294 An Introduction to Medical Mycology 



(b) Immunologic reactions.— A large majority of patients with favus 

 give negative reactions to the intracutaneous test with trichophytin. Occa- 

 sionally a mild response may be noted. 



(c) Microscopic features.— Large spores in chains may be found within 

 the hair substance. Air spaces may also be noted in the hair, and air bubbles 

 may be attached to it; this should always direct suspicion toward this 

 organism. If a scutulum is examined, a mass of sporulated hyphae will 

 be found. Material from the superficial lesions of the smooth skin reveals 

 a sparse number of hyphae. The findings in material from infected nails 

 resemble those of other organisms, i.e., chains of spores. 



(d) Cultural characteristics.— The rate of growth is slow; sometimes 

 three weeks elapse before the primary colony has developed sufficiently to 

 be recognized. The growth is compact and smooth and presents a char- 

 acteristic waxy appearance. The surface is markedly uneven. Pleomorphism 

 is uncommon. The colony grows down into the medium and in time pro- 

 duces cracking of the agar. 



(e) Culture mount.— Favic chandeliers are noted; they are diagnostic. 

 Chlamydospores in large numbers may also be observed. 



(f) Filtered ultraviolet rays.— Infected hairs show a greenish fluo- 

 rescence but are less luminous than hairs infected with Microsporum. The 

 cultural growths have a dull clear olive-gray appearance throughout. 



(g) Animal inoculation.— Guinea-pigs may be infected. The organism 

 is also inoculable into rats, mice, cats and rabbits (Dodge). 



(h) Differential diagnosis.— The infected hairs are not always short. 

 The appearance of a direct mount reveals an endothrix infection. The 

 number of filaments is less than with other organisms; the presence of air 

 bubbles is also highly suggestive, and the irregular segmentation of the 

 filaments is characteristic. On culture, little difficulty is experienced in 

 differentiating other growths. The favic chandeliers visible in a culture 

 mount are seen in no other cultural growth. 



6. TRICHOPHYTON ALBA (FAVIFORME) 



An uncommon isolate, the usual clinical response is an intensely in- 

 flamed, boggy, rapidly spreading eruption of the smooth skin. A history of 

 contact with infected animals may be significant. 



(a) Immune reactions.— The trichophytin test elicits strong reactions. 



(b) Microscopic features.— Masses of large spores in filaments may be 

 observed. 



(c) Cultural CHARACTERISTICS.— The growth is slow. Small yellow glab- 

 rous or waxy colonies, mostly subsurface, gradually form some areas of 



