INGREDIENTS OF CULTURE MEDIA 295 



B AGTO-THIONIN ( B 1 96 ) 



Bacto-Thionin (CI. No. 920) is recommended for use in preparing the 

 thionin medium employed in the differentiation of Brucella types. In Tryptose 

 Agar, as discussed on page 111, Bacto-Thionin may be used for the differentiation 

 of Brucella in a concentration of 1 : 200,000. Upon Thionin Tryptose Agar 

 Brucella melitensis and B. suis grow readily while B. abortus fails to develop. 



SULFONPHTHALEIN AND OTHER INDICATORS 



In selecting this group of indicators^-- we have chosen those generally employed 

 in most laboratories. The use of these indicators in the preliminary adjustment 

 of culture media reactions, or as indicators of bacterial metabolism in the media 

 themselves, is well-known and needs no further explanation. These indicators 

 have been subjected to both bacteriological and chemical assay. They are non- 

 toxic in the concentration usually employed in media, and indicate color changes 

 at various reactions as shown below. 



* Clark: The Determination of Hydrogen Ions, => Pharmacopeia of the United States, XIV 1970: 

 1928. 1950. 



Indicators Showing Preparation, pH Ranges and Color Changes 



pH Color 



A* Range pK Acid Alkali 



Bacto-Cresol Red (acid) (B204) 26.2 0.2-1.8 — Red- Yellow 



( o-Gresolsulfonphthalein ) 

 Bacto-Meta Cresol Purple (acid) (B205) . . 26.2 1.2-2.8 1.51 Red-Yellow 



( m-Cresolsulf onphthalein ) 

 Bacto-Thymol Blue (acid) (B202) 21.5 1.2-2.8 1.5 Red-Yellow 



( Thymolsulfonphthalein ) 

 Bacto-Brom Phenol Blue (B199) 14.9 3.0-4.9 3.98 Yellow-Blue 



( Tetrabromophenolsulf onphthalein ) 

 Bacto-Brom Cresol Green (B200) . 14.3 3.8-5.4 4.67 Yellow-Blue 



(Tetrabromo-o-cresolsulf onphthalein) 

 Bacto-Brom Cresol Purple (B201) 18.5 5.2-6.8 6.3 Yellow-Purple 



( Dibromo-o-cresolsulf onphthalein ) 

 Bacto-Brom Thymol Blue (B202) 16.0 6.0-7.6 7.0 Yellow-Blue 



( Dibromo thymolsulfonphthalein ) 

 Bacto-Phenol Red (B203) 28.2 6.8-8.4 7.9 Yellow-Red 



( Phenolsulf onphthalein ) 

 Bacto-Cresol Red (alkaline) (B204) 26.2 7.2-8.8 8.3 Yellow-Red 



( o-Cresolsulf onphthalein ) 

 Bacto-Meta Cresol Purple (alkaline) (B205) 26.2 7.4-9.0 8.32 Yellow-Purple 



( m-Cresolsulfonphthalein ) 

 Bacto-Thymol Blue (alkaline) (B206) .... 21.5 8.0-9.6 8.9 Yellow-Blue 



(Thymolsulfonphthalein ) 



♦A — ml. 0.0 IN NaOH required per 0.1 g. indicator. Dilute to 250 ml. with distilled 

 water for 0.04 per cent solution for use as indicator for colorimetric pH determi- 

 nations. 



