DEHYDRATED CULTURE MEDIA 163 



BACTO 



SACCHAROSE MANNITOL AGAR (B87) 



DEHYDRATED 



Bacto-Beef Extract 1 g. 



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



Saccharose, Difco 10 g. 



^-Mannitol, Difco 1 g. 



Bacto-Agar 15 g. 



Bacto-Phenol Red 0.03 g. 



Bacto-Saccharose Mannitol Agar is a tube medium employed in the differenti- 

 ation of pure cultures of Gram-negative intestinal bacteria. This medium permits 

 the determination of the formation of acid and gas from saccharose and mannitol. 

 It is employed 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. 



Russell^ made a noteworthy contribution toward the identification of the 

 Gram-negative intestinal bacterial rods by the introduction of his Dextrose Lac- 

 tose Agar. Kendall and Ryan^ introduced a new agar medium containing sac- 

 charose and mannitol, two important sugars in the differentiation and identifica- 

 tion of members of the intestinal group. Their Saccharose Mannitol Agar is used 

 in the same manner as Russell's and, when employed in conjunction with it, per- 

 mits observations of the fermentation reactions of the bacteria on four sugars by 

 using only two media. 



Bacto-Saccharose Mannitol Agar duplicates the original formula of Kendall 

 and Ryan except that phenol red has replaced Andrade indicator. The phenol 

 red indicator responds rapidly to slight changes in reaction due to growth of 

 inoculated organisms. The tubes are inoculated with pure cultures by smearing 

 the surface of the slant and stabbing into the butt. On this medium cultural 

 reactions are clear-cut and readings may be made after 18-24 hours incubation 

 at 37°G. A red slant and yellov/ butt, with or without gas formation, indicates 

 fermentation of the mannitol. A yellow slant and butt, with or without gas, indi- 

 cates that either saccharose alone or both sugars have been fermented. A tube 

 remaining unchanged, or becoming cerise, indicates that neither sugar has been 

 attacked. For a table showing typical cultural reactions on this and other differ- 

 ential tube media, see page 161. 



To rehydrate the medium, suspend 39 grams of Bacto-Saccharose Mannitol 

 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.). Allow the tubes to solidify in a slanting position 

 to provide a generous butt. The final reaction of the medium will be pH 7.5. 



One pound of Bacto-Saccharose Mannitol Agar will make 11.6 liters of 

 medium. 



"•J. Med. Research, 25:217:1911. " ]. Infectious Diseases, 24:400:1919. 



