DEHYDRATED CULTURE MEDIA 139 



For the routine examination of stool and urine specimens it is recommended 

 that Bacto-MacConkey Agar, a non-selective medium, and Bacto-Bismuth Sulfite 

 Agar or Bacto-S S Agar be run in conjunction with Bacto-Desoxycholate Citrate 

 Agar. 



Saccharose in 1 per cent concentration may be added to isolation media, such 

 as Bacto-Desoxycholate Citrate Agar to permit the detection of certain members 

 of the coliform group which ferment saccharose more readily than lactose. This 

 principle was described by Holt-Harris and Teague^ and has been employed by 

 many other bacteriologists. In some laboratories, pathogenic significance is 

 assigned to these organisms, and under such conditions, saccharose should not be 

 added to the medium. 



To rehydrate the medium, suspend 70 grams of Bacto-Desoxycholate Citrate 

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

 completely. Do not sterilize the medium in the autoclave. Pour the medium into 

 petri dishes and allow the surface to dry for two hours with the covers partially 

 removed before inoculation. The final reaction of the medium will be pH 7.5. 



One pound of Bacto-Desoxycholate Citrate Agar will make 6.5 liters of 

 medium. 



1 J. Path. Bact., 40:581:1935- Edition: 212: 1950. „ ^ c 



2 Diagnostic Procedures and Reagents, 3rd ^ j. Infectious Diseases, 18:596:1916. 



BACTO 



BISMUTH SULFITE AGAR (B73) 



DEHYDRATED 



Bacto-Beef Extract 5 g. 



Bacto-Peptone 10 g. 



Bacto-Dextrose 5 g. 



Disodium Phosphate 4 g. 



Ferrous Sulfate 0.3 g. 



Bismuth Sulfite Indicator 8 g. 



Bacto-Agar 20 g. 



Bacto-Brilliant Green 0.025 g. 



Bacto-Bismuth Sulfite Agar, a modification of the Wilson and Blair formula, 

 is a highly selective medium designed especially for the isolation of Salmonella 

 typhosa from feces, urine, sewage and other materials harboring this organism. 

 It is of special value in detecting typhoid carriers and in checking cases before 

 release. It is also satisfactory for the isolation of other members of the Salmonella 

 group, particularly after preliminary enrichment in Tetrathionate Broth. The use 

 of Bismuth Sulfite Agar is specified in "Standard Methods for the Examination 

 of Dairy Products"^ for the isolation of pathogenic bacteria from cheese, and in 

 "Diagnostic Procedures and Reagents"^ of the American Public Health Associa- 

 tion for the examination of specimens for evidence of infection with Salmonella 

 and Shigella. 



The early history of the development of Bismuth Sulfite Agar may be found 

 in the reports of Wilson, ^-^ and Wilson and Blair^'^''^ who clearly demonstrated 

 the superiority of this type of medium over other media in the isolation of ty- 

 phoid. The unusually interesting claims of the proponents, and the many enthu- 

 siastic reports of its successful use by other investigators, stimulated us in an 

 endeavor to prepare this medium in the dehydrated form. The result of this in- 

 vestigation was Bacto-Bismuth Sulfite Agar. 



Bacto-Bismuth Sulfite Agar closely approaches the ideal medium for the isola- 

 tion of S, typhosa from feces, urine, sewage and other infectious materials. Upon 



