DIAGNOSIS 



145 



be found more readily. Pus or sputum may be placed on a slide 

 under a cover slip and examined directly. Often the fungus can be 

 demonstrated more easily if the material is placed on the slide and 

 mixed with a drop of 10 per cent sodium hydroxide. This digests 

 the tissue elements while the fungus is relatively resistant. The 

 appearance of the fungus will be described in a later paragraph. 

 Sputum contains so many diverse elements that there may be some 

 difficulty in finding the fungus. In such cases isolation in cultures 



Fig. 72. Coccidioides immitis in sputum after sodium hydroxide digestion: 



left, an immature spherule and a mature sporangium from which spores have 



escaped; right, a nearly mature sporangium. 



may be more productive. This is usually relatively easy because of 

 the rapid growth of the fungus. Sputum. should be streaked out on 

 the surface of agar slants. The digestion and concentration methods 

 used in isolating the tubercle bacillus kill Coccidioides, but sputum 

 may be treated with 0.05 per cent cupric sulphate which destroys 

 most of the bacteria. American Sabouraud agar or a selective cul- 

 ture medium devised at Stanford University may be used. The 

 latter consists of 1 per cent ammonium chloride, 1 per cent sodium 

 acetate, 0.8 per cent tribasic potassium phosphate, and 2 per cent 

 agar. The medium is autoclaved for 10 minutes at 15 pounds pres- 

 sure and 0.04 per cent cupric sulphate is added just before pouring. 

 If plates are used in the isolation of Coccidioides the fungus should 

 be transferred to agar slants soon after it appears and the original 

 plate cultures must be autoclaved promptly. The fungus begins to 

 produce spores usually within 8 to 10 days and there is grave danger 

 of laboratory infection if old plate cultures are opened. It is prob- 



