324 An Introduction to Medical Mycology 



(a) Immune reactions.— The agglutination reaction is considered reliable 

 by most observers. However, du Toit found that agglutination is produced 

 by the serum of normal individuals. The intracutaneous test is of value, and 

 a positive reaction is almost always present in patients with sporotrichosis. 



(b) Collection of material.— The organism is present in spore form 

 in pus. If the lesion is not ulcerated, the pus may be withdrawn with a 

 large caliber (no. 19) needle attached to a syringe. If ulceration has oc- 

 curred, fresh pus from under the overhanging edges should be secured by 

 gentle pressure and removed with a medicine dropper or a wire loop. 

 Some of the pus may be dropped on slides for direct examination, but it 

 is more important to transfer material to the surface of agar for cultures. 

 This is done by streaking the drop of pus across the surface of the agar by 

 means of repeated slashes with a sterile scalpel. 



(c) Microscopic features.— The organism is seldom seen in fresh prep- 

 arations. Lawless described a stain by which he was able to demonstrate 

 the spores in fresh pus. One observes no mycelium but only cigar-shaped 

 cells (Benham). It should again be mentioned that disappointment or 

 error may follow if total reliance is placed on this procedure. 



(d) Cultural characteristics.— The organism grows well in most labo- 

 ratorv mediums at room temperature and is readily identified. 



On dextrose agar, after five to seven days, there develops a moist growth 

 the size of a pinpoint, with a fine fringe. This slowly increases and in two 

 weeks is about 2.5 cm. in diameter and is usually jet black. The surface is 

 moist, and the central portion shows irregular convolutions. The border 

 may be smooth at first but later becomes ridged. The color is gradually 

 lost, becoming successively brown, tan and cream-colored in repeated sub- 

 cultures. The color may be partially restored by adding yeast to the culture 

 medium and incubating at 10 C. In old colonies, white excrescences appear 

 on the surface. The young growth has a rubbery consistency tending to 

 friability with increasing age. 



(e) Culture mount.— In the young colony, the mycelium is profuse, 

 fine and branching. Fewer hyphae are observed in the older colonies. 

 Pear-shaped conidia are present at irregular intervals along the course 

 of the mycelium and may also appear as terminal triads and tetrads. Single 

 spores may also be seen attached directly to the sides of the hyphae. The 

 groups of spores are attached by short stalks (conidiophores). The spores 

 vary in color with age and are apparently responsible for the color of the 

 colony. Salvin considers S. schencki to be one of the more pleomorphic 

 of the pathogenic fungi. On special mediums lie was able to recognize at 

 least four phases of development: yeastlike with single buds; yeastlike 

 will) multiple buds; "abortive-hyphal," and mycelial. 



