166 DIFGO MANUAL 



that the suspicious colony be purified by streaking on MacConkey Agar before 

 inoculating into Kligler Iron Agar. This procedure is always recommended to 

 insure culture purity when picking from poured plates of Bismuth Sulfite Agar. 

 It is often possible to detect contaminated cultures on Kligler Iron Agar slants, 

 and when this is the case it is necessary to isolate the organism in pure culture 

 before its typical cultural reaction can be determined. 



Organisms capable of fermenting dextrose but not lactose, S. typhosa for exam- 

 ple, 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. 



The fermentation reactions in Kligler Iron Agar are similar to those in Russell 

 Double Sugar Agar, i.e., a red slant and yellow butt with or without gas indicates 

 fermentation of the small quantity of dextrose, a yellow slant and butt with or 

 without gas formation indicates fermentation of the lactose, while a tube showing 

 no change indicates that neither dextrose nor lactose has been attacked. In addi- 

 tion to these fermentation reactions, Kligler Iron Agar indicates whether or not 

 hydrogen sulfide is produced. This is shown by a blackening of the medium. 

 Freshly prepared media will give the best reactions. For characteristic reactions 

 of some of the enteric organisms on this medium see the table on page 161. 



To rehydrate the medium, suspend 55 grams of Bacto-Kligler Iron Agar in 

 1000 ml. of cold distilled water and heat to boiling to dissolve the medium com- 

 pletely. The solution is distributed in tubes which are stoppered with cotton plugs 

 or loosely fitting caps. Sterilize by autoclaving for 15 minutes at 15 pounds pres- 

 sure (121°C.). The reaction of the medium after sterilization v/ill be pH 7.4. 

 Allow the tubes to solidify in a slanting position in a manner which will give a 

 generous butt. Best reactions are obtained on freshly prepared media. 



One pound of Bacto-Kligler Iron Agar will make 8.2 liters of medium. 



-^Am. J. Pub. Health, 7:1042:1917. 3 j. Bact., 13:183:1927- 



a J. Exp. Med., 28:319:1918. 4 J. Lab. Clin. Med., 25:649:1940. 



BACTO 



TRIPLE SUGAR IRON AGAR (B265) 



DEHYDRATED 



Bacto-Beef Extract 3 g. 



Bacto- Yeast Extract 3 g. 



Bacto-Peptone 15 g. 



Proteose Peptone, Difco 5 g. 



Bacto-Lactose 10 g. 



Saccharose, Difco 10 g. 



Bacto-Dextrose 1 g. 



Ferrous Sulfate 0.2 g. 



Sodium Chloride 5 g. 



Sodium Thiosulfate 0.3 g. 



Bacto-Agar 12 g. 



Bacto-Phenol Red 0.024 g. 



Bacto-Triple Sugar Iron Agar is recommended as a medium for use in the 

 identification of Gram-negative enteric pathogens in the routine examination of 

 stools. It is of especial value when used in conjunction with MacConkey Agar, 

 S S Agar, Bismuth Sulfite Agar, Brilliant Green Agar, E.M.B. Agar and Endo 

 Agar. This medium indicates the ability of an organism to ferment lactose, sac- 

 charose and dextrose with formation of acid and gas, and also its ability to pro- 

 duce hydrogen sulfide. These characteristics are employed in most schema for 

 identifying members of the Salmonella-S higella groups. 



