328 An Introduction to Medical Mycology 



hours of such incubation at room temperature, buckling may be noted. 

 The organisms are from 8 to 20 microns or more in diameter. When a 

 stained histologic section is examined, the buckling organism may be 

 noted in giant cells or in the granulation tissue. 



(c) Cultural characteristics.— According to Martin and Smith, both 

 dextrose agar and blood agar should be used in the attempt to culture this 

 fungus. The dextrose agar is left at room temperature, and the blood agar 

 is incubated at 37 C. 



The colonies which develop on the incubated blood agar are small, com- 

 pact and shiny. On dextrose agar the colonies are at first smooth and grayish 

 but soon become filamentous and white, with a central umbo. A peripheral 

 moist yeastlike zone is usually present. The organism grows moderately 

 fast and in two or three weeks has developed to a good size. On blood agar, 

 the subsurface growth is much greater. The yeastlike form may be main- 

 tained for long periods by being subcultured on blood agar and kept in 

 the refrigerator. With age, the growths become brown and the surface may 

 crack. 



(d) Culture mount.— Material from (yeastlike) colonies grown on blood 

 agar reveals budding cells ( blastospores ) and occasional short rods with 

 approximately the diameter of the other cells (Martin and Smith). Ma- 

 terial from colonies grown on the dextrose agar shows mycelium with lateral 

 conidia and large round cells ( chlamydospores ) . Racquet mycelium may 

 also be noted. 



(e) Filtered ultraviolet rays.— The appearance is not changed in 

 young or in old colonies. No fluorescence is noted. 



(f) Animal inoculation.— According to Spring, the mouse is most sus- 

 ceptible, the rat is less so, and it is difficult to infect rabbits and guinea- 

 pigs. The gonads are most vulnerable and are the usual site of inoculation. 

 Generalization of the infection, even in mice, does not always occur; 

 death should not be expected. The formation of abscesses may be con- 

 sidered a "take." Using an intravenous technic, Heilman was able to pro- 

 duce a uniform and rapidly fatal infection in mice. The time of death 

 was directly related to the number of organisms administered. Death was 

 clue to embolic pneumonia. 



(g) Differential diagnosis.— If the buckling micro-organism is ob- 

 served in a direct preparation, the diagnosis may be made with certainty. 

 There is a single bud in contradistinction to the multiple buds of P. 

 brasiliensis. Actinomycosis is ruled out by the absence of granules in the 

 pus. In C. immitis there is a variation in the size of the cells, budding 

 is not present, and endospores may be present. Again, animal inoculation 

 may be valuable in case of doubt. 



