304 An Introduction to Medical Mycology 



granular or powdery varieties may produce follicular infections of the 

 scalp and other parts of the body of acutely inflammatory nature. T. gyp- 

 seum is one of the causes of kerion. 



(1)) Immunologic reactions.— Patients who show a primary inflam- 

 matory reaction to this fungus also react to trichophytin. It is our impres- 

 sion ( our experience is yet too limited to be certain ) that the powdery type 

 sensitizes the skin to a greater degree than the fluffy type and that allergic 

 reactions (ids) are more common with the powdery type. 



(c) Microscopic features.— Trichophyton gypseum is an ectothrix 

 Trichophyton; the fungus is external to the hair, and the spores tend to 

 form chains. The spores are similar in size to those of the Microspora. In 

 scales, macerated skin and nail tissue the organisms appear as chains of 

 spores or as segmented mycelium with little branching. 



(d) Cultural characteristics.— (1) The type usually isolated appears 

 first as a white and fluffy growth. After 10 days to two weeks the surface 

 becomes velvety, flat and light buff or buff-yellow. There is usually a 

 boss at the center, and occasionally there are a few irregular folds. (2) The 

 granular or powdery type of growth is characterized by its powdery or 

 velvety surface, with fluffy changes developing as it ages. The color is light 

 buff or maize-yellow. The rate of growth is moderately fast. ( 3 ) The white 

 fluffy type of culture (T. interdigitale ) begins as a downy feather-like 

 projection; the growth rapidly develops and within two weeks almost cov- 

 ers an agar slant. It is almost pure white. The growth shows many aerial 

 hyphae. (4) The white compact type (T. niveum) at first grows out white 

 and fluffy. The surface then becomes compact, and irregular elevations and 

 depressions make their appearance. The snow-white color is retained. 



(e) Culture mount.— (1) The ordinary type is characterized by spirals. 

 Fuseaux with blunt ends are present in small numbers. Nodular organs, 

 pectinate bodies, racquet mycelium and chlamydospores are also to be 

 noted. The mycelium is septate and usually branched. Microconidia are 

 also to be seen as thyrsi and as grappes. ( 2 ) The granular type shows few 

 spirals. There are numerous blunt-end fuseaux with dense masses of micro- 

 conidia produced in grappes and thyrsi. Chlamydospores and racquet 

 mycelium are also present in the subsurface growth. (3) In the fluffy type 

 (T. interdigitale) the aerial growth consists of a large percentage of vege- 

 tative filaments. There are limited numbers of microconidia in small clus- 

 ters. Nodular organs and racquet mycelium may be found. Spirals and 

 fuseaux are usually absent. (4) In the white compact type (T. niveum) the 

 findings are essentially the same as in the fluffy type. 



(f) Filtered ultraviolet rays.— There is no fluorescence to be detected 

 when follicular infections caused by ectothrix Trichophyta are examined 



