An Improved Slide Culture Technique for the Study and Identification of Pathogenic Fungi.

The microscopic identification of many pathogenic fungi still depends almost wholly upon morphology, especially upon the size, location, and arrangement of individual spores or groups of spores. The usual procedure is to examine teased wet-mount preparations. These have a number of disadvantages, however. The structures depended upon for the recognition of such fungi as Blastomyces dermatitidis or Sporotrichum 8chenkii, for example, are often so distorted or disarranged in these teased mounts that identification is made difficult or impossible, particularly for persons unfamiliar with this technique. Slide cultures, on the other hand, when suitably prepared, make possible the definite recognition of these genera, and also help materially with the classification of other varieties of fungi. Use of the available slide culture techniques (Henrici, 1930; Brown, 1942; Lewis and Hopper, 1943), however, is beset with numerous difficulties. None of these methods is suitable for rapid identification of pathogenic fungi. The present paper describes an improved slide culture technique which is relatively easy to oarry out and is useful for practical diagnostic work in mycology, as well as for classroom teaching. Since pathogenic fungi grow slowly, and hence may easily be crowded out by more rapidly developing contaminants, provision has been made to exclude such contaminating organisms. The method also makes possible the direct inoculation of the culture slide with a large inoculum. This has been found to be necessary to insure growth of pathogenic species. Special attention also has been given to the nature of the medium for the microculture. Since identification depends to a large degree upon the presence of typical spores, it is important that the medium used stimulate early and abundant sporulation. Lastly, this improved slide culture technique is designed to permit the easy preparation from the culture of stained slides which preserve intact the morphological features of the fungus. These slides are valuable for making photomicrographs and are especially useful for teaching purposes.