312 An Introduction to Medical Mycology 



51 and 60 years inclusive, 75 per cent of apparently normal persons show 

 a cutaneous reaction to the injection of an extract of M. albicans. 



(c) Microscopic features.— In material from some untreated lesions, 

 such as those of thrush or erosio interdigitalis blastomycetica, a tangled 

 network of fine mycelium with clusters of spores may be noted. In scrap- 

 ings from nails and many other locations, only a few hyphae or budding 

 cells may be observed, and frequently the results from the potash prepara- 

 tion are uncertain. 



(d) Cultural characteristics.— The growth on dextrose agar is mod- 

 erately fast and is first noted after two or three days. It is wet, pasty and 

 cream-colored. The surface is usually smooth except near the center of the 

 colony, where it has a honeycombed appearance due to ruptured air 

 bubbles. On corn meal agar, a deep stab with a needle containing the 

 cultural growth results in the characteristic picture of an inverted pine 

 tree. It is notable that pure cultures are the rule. It seems that there is 

 marked inhibition of other micro-organisms in the presence of M. albicans. 



(e) Culture mount.— Mycelial development is best seen in material from 

 colonies grown on corn meal agar. Clusters of spores in rounded masses are 

 to be observed along the hyphae, and chlamydospores also develop. No 

 ascospores are present. 



(f) Filtered ultraviolet rays.— The appearance of colonies changes 

 little from their appearance in normal light; the color is clear, dull and 

 yellowish brown. 



(g) Animal inoculation.— Intracutaneous inoculation in guinea-pigs 

 causes a mild inflammatory reaction. Rabbits are killed by the intravenous 

 injection of 1 cc. of the 1:1,000 suspension, miliary abscesses being pro- 

 duced in all parts of the animal (Benham). 



( h ) Fermentation reactions.— Acid and gas are produced with dextrose, 

 levulose and maltose but not with saccharose (Benham). 



(i) Agglutination reactions.— Agglutination is seen when a serum is 

 prepared against a known strain of the yeast (Benham). 



(j) Differential diagnosis.— Cryptococci do not develop mycelium, and 

 other fungi in the monilia group may be distinguished from M. albicans by 

 the absence of chlamydospores when they are grown on corn meal agar. 

 Mycoderma may usually be recognized by its gross appearance in culture; 

 a culture mount reveals arthrospores. Endomyces and Saccharomyces form 

 ascospores; the former also develops mycelium. 



14. MALASSEZIA FURFUR (MICROSPORUM FURFUR) 



This is the cause of tinea versicolor, and either this fungus or one closely 

 related is the source of some cases of tinea flava and achromia parasitaria. 



