Dermatophyte test medium screening limitations.

Abstract

To the Editor.— Jacobs and Russell recently reported in a LETTER TO THE EDITOR (224:1649, 1973) that the systemic zoopathogens Histoplasma capsulatum, Blastomyces dermatitidis , and Coccidioides immitis , as well as dermatophytes, induce a color change when grown on dermatophyte test medium (DTM). They suggested that in regions where these zoopathogens are endemic, DTM could be employed as a screening test to rule out the fungi as causative agents in cases of undefined upper respiratory tract infections. Although I have noted similar results with respect to the development of systemic pathogens, I have also observed that common airborne saprophytes can cause a color change on DTM. In contrast to the instances of saprophytic contamination noted by Taplin et al, 1 I found that many of these molds are capable of inducing a change from straw yellow to deep red within seven to nine days. Moreover, they are morphologically indistinguishable in gross DTM