CHAPTER X 

 PATHOGENIC YEAST-LIKE FUNGI 



Normal Occurrence of Yeasts in Man and Animals. Higher ani- 

 mals consume yeasts with their food, and these organisms have been 

 demonstrated frequently in the alimentary tracts of animals and man. 

 Saccharotnycopsis guttulatus is apparently a constant normal para- 

 site of the intestines of rabbits. Most of the species found in higher 

 animals, however, are undoubtedly transitory organisms, not multi- 

 plying to any great extent in the body. Anderson ^ demonstrated 

 that most species of yeasts are not injured by the digestive juices, 

 but pass through the alimentary tract, and he described a number 

 of species from human feces. Benham and Hopkins ^ isolated species 

 of Candida, Cryptococcus, Geotrichum (Mycoderma), Saccharo- 

 myces, and Zygosaccharomyces from feces of normal persons. Can- 

 dida albicans was isolated from 18 per cent and Geotrichum from 

 41 per cent of the cases examined. The frequent occurrence of yeasts 

 in or on the human body has not been sufficiently considered by some 

 authors who have described pathogenic yeasts. 



Pathogenic Yeasts. It is very difficult to analyze the extensive 

 literature on yeast infections in man. Many of the organisms re- 

 ported have not been yeasts, but fungi of the type of Candida 

 albicans. In many other cases the organisms have been so incom- 

 pletely studied or described that it is impossible to determine whether 

 the author was dealing with a true yeast or with a yeast-like form 

 of a mycelial fungus. A large number of cases have been reported 

 in which the pathogenicity of the fungus has been very imperfectly 

 established, the mere presence of the yeast being considered sufficient 

 evidence of its etiologic relationship to the disease. Where these 

 fungi have occurred alone in deep-seated lesions, such evidence may 

 be given weight, but in the numerous cases where yeasts have been 

 found in superficial skin lesions, in the mouth and throat, sputum, 

 or feces, associated with numerous other organisms, their presence 

 can hardly be considered as evidence that they are the cause of the 

 disease process under consideration. Even pathogenicity for labora- 

 tory animals, unless pronounced, should be considered guardedly, 



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