190 



INFECTIONS CAUSED BY MOLDS 



cavity commonly presents lesions, and vegetative endocarditis and 

 ulcerative enteritis have been reported. 



Diagnosis. Histoplasmosis should be suspected in undiagnosed 

 cases presenting the foregoing characteristics. Its diagnosis depends 

 upon the laboratory demonstration of the fungus in cells of the 

 reticuloendothelial system or its isolation in culture. Histoplasma 

 may be present in the circulating blood, and it can be demonstrated 



Fig. 96. Histoplasmosis: left, Histoplasma capsulatum in blood smear (impres- 

 sion smear of liver of hamster with experimental histoplasmosis, Giemsa stain, 

 X900) ; right, spores ("chlamydospores") of H, capsulatum. 



during life in smears of blood or of sternal bone marrow stained by 

 Giemsa's or Wright's methods. Mucous membrane lesions of the 

 oral cavity, when present, are probably better sources of material 

 for smears. For its isolation in culture blood, sternal bone marrow, 

 or material from ulcers should be spread on the surface of Sabouraud 

 agar slants which should then be incubated at 30° C. or on blood 

 agar incubated at 37° C. A skin-testing antigen can be prepared 

 by growing the fungus for 3 months on the synthetic broth medium 

 used in the preparation of coccidioidin. When 0.1 ml. of a dilution 

 of 1:1000 of the sterile filtrate from such a culture is injected intra- 

 cutaneously into the patient or into infected guinea pigs the tuber- 

 culin type of delayed reaction is observed. The antigen is known 

 to cross-react with blastomycosis and occasionally with other my- 



