332 An Introduction to Medical Mycology 



(f) Animal inoculation.— Mice, rats, guinea-pigs and dogs develop 

 fatal generalized infections when a suspension of the fungus is injected 

 intraperitoneally. Monkeys are similarly susceptible when given intra- 

 venous injections (Howell). 



(g) Differential diagnosis.— When blood or other materials are exam- 

 ined, the intracellular oval or round yeastlike organism is characteristic. 

 The cultural growth on dextrose agar is similar to B. dermatitidis. How- 

 ever, a culture mount will demonstrate the typical chlamydospores which 

 will differentiate the two organisms. 



BIBLIOGRAPHY 



Conant, N. F.: Cultural study of life-cycle of Histoplasma capsulatum Darling 1906, J. Bact. 



41:563, 1941. 

 Howell, A., Jr.: Medical Mycology, a mimeographed outline for postgraduate students in 



tropical medicine, January, 1943. 



24. COCCIDIOIDES IMMITIS 



There is general agreement that this organism is solely responsible for 

 the disease coccidioidomycosis, as seen in this country. 



(a) Immune reaction.— Dickson and others have held that the cuta- 

 neous reaction to coccidioidin is specific. 



(b) Collection of material.— Care must be taken that accidental in- 

 fection of laboratory workers does not occur. The chief danger appears 

 to be that spores from an old culture may be inhaled. Laboratory workers 

 should wear masks while handling this micro-organism. The person obtain- 

 ing a specimen from a patient should wear rubber gloves, although infec- 

 tion from man to man is unknown. As with other fungous diseases, ma- 

 terial from a fresh lesion is preferable, and avoidance of grossly contami- 

 nated areas is to be desired. 



(c) Microscopic: features.— The micro-organism is to be found in free 

 pus and in histologic sections. It consists of a sphere with a double- 

 contoured capsule (ascus?) and is from 5 to 60 or more microns in diam- 

 eter. Within the organism are from six to 20 round bodies (endospores, 

 ascospores?). Rupture of the capsule results in dissemination of these 

 spores and accounts for the sometimes rapid spread of the disease to areas 

 remote from the primary focus. It is not usually necessary to stain the pus 

 in order to demonstrate the micro-organism. As in demonstrating the ray 

 fungus, a cover slip is dropped over a drop of pus on a clean slide and 

 immediately examined. If the specimen is sputum or spinal fluid, the ma- 

 terial may be concentrated by centrifugation and then examined. 



(d) Cri/iiRAi. characteristics.— The material is streaked on the sur- 



