Shigeru Fujita

Extracellular Vesicle Formation and Biosurfactant Production by Serratia marcescens

Summary: Pigmented and non-pigmented strains of Serratia marcescens produced extracellular vesicles and had wetting activity when grown at 30°C but not at 37°C. Light microscopy showed that the red pigment was present in vesicles and intracellular granules. Electron microscopy revealed the presence of vesicles surrounded by the bacterial membrane. Three lipids having the wetting activity, W1, W2 and W3, were isolated by thin-layer chromatography of lipids from different strains of S. marcescens. Dispersions of the isolated wetting agents had small contact angles on a polystyrene surface and the ability to lower surface tension. Wetting agent W1 was the aminolipid serratamolide. Wetting agents W2 and W3 were also aminolipids but were shown to be different from serratamolide by chemical analyses. Wetting agent and prodigiosin (in a pigmented strain) were the main lipids of isolated vesicles.

Experimental tinea pedis induced by non-abrasive inoculation of Trichophyton mentagrophytes arthrospores on the plantar part of a guinea pig foot

Arthrospores of Trichophyton mentagrophytes were inoculated on to the plantar part of a guinea pig foot by a newly devised non-abrasive method. Anthropophilic and zoophilic isolates required inocula of 280 and 80 arthrospores to infect 50% of inoculated feet, but much larger inocula (5 X 10(4)) were used to establish infection consistently in all feet. Anthropophilic isolate NTM-105 invaded only the upper two-thirds of the horny layer and induced no inflammatory responses. On the other hand, zoophilic isolate SM-110 invaded the whole horny layer and provoked strong inflammatory responses and clinical manifestations. Although the histological features and modes of fungal spreading in the guinea pig skin were quite different between anthropophilic and zoophilic isolate infections, infecting fungi were always recognized in the stratum corneum of all inoculated feet throughout the observation period longer than 6 months. Thus, two types of persistent infections with T. mentagrophytes were established as a guinea pig model of tinea pedis.

Simultaneous demonstration of infecting fungi and DNA‐synthesizing epithelial cells in the skin

Summary. An excellent staining method to demonstrate in vivo dermatophytes and DNA‐synthesizing cells in the skin is described. Deparaffinized sections of guinea pig skin, infected with dermatophytes and given bromode‐oxyuridine (BrdU) by intraperitoneal injection, were used. Periodic acid—Schiff (PAS) stain in combination with an immunohistochemical stain using anti‐BrdU monoclonal antibody allowed simultaneous visualization of fungi and DNA‐synthesizing epithelial cells in the skin. Many epithelial cells near the infecting fungi in follicles and interfollicular skin were labelled with BrdU. Only a few BrdU‐positive cells were observed in the skin of uninfected animals.