CHAPTER XXI 



Cultural Methods 



WHEN one wishes to determine the species of infecting micro- 

 organism, it is necessary to study its appearance and behavior on 

 artificial mediums. We believe that in the future cultural methods will 

 be more generally employed for the isolation of pathogenic fungi. The 

 routine technic is not too difficult for the practicing physician. Throughout 

 this book we have pointed out many times the obvious advantage of a 

 precise diagnosis. The type of treatment may depend entirely on the cul- 

 tural findings. It is indisputable that the patient will nearly always benefit 

 from the exact knowledge to be gained from cultural studies. Physicians 

 arc great!) indebted to Sabouraud, who established the pathogenic nature 

 of many species of fungi. He found that a culture medium which con- 

 sisted of French maltose (imported from Germany), Chassaing peptone 

 and agar supported growth of most fungi when they were incubated at 

 room temperature. He further demonstrated that there was a remarkable 

 uniformity in the gross cultural appearance of any given species of fungus 

 and that this was sufficient for its recognition in the majority of instances. 



During World War I, maltose could not be obtained. The limited supply 

 on hand was soon exhausted, so substitutes were used, with varying suc- 

 cess. Weidman and McMillan showed that crude American dextrose could 

 be used as a satisfactory substitute for maltose. Weidman and Spring found 

 that 16 of 18 species of fungi which they tested produced satisfactory 

 growths when Fairchild's peptone (an American product) was substi- 

 tuted for Chassaing peptone (a French product). Hodges also found 

 Fairchild's peptone suitable for use. Numerous synthetic mediums have 

 been proposed; in theory, a medium in which the exact chemical constitu- 

 ents are known is to be desired. Neither dextrose nor peptone is of constant 

 composition; minor variations in the medium often result in changes in the 

 characteristics of a fungous colony. Weidman and Spring rightly stated that 

 such a medium must prove its superiority over those now in use by being 



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