Characteristics of Pathogenic Fungi 329 



HI BLIOGB \l'in 



Benham, H. \\\: Fungi ol blastomycosis and coccidioidal granuloma, Arch. Dermat. & Syph. 



30:385, L934. 

 Casteli \\i. V. New vibriothrix, Proc. Soc. Exper. Biol. i\ Med. 26:543, L929, 

 IImimw, 1". R.; Experimental production of rapidlj Fatal blastomycosis in mice for testing 



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 Martin, 1). S.: Complement-fixation in blastomycosis, J. [nfect. Dis. 57:291, L935. 



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1936. 

 Spring, D.: Comparison ol seven strains ol organisms causing blastomycosis in man, |. [nfecl 



Pis. 44:169, 1929. 



23. HISTOPLASMA CAPSULATUM 



This fungus is the cau.sc> of histoplasmosis. Conant believes that it be- 

 longs among the Moniliaceae. 



(a) Imminologic reactions.— Sterile broth filtrates (histoplasmin) are 

 said to elicit both tuberculin-like (delayed) and immediate responses in 

 infected individuals. Cross-sensitization with blastomycin and coccidioidin 

 has been reported. 



(b) Microscopic features.— The specimen may be blood, mine, sputum 

 or aspirated material from a lymph node, the sternum or the spleen. The 

 material should be mounted both unstained and stained by Giemsa's 

 method. The micro-organisms appear as round or oval yeastlike cells, usu- 

 ally budding. They may be present in endothelial leukocytes. A pseudo- 

 capsule is detectable. The cells measure 2 to 4 microns in diameter. A 

 large vacuole and a large granule may be visualized. The oil immersion 

 lens should be used. 



(c) Cultural characteristics.— There are two cultural forms, de- 

 pending on the technical method used. When cultivated on dextrose agar 

 and incubated at room temperature, the colony is brown, glabrous, has an 

 irregular surface and grows slowly. With age it takes on a white cottony 

 appearance, particularly if the medium becomes dry. With some difficulty, 

 the micro-organism may become pasty and moist when cultivated on 

 sealed blood agar tubes at 37 C. 



(d) Culture mount.— Material taken from the glabrous and white cot- 

 tony growths shows septate, branching hyphae. A characteristic finding is 

 large, "thick-walled chlamydospores with a tuberculate sculpturing of the 

 outer wall" (Conant). These chlamydospores are best demonstrated in 

 specimens removed from mucoid growths which have developed on sealed 

 blood agar tubes at 37 C. 



(e) Filtered ultraviolet rays.— No characteristic fluorescence is 

 present. 



