Microsporum racemosum: first isolation in the United States

What is believed to be the first isolation in the United States of the dermatophyte Microsporum racemosum (2) was obtained from a 79 year old white male. The patient had numerous excoriations on the forehead, scalp, and nape of the neck. (Fig. 1) A culture of scrapings from the forehead grew out a flat, granular, cream-colored colony with a red cherry-colored pigment on the reverse. (Fig. 2). The growth was exceedingly rapid, reaching a thallus of 40 mm. in diameter within 15 days. On microscopic examination the organism was found to produce numerous echinulated macroaleuriospores, (Fig. 3,5) as well as numerous microaleuriospores which are striking in appearance, occurring in wand-like clusters and being frequently stalked. (Fig. 4,5) The macroaleuriospores are quite large, achieving over 60 microns in length and 15-16 microns in diameter. The colony and microscopic appearance was consistent with Borelli's description, with the exception of the wall of the macroaleuriospore. Borelli described the wall as being thin and very similar to M. gypsum, while in the isolation from Illinois, the wall was moderately thick. Drs. Ajello and Padhye of the U.S. Public Health Service, Center for Disease Control, Atlanta, Georgia confirmed the identification.