INGREDIENTS OF CULTURE MEDIA 287 



Bacto-Bile Salts has proven particularly valuable in the preparation of Bacto- 

 Tetrathionate Broth. This medium is discussed on page 157. 



Bacto-Bile Salts is readily soluble in distilled water and is neutral in reaction. 

 It may, therefore, be used in preparing media without adjustment of reaction 

 or filtration. 

 ij. Hyg., 5:333:1905. 



BACTO-BILE SALTS NO. 3 (B130) 



Bacto-Bile Salts No. 3 is a modification of Bacto-Bile Salts and is prepared 

 especially for use in Bacto-MacConkey Agar, Bacto-S S Agar and Bacto- Violet 

 Red Bile Agar. In our investigations on these media we found that the Bacto-Bile 

 Salts gave a somewhat heavy precipitate around lactose fermenting colonies, 

 which, under certain conditions, made it difficult to detect colonies of the patho- 

 genic lactose non-fermenters. Bacto-Bile Salts No. 3 obviates this fault, giving a 

 clearer medium and also reducing the precipitation around the coliform colonies, 

 thus facilitating the detection of lactose non-fermenting colonies. A complete 

 discussion of these media, using Bacto-Bile Salts No. 3, is given on pages 131, 134, 

 and 61, respectively. 



Bacto-Bile Salts No. 3 is readily soluble in distilled water and is neutral in 

 reaction. It may, therefore, be used in preparing media without adjustment of 

 reaction or filtration. 



SODIUM TAUROGHOLATE, DIFGO (B278) 



Sodium Taurocholate, Difco is the sodium salt of a conjugated bile acid used 

 generally in bacteriological culture media for the isolation and cultivation of 

 members of the enteric group. Like whole bile, it has the cultural characteristic 

 of inhibiting the growth of Gram-positive organisms and spore forming bacteria, 

 without inhibiting the development of Gram-negative bacilli. 



Sodium Taurocholate, Difco contains about 75 per cent sodium taurocholate 

 along with other naturally occurring salts of bile acids. It is readily soluble in 

 distilled v/ater forming a clear amber solution, neutral in reaction. 



SODIUM DESOXYGHOLATE, DIFGO (B248) 



Sodium Desoxycholate, Difco is the sodium salt of desoxycholic acid. It is 

 used in bacteriological culture media and in the pneumococcus bile solubility 

 test. Sodium desoxycholate is readily soluble in distilled water, giving a clear 

 colorless solution neutral in reaction. 



Sodium desoxycholate, like bile and other bile salts when used in bacterio- 

 logical culture media, is inhibitive to Gram-positive cocci and spore forming 

 organisms but is not inhibitory to Gram-negative enteric bacilli. Since sodium 

 desoxycholate is a salt of a highly purified bile acid it is used in culture media in 

 lower concentrations than is naturally occurring bile. 



Leifson^ described media for the enumeration of coliform organisms from 

 milk, water, sewage, etc., and for the isolation of enteric pathogens using sodium 

 desoxycholate to inhibit Gram-positive organisms. He also prepared a selective 

 medium using sodium desoxycholate and sodium citrate for the isolation of 

 intestinal pathogens. Coliform as well as Gram-positive organisms are inhibited 

 on this Desoxycholate Citrate Agar. Bacto-Desoxycholate Agar and Bacto-Desoxy- 

 cholate Citrate Agar, prepared with sodium desoxycholate, are discussed on pages 

 63 and 138, respectively. 



Sodium desoxycholate is also used in 10 per cent concentration in the bile 

 solubility test for pneumococci. 



1 J. Path. Bact., 40:581:1935. 



