DEHYDRATED CULTURE MEDIA 69 



BACTO 



HEART INFUSION AGAR 



DEHYDRATED 



This medium is recommended in "Methods and Standards for the Production 

 of Certified Milk" for the preparation of Blood Agar plates for the recognition 

 and differentiation of hemolytic streptococci. Such Blood Agar plates may also 

 be used for the total bacterial count of certified milk. A complete discussion of 

 Bacto-Heart Infusion Agar is given on page 87. 



BACTO 



BEEF LACTOSE AGAR (B25) 



DEHYDRATED 



Beef Heart, Infusion from 450 g. 



Proteose Peptone, Difco 5 g. 



Bacto-Lactose 10 g. 



Bacto-Agar 15 g. 



Bacto-Beef Lactose Agar is prepared according to the formula for Beef Infu- 

 sion Lactose Agar recommended by the subcommittee on Microbiological 

 Methods for Examining Butter^ of the American Dairy Science Association for 

 determining the total bacterial count in the microbiological analysis of butter. 

 This medium, with 0.5 ml. of sterile skim milk added to each plate at the time 

 of pouring, may be used for the detection of proteolytic colonies. 



While much of the spoilage in butter is due to the presence of molds and yeasts, 

 bacteria are also capable of causing extensive losses due to the production of 

 undesirable flavors. The subcommittee on Microbiological Methods for Examin- 

 ing Butter of the American Dairy Science Association in its report has included 

 methods for the bacterial count and the detection of proteolytic and lipolytic 

 bacteria as well as for determination of yeasts and molds. In this report the 

 medium recommended for the total bacterial count is Beef Infusion Lactose 

 Agar. 



To rehydrate the medium, suspend 45 grams of Bacto-Beef Lactose Agar in 

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

 pletely. 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 

 6.8. 



One pound of Bacto-Beef Lactose Agar will make 10 liters of medium. 



* J. Dairy Science, 16:289:1933. 



BACTO 



NUTRITIVE GASEINATE AGAR (B27) 



DEHYDRATED 



Bacto-Peptonized Milk 7 g. 



Bacto-Isoelectric Casein 3 g. 



Special Agar 12 g. 



Bacto-Nutritive Caseinate Agar is recommended for the differential plate 

 count of milk. On poured plates of this medium inoculated with dilutions 

 of milk and other dairy products, strong and weak acid forming colonies and 

 peptonizing colonies may be readily differentiated from one another. 



