DEHYDRATED CULTURE MEDIA 213 



organism employed is an essential part of the test. In addition to selecting the 

 proper strain, the previous environment, the age of the culture and size of the 

 inoculum are of prime importance in the satisfactory performance of the test. 

 Micro Assay Culture Agar has proved to be an excellent medium in which to 

 carry stock cultures of Lactobacilli and other test organisms used for microbio- 

 logical assay work, while Micro Inoculum Broth is recommended for the prepara- 

 tion of the inoculum. 



Stock cultures of the test organism are prepared by stab inoculation. It is de- 

 sirable to prepare stock cultures at least in triplicate at monthly intervals. One of 

 the transfers is saved for the preparation of stock cultures, and the others used 

 to prepare inoculum in Micro Inoculum Broth, for assay, as needed. Stock 

 cultures following incubation at 35-3 7 °C. for 24-48 hours should be kept in the 

 refrigerator at 2-6°C. 



To rehydrate the medium, suspend 47 grams of Bacto-Micro Assay Culture 

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

 medium completely. The medium is then distributed in 10 ml. quantities in 

 tubes of 16-20 mm. diameter. Sterilize in the autoclave for 15 minutes at 15 

 pounds pressure (121°C.). The tubes are then allowed to cool in an upright posi- 

 tion. Final reaction of the medium will be pH 6.7. 



One hundred grams of Bacto-Micro Assay Culture Agar will make 2.1 liters 

 of medium. 



BACTO 



MICRO INOCULUM BROTH (B320) 



DEHYDRATED 



Bacto- Yeast Extract 20 g. 



Proteose Peptone No. 3, Difco 5 g. 



Bacto-Dextrose 10 g. 



Monopotassium Phosphate 2 g. 



Sorbitan Monooleate Complex 0.1 g. 



Bacto-Micro Inoculum Broth is recommended for the cultivation of Lacto- 

 bacilli used in microbiological assays. It is of particular value in the preparation 

 of the inoculum for these tests. 



Bacto-Micro Inoculum Broth may be employed in preparing the inoculum of 

 Lactobacilli used in microbiological assay. This medium eliminates the necessity 

 of using various basal media for this purpose. Subcultures of Lactobacilli are 

 made from Bacto-Micro Assay Culture Agar into 10 ml. tubes of Bacto-Micro 

 Inoculum Broth and incubated for 24 hours at 37°C. The culture is then centri- 

 fuged, washed with sterile isotonic sodium chloride solution, and diluted before 

 use as inoculum. It is essential that the directions given in the discussion of 

 each assay medium be followed in minute detail, since the age, preparation and 

 size of the inoculum are most important factors in obtaining a satisfactory assay. 

 Although other media and methods may be used successfully for carrying the 

 cultures and preparing the inocula, we feel that uniformly good results will be 

 obtained if the methods described under each medium are followed. 



To rehydrate the medium, dissolve 37 grams of Bacto-Micro Inoculum Broth 

 in 1000 ml. distilled water. Distribute in 10 ml. quantities in tubes of 16-20 

 mm. diameter. Sterilize in the autoclave for 15 minutes at 15 pounds pressure 

 (121°C.). Final reaction of the medium will be pH 6.7. 



One hundred grams of Bacto-Micro Inoculum Broth will make 2.7 liters of 

 medium. 



