272 An Introduction to Medical Mycology 



should be repeated in order to insure accuracy. If the drug to be tested is 

 thermolabile, the agar and drug should be sterilized separately and then 

 mixed. The drug may be freed from contamination by ultrafiltration. 



(b) Broth dilution method.— Similar to the first method, this procedure 

 utilizes a liquid (broth) medium. Chemicals to be tested show more effec- 

 tive fungicidal power in this medium than when agar is used. 



(c) Disk diffusion method.— A series of dilutions is made of the drug 

 to be tested. Filter paper disks of standard size are impregnated with the 

 various dilutions and placed on the agar plate previously seeded by the test 

 organism. An accurate measurement is made of the zone of inhibition. 



2. TESTING FUNGICIDAL POWER 

 (Method of Schamberg and Kolmer; McCrea) 



Cultural growths free from agar are shaken with glass beads in sterile 

 saline solution for 10 minutes. The density is determined by comparison 

 with a standard such as tube 5 of the McFarland nephelometer. A solution 

 of the drug to be tested is diluted in distilled water. Equal parts of varying 

 dilutions of the drug and of the suspension of culture are mixed and kept 

 at a temperature of 20 C. Several loopfuls are transferred to slants of 

 dextrose agar at intervals of 15 minutes, one hour, three hours and 24 hours. 

 Control tests should be made, saline solution being used instead of the 

 diluted drug. The results will be apparent within two to three weeks. 



BIBLIOGRAPHY 



McCrea, A.: Proposed standard method for evaluation of fungicides, J. Lab. & Clin. Med. 



17:72, 1931. 

 Peck, S. M.; Rosenfeld, H.; Leifer, W., and Bierman, W.: Role of sweat as fungicide, 



with special reference to use of constituents of sweat in therapy of fungous infection, Arch. 



Dermat. & Syph. 39:126, 1939. 

 Schamberg, J. F., and Kolmer, J. A.: Studies in chemotherapy of fungous infections, Arch. 



Dermat. & Syph. 6:746, 1922. 



