PREPARATION OF MEDIA ii,,-17 



Beef liver infusion medium. Remove fat from 500 g. of fresh beef 

 liver, grind, and heat, with occasional stirring, in 1,000 ml. of tap 

 water for one hour in the Arnold sterilizer. Cool and strain through 

 cheese cloth. Restore filtrate to original volume and add 1% peptone 

 and 0.1% K2HPO4. Dry tissue (at 55° C. if available) as rapidly 

 as possible. Tube broth over several chunks of tissue. Use the 

 broth (before addition of peptone and phosphate) in the original 

 strength, or diluted five times. Sterilize 30 minutes at 15 lbs. pres- 

 sure. Avoid longer heating of medium as this diminishes its value 

 with respect to initiation of growth from small inocula. 



Use: Recommended especially for enrichment, from spore stocks or 

 other sources, of the butyric-butyl group and C. perfringens. May 

 replace beef heart medium for pathogenic types. Useful for enrich- 

 ment medium in detection of thermophilic contamination of sugar, 

 starch, canned foods, etc. (Sometimes difiiculty is encountered 

 with this medium and the following one due to a Gram-positive rod 

 which develops as a contaminant during the drying of the liver 

 tissue.) 



Corn Liver Medium. Add 50 g. of ordinary (white or yellow) corn meal and 10 g. 

 of dried liver powder^ to 1,000 ml. of tap water (McClung and McCoy, 1934). Heat in 

 flowing steam for 1 hour with occasional stirring. Remove from steam and cool al- 

 most to room temperature. Dispense in tubes, flasks, or bottles as may be needed. 

 Sterilize for 45 minutes at 15 pounds pressure. The resulting medium, on cooling, 

 should be semisolid with the coarser particles of corn settling to the bottom leaving a 

 2-3 cm. layer of starchy material at the top. 



Use: A useful enrichment medium in studies of anaerobic population of natural 

 samples. (It remains anaerobic throughout prolonged incubation periods) . Especially 

 suited for the butyric-butyl group, and recommended for the detection of thermophilic 

 contamination. A very inexpensive and convenient medium suitable for sampling 

 surveys and other studies involving a large number of tubes. Has some diagnostic 

 value, as certain of the butyl groups give a characteristic "head" (a slimy mass of un- 

 fermented cellulosic material raised and collected at the top of the liquid) in this 

 medium in contrast to the butyrics which usually do not give this reaction. 



2. MEDIA FOR PLATING FOR PURIFICATION 



For the pathogenic types a good medium can be made from the 

 liquid obtained by the infusion of beef heart or lean beef tissue, as 

 discussed above, either with or without 0.5% glucose or defibrinated 

 blood or both. Similarly, the butyric-butyl group grow well on a 

 solidified medium prepared from liver broth, with the addition of 

 0.5% glucose. 



T hi ogly collate agars. For the pathogenic types Reed and Orr 

 (1941) suggested two other media which may be prepared from de- 

 hydrated ingredients which are available commercially. One of 

 these is made by adding 2% agar (for surface colonies) or 0.75% 

 agar (for subsurface colonies) and 0.1% glucose to Brewer's thiogyl- 

 collate broth, adjusted to pH 7.6 before sterilization. (The medium 



^Dried liver powder. Difco Laboratories, Detroit, Michigan. 



