134 DIFGO MANUAL 



the medium need be heated only to boiling to dissolve it completely before pour- 

 ing into petri plates. 



Sterilization reduces the methylene blue, leaving the medium orange color. 

 The normal purple color of the medium may be restored by gentle shaking. If 

 the reduced medium is not shaken to oxidize the methylene blue, a dark zone 

 beginning at the top and extending downward through the medium will gradu- 

 ally make its appearance. The sterilized medium normally contains a flocculant 

 precipitate which should not be removed. By cooling to 50° C. and gently agitat- 

 ing the medium before pouring it into plates, this flocculation will be finely dis- 

 persed, giving a medium without any objectionable precipitate. 



One pound of Bacto-E.M.B. Agar will make 12.6 liters of medium. 



* J, Infectious Diseases, 18:596:1916. 2 j, infectious Diseases, 23:43:1918. 



BACTO 



LEVINE E.M.B. AGAR 



DEHYDRATED 



Levine E.M.B. Agar has been used for the isolation of enteric pathogens. A 

 complete discussion of Bacto-Levine E.M.B. Agar is given on page 35. 



BACTO 



ENDO AGAR 



DEHYDRATED 



Endo Agar has been used rather extensively in the past for the isolation of 

 enteric pathogens. A complete discussion of Bacto-Endo Agar is given on page 34. 



BACTO 



S S AGAR (B74) 



DEHYDRATED 



Bacto-Beef Extract 5 g. 



Proteose Peptone, Difco 5 g 



Bacto-Lactose 10 g, 



Bacto-Bile Salts No. 3 8.5 g 



Sodium Citrate 8.5 g 



Sodium Thiosulfate 8.5 g 



Ferric Citrate 1 g 



Bacto-Agar 13.5 g. 



Bacto-Brilliant Green 0.00033 g 



Bacto-Neutral Red 0.025 g 



Bacto-S S Agar is a highly selective medium recommended for the isolation of 

 Shigella and Salmonella from stools and other materials suspected of containing 

 these organisms. Bacto-S S Agar was devised to provide excellent differentiation 

 of lactose fermenters from lactose non-fermenters, and to give maximum inhibi- 

 tion of coliform organisms without restriction of the growth of pathogenic Gram- 

 negative bacilli occurring in specimens. Inasmuch as Bacto-S S Agar is a selective 

 medium, we recommend that a non-selective medium such as Bacto-MacConkey 

 Agar be used in conjunction with it. To insure the highest percentage of positive 

 isolations of all intestinal pathogens, we further recommend the use of Bacto- 



