326 An Introduction to Medical Mycology 



(f ) Filtered ultraviolet rays.— No change in the appearance is to be 

 noted. 



(g) Animal inoculation.— Most laboratory animals are susceptible. 

 The white rat is usually employed as particularly vulnerable. The testes of 

 this animal usually become involved in the systemic infection. 



(h) Differential diagnosis.— The lack of results from a direct mount 

 should make one suspect the presence of this fungus and practically rules 

 out actinomycosis. The culture usually develops rapidly at room temper- 

 ature and grows out characteristically. The clusters of ovoid spores borne 

 at the ends of short side branches make the diagnosis certain. Blastomyces 

 dermatitidis and C. immitis may usually be seen in a direct mount. On cul- 

 ture both the latter micro-organisms produce white filamentous growths. 

 Both lack the groups of spores characteristic of S. schencki. In case of 

 doubt, animal inoculation will be helpful in obtaining a pure strain. 



BIBLIOGRAPHY 



Salvin, S. B.: Multiple budding in Sporotriehum schenckii Matruchot, J. Invest. Dermat. 

 9:315, 1947. 



22. BLASTOMYCES DERMATITIDIS 



Castellani, Spring, Benham and others have shown that yeastlike fungi 

 other than B. dermatitidis may cause granulomas resembling blastomycosis. 

 Blastomyces dermatitidis, however, is probably the organism chiefly con- 

 cerned in Gilchrist's disease and is to be searched for when blastomycosis 

 is suspected. The etiologic and clinical features of this disease have been 

 given on pages 197 to 203. Material from the newer lesions is preferable 

 for examination. 



( a ) Immunologic reactions.— Martin and Smith found that the majority 

 of patients with blastomycosis react strongly to a heat-killed vaccine made 

 from the yeastlike form of B. dermatitidis. A positive reaction is consid- 

 ered specific, although cross-sensitization has been reported with histoplas- 

 min and occasionally with other antigens. 



Martin found that the complement fixation test is specific. The antigen 

 is made from the growth which develops on blood agar. 



(1)) Microscopic features.— When pus or sputum is obtained, a fresh 

 preparation may be made by placing a drop of either material on a clean 

 slide and covering it with a cover slip. The use of potassium hydroxide is 

 not necessary unless the material is scanty. Budding thick-walled round 

 or oval granular cells may be seen. If the suspected organisms do not show 

 budding, the cover slip may be rimmed with petrolatum. After 24 to 48 



