DEHYDRATED CULTURE MEDIA 87 



Medium in 100 ml. cold distilled water. Mix thoroughly and allow to stand for 

 15 minutes until all the particles are thoroughly wetted, and while maintaining an 

 even suspension distribute into tubes. The medium may also be rehydrated by dis- 

 tributing 1.25 grams into test tubes, adding 10 ml. cold distilled water, and mix- 

 ing thoroughly, allowing to stand to insure thorough wetting of all particles. 

 Sterilize in the autoclave for 15 minutes at 15 pounds pressure (121°C.). To 

 prevent blowing of medium, avoid rapid release of pressure in the autoclave 

 after sterilization. Properly prepared tubes of Bacto-Cooked Meat Medium 

 should have a well defined layer of meat particles overlaid by a clear, amber- 

 colored supernatant liquid. As soon as the sterile medium has cooled to 37 °G. 

 it is inoculated by loop or pipette, introducing the inoculum well into the meat 

 layer. The final reaction of the medium will be pH 7.2. 



Tubes of Cooked Meat Medium not used the day they are prepared should be 

 placed in a boiling water bath or flowing steam for a few minutes to drive out 

 dissolved oxygen, then cooled to 37°C. and inoculated. 



One pound of Bacto-Cooked Meat Medium will make 3.6 liters of medium. 



iCentr. Bakt., 7:509:1890. ^ J. Path. Bact., 21:344:1917. 



sCentr. Bakt., 38:619:1905. 'J. Bact., 4:149:1919- 



3 Centr. Bakt., 25:513:1899. 8 standard Methods for the Examination 



*Von Hibler: Untersuchungen ueber die of Dairy Products, 9th Edition: 192: 1948. 



Pathogen Anaeroben, 1908. s Diagnostic Procedures and Reagents, 3rd 



6 J. Path, Bact., 20:327:1916. Edition: 17:1950. 



BACTO 



HEART INFUSION AGAR (B44) 



DEHYDRATED 



Beef Heart, Infusion from 500 g. 



Bacto-Tryptose 10 g. 



Sodium Chloride 5 g. 



Bacto-Agar 15 g. 



Bacto-Heart Infusion Agar is a solid infusion medium recommended for gen- 

 eral laboratory use for the cultivation of many pathogenic bacteria. It can be 

 used as a base to which a large variety of materials, such as blood or carbo- 

 hydrates, may be added, giving media for many special purposes. It is a satis- 

 factory medium for mass culture of organisms, making it valuable in the prep- 

 aration of vaccines. Bacto-Heart Infusion Agar is recommended by the American 

 Association of Medical Milk Commissions^ for preparation of Blood Agar for 

 the recognition and differentiation of streptococci in the examination of certified 

 milk. 



Like infusion broth, a solid medium prepared with the extractives of fresh 

 meat and containing agar was used almost from the beginning of bacteriology. 

 Huntoon^ was one among the many to show that highly pathogenic organisms, 

 such as the meningococcus and pneumococcus, could be grown on an infusion 

 medium without enrichment. Bacto-Tryptose, as employed in this formula, is 

 better suited to the nutritional requirements of pathogenic bacteria than is Bacto- 

 Peptone which was used by Huntoon in the preparation of his "hormone" agar. 

 The blood culture method of Castaneda, as described in detail on page 113 

 under Tryptose Agar may be used with this medium. 



To rehydrate the medium, suspend 40 grams of Bacto-Heart Infusion Agar 

 in 1000 ml. of cold distilled water and heat to boiling to dissolve the medium 

 completely. Distribute in tubes or flasks and sterilize in the autoclave for 15 

 minutes at 15 pounds pressure (121°C.). The final reaction of the medium will 

 be pH 7.4. 



