. Slide agglutination tests with factor sera, the phenol oxidase test, and the growth test at 37°C are used for rapid identification of Cryptococcus neoformans. We identified 140 strains and found that 86, 10, and 4% of the isolates were serotypes A, D, and A-D, respectively. Twelve of 14 serotype D strains were isolated from cutaneous cryptococcosis. The most reliable method of serodiagnosis is the latex agglutination (LA) test for detection of polysaccharide antigen combined with protease pre-treatment. The LA test is also used for prognosis. The clearance of cryptococcal polysaccharide antigen often takes a few years after treatment. To model the persistence of cryptococcal polysaccharides, we examined the clearance of antigen from the blood of rabbits injected with polysaccharide. The distribution and elimination half-lives of the antigen suggest the prolonged survival of C. neoformans.
Recently, the number of cases of C. albidus and C. laurentii has been increasing. The antigenic pattern and the sensitivity of C. albidus in the LA test are the same as that of C. neoformans serotype A. In contrast, C. laurentii does not react with factor sera for C. neoformans and the reactivity with sensitized latex is extremely low. These results were supported by the chemical structures of polysaccharides from these species. We should consider non-neoformans cases in both the identification of isolates and in serodiagnosis.

View full abstract

Restriction fragment length polymorphism (RFLP) in mitochondrial DNA (mtDNA) of clinical and environmental isolates of Sporothrix schenckii was investigated. Among mtDNA RFLP patterns with Hae III, of 14 environmental isolates morphologically identified as S. schenckii, only 2 isolates were confirmed as S. schenckii, while of more than 500 clinical isolates, all were confirmed to have this condition. Therefore, RFLP analysis of mtDNA is essential for the identification of environmental, but not clinical, isolates of S. schenckii.
Isolates of Sporothrix schenckii were classified into 23 mtDNA types (Types 1-23) based on mtDNA RFLP patterns with HaeIII and clustered into two major groups by phylogeny, Group A (Types 1-3, 11, 14-19, 22 and 23) and Group B (Types 4-10, 12, 13, 20 and 21). Group A isolates are predominant in South Africa, North America, Central America and South America, while Group B isolates are predominant in Australia and Japan. In Japan, the relative distribution of the mtDNA types varied with geographic region: Types 4, 6 are comparatively abundant in West Japan (Kansai and Kyushu districts), Type 5 is comparatively abundant in East Japan (Tokai, Kanto and Tohoku districts) and Type 2 is abundant in the Hokuriku district. Type 1 is found only in the Hokuriku district.

View full abstract

Sixty-six new and used samples of horse bedding materials: 60 rice straws, 2 wheat straws, 2 timothy hays and 2 woodchips, were collected from horse breeding stables of 33 farms in Japan and examined for the presence of Emericella nidulans (E. nidulans; anam. Aspergillus nidulans). The incidence of E. nidulans in the bedding materials was 75.8% and there was no significant difference in detection of the fungus between the new and used materials (25 out of the 33 samples, respectively). The growth of E. nidulans isolated in sterilized rice straw culture was accelerated by the addition of water up to about Aw 0.94, which as determined to be the most favorable moisture content. The addition of 0.3% urea solution onto the sterilized rice straw culture also appeared to very effectively enhance its conidial and ascocarp formation. A significant influence of urea on conidial and ascocarp formation of E. nidulans isolates was confirmed by their cultures on a synthetic medium which had urea as the sole nitrogen. These results suggest that severe contamination of E. nidulans on new bedding materials can be hazardous and its proliferation can readily occur at the stable due to the enhancing effect of urine. This analysis is meaningful to elucidate a reservoir of E. nidulans as the causative agent of guttural pouch mycosis in horses.

View full abstract

Extracellular keratinase (Ekase) 48-, 34- and 31.5-kDa polypeptides, which were isolated from Microsporum canis and examined by immunoblotting reacted with a monoclonal antibody against Ekase of M. canis.
We analyzed the amino acid and determined the first 17 amino acid NH₂-terminal sequences of the 48-, 34- and 31.5-kDa polypeptides. These polypeptides had a high aspartic acid, glycine and alanine content, respectively. The first 17 amino acid residues of the 34-kDa polypeptide were homologous to those of thermomycolin. This indicated that the 34-kDa polypeptide of Ekase is homologous to the thermomycolin produced by Malbrachea pulchella. Furthermore, Ekase was very heat-stable in the presence of 50mM CaCl₂ at 55°C, since 50% of the initial activity remained. In contrast, no activity was detected after heating in the absence of CaCl₂. These results indicate a close relationship between dermatophytes and M. pulchella.

View full abstract

The first cases of tinea corporis with Arthroderma benhamiae in Japan are reported. A 7-year-old girl and a 30-year-old mother in Shimane prefecture suffered from dermatophyte infections on the neck, shoulder, arms and leg. Three isolates from the two patients and a rabbit by which they supposedly were infected, were identified as Trichophyton mentagrophytes. On the bases of mating tests using the tester strains of both the African race and the Americano-European race of A. benhamiae, they were identified as A. benhamiae African race mating type (-). Our results are the first to indicate that both races of A. benhamiae exist in Japan.

View full abstract

We report two cases of Trichophyton mentagrophytes infection. Case 1: A 10-year-old girl visited Tokyo Electric Power Hospital in June 1994 for evaluation of an erythematous lesion on her head. Three months of topical steroid therapy exacerbated the lesion with pustular formation. Histopathological and mycological examination revealed that the patient had tinea capitis caused by T. mentagrophytes. T. mentagrophytes was also isolated from her pet, a hamster. Case 2: A-14-year-old girl was referred to Shonan Clinic in January 1996 with scaly erythema on her face. She had been treated with neticonazole hydrochloride at another clinic, but the lesion became worse. Direct microscopic examination of the scale was negative at that time, so treatment with topical steroid was started. After 10 days, the lesion was almost cured, but one month later it recurred with an annular distribution. KOH preparation of the scale revealed mycelia and T. mentagrophytes was isolated on culture. T. mentagrophytes was also isolated from her pet, a chinchilla. In both cases, the oral administration of itraconazole at 50mg/day was effective. The isolated pathogen was identified as Arthroderma vanbreuseghemii with species-specific primers of chitin synthase 1 gene. T. mentagrophytes is one of the most common dermatophytes isolated from man and animals. Rodents like the hamster and the chinchilla have recently become popular as pets in Japan. We should be aware that rodents may carry this kind of fungal pathogen as they become even more popular as pets.

View full abstract