162 DIFCO MANUAL 



BACTO 



RUSSELL DOUBLE SUGAR AGAR (B84) 



DEHYDRATED 



Bacto-Beef Extract 1 g. 



Proteose Peptone No. 3, Difco . . 12 g. 



Bacto-Lactose 10 g. 



Bacto-Dextrose 1 g. 



Sodium Chloride 5 g. 



Bacto-Agar 15 g. 



Bacto-Phenol Red 0.025 g. 



Bacto-Russell Double Sugar Agar is widely employed in the primary identi- 

 fication of Gram-negative enteric pathogenic organisms, particularly the colon- 

 typhoid-salmonella-dysentery group. It distinguishes the dextrose-acid, dextrose- 

 gas, lactose-acid and lactose-gas forming organisms. Russell Double Sugar Agar 

 may be used to aid in the identification of pure cultures of colonies picked from 

 primary plating media such as MacConkey Agar, S S Agar, Bismuth Sulfite Agar 

 and others. 



Bacto-Russell Double Sugar Agar conforms to the original formula of Russell^ 

 except that phenol red replaces litmus, and Proteose Peptone No. 3 is utilized 

 in place of Bacto-Peptone. The phenol red indicator gives exceptionally clear- 

 cut brilliant reactions on both sides of the neutral point. Alkaline reactions turn 

 the indicator red, and acid reactions change it to yellow. Investigations have also 

 demonstrated that faster and clearer reactions are secured in the medium pre- 

 pared with Proteose Peptone No. 3. 



Russell Double Sugar Agar is used in tubes which are slanted so as to provide 

 a deep butt. Inoculation is made from isolated colonies or pure cultures by smear- 

 ing over the surface of the slant and stabbing the butt. After suitable incubation, 

 the production of acid under aerobic and under anaerobic conditions, on the slant 

 and in the butt, respectively, can be detected by changes in color of the indicator. 

 Gaseous fermentation is indicated by splitting of the agar or formation of bubbles 

 in the butt. 



Organisms capable of fermenting dextrose but not lactose, Salmonella typhosa 

 for example, will show an initial acid slant in short incubation periods. As the 

 dextrose is utilized, the reaction under aerobic conditions reverts and becomes 

 alkaline. Under anaerobic conditions, in the butt of the tube, these same organisms 

 are not capable of causing a reversion of the reaction, and remain acid. 



After 24-48 hours incubation a properly inoculated tube showing a red or 

 cerise slope and a yellow butt with or without gas formation indicates fermenta- 

 tion of the dextrose. Some strains of typhoid may require as long as 30-40 hours 

 to produce a characteristic alkaline slant. A tube showing a yellow slant and butt 

 with or without gas indicates fermentation of the lactose. A tube showing no 

 change indicates that neither dextrose nor lactose has been fermented. See the 

 table on page 161 for the reactions of various bacteria on Bacto-Russell Double 

 Sugar Agar and other differential tube media. 



To rehydrate the medium, suspend 44 grams of Bacto-Russell Double Sugar 

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

 medium completely. The solution is distributed in tubes which are stoppered 

 with cotton plugs or loosely fitting caps. Sterilize in the autoclave for 15 minutes 

 at 15 pounds pressure (121°C.). The tubes should be slanted so as to give a deep 

 butt when solid. The final reaction of the medium will be pH 7.4. 



One pound of Bacto-Russell Double Sugar Agar will make 10.3 liters of 

 medium. 

 ^ J. Med. Research, 25:217:1911. 



