Effect of Age of a Specific Medium on Morphology of Colonies of Certain Pathogenic Fungi. ∗

Abstract

In this work batches of media were allowed to age at laboratory temperature, planted with organisms and morphological differences observed. In aging, the medium loses water and the nutrient concentrates so that while the ratio of ingredients is probably approximately the same the moisture content, as will be noted below, becomes much less. Our routine W medium, consisting of 4% peptone, 1% dextrose, 1 1/2% agar and adjusted to pH 5.6, was used. The age of media which was placed on laboratory bench tops varied by approximately 10-day intervals from fresh medium to 90-day-old medium.

The following representative fungi and 2 non-pathogenic saprophytes, Lichtheimia sp. and Scopulariopsis brevicaulis, were studied: Achorion schoenleinii, Acladium castellani, Candida candida, Endodermophyton indicum (Castellani), Endodermophyton tropicale, Endomyces capsulatus, Endomyces dermatitidus, Epidermophyton cruris, Epidermophyton inguinale, Epidermophyton rubrum (Castellani), Glenospora gammeli, Geotrichum bachmann, Indiella americana, Microsporon audouini, Microsporon felineum, Microsporon gypseum, Monosporum apiospermum, Monilia albicans, Oöspora humi, Sporotrichum schenkii, Trichophyton balcaneum (Castellani), Trichophyton crateriforme, Trichophyton decalvans (Castellani), Trichophyton granulosum, Trichophyton gypseum, Trichophyton gypseum asteroides, Trichophyton gypseum lacticolor, Trichophyton interdigitale, Trichophyton japonicum, Trichophyton louisiana (Castellani), Trichophyton niveum, Trichophyton purpureum, Trichophyton sulfureum, Willia anomala.

With age there was retraction and contraction of the medium. This was accompanied by less space for the growth to spread over, with some resultant lessening of growth. In 13-weeks-old medium there was enough shrinkage so that after a month of growth only a dry scale remained. Yet growth occurred in all instances with the exception of Trichophyton louisiana. Thirteen-week growths were smaller, much dried yet retained in most instances some of the typical morphology seen on fresh medium. In many instances the growths on 11- and 12-week media were much dried but showed good differentiation.