PEHYDRATED CULTURE MEDIA 35 



Broth Base, page 157; Bacto-Selenite Broth, page 158; Bacto-Brilliant Green 

 Agar, page 144. 



Endo Agar inoculated the same day as rehydrated may be used without auto- 

 clave sterilization. Under these conditions the medium need be heated only to 

 boiling to dissolve it completely before pouring into plates. 



To rehydrate the medium, suspend 41.5 grams of Bacto-Endo Agar in 1000 

 ml. of cold distilled water and heat to boiling to dissolve the medium completely. 

 Distribute in tubes or flasks and sterilize in the autoclave for 15 minutes at 15 

 pounds pressure (121°C.). The characteristic flocculant precipitate present in 

 the medium following autoclaving may be evenly dispersed by twirling or gently 

 shaking the flask just prior to pouring into sterile petri dishes. The final reaction 

 of the medium will be pH 7.5. 



One pound of Bacto-Endo Agar will make 10.9 liters of medium. 



» Standard Methods for the Examination ^ Blochem. Zeit., 96:133:1919. 



of Water and Sewage, 9th Edition: 195:1946. ^ MiHtary Surgeon, 57:280:1925. 



2 Standard Methods for the Examination ' Abst. Bact., 2:13:1918. 



of Dairy Products, gth Edition: 33:1948. 8 Standard Methods for the Examination 



8 Centr. Bakt., Abt. I, Orig., 35:109:1904. of Water and Sewage, 9th Edition: 187:1946. 

 * Stain Tech., 8:131:1933. 



BACTO 



LEVINE E.M.B. AGAR (B5) 



DEHYDRATED 



Bacto-Peptone 10 g. 



Bacto-Lactose 10 g. 



Dipotassium Phosphate 2 g. 



Bacto-Agar 15 g. 



Bacto-Eosin Y 0.4 g. 



Bacto-Methylenc Blue 0.065 g. 



Levine Eosin Methylene Blue Agar is recommended for the confirmation of 

 presumptive tests of members of the coliform group in the bacteriological exami- 

 nation of water, milk, and other dairy products according to "Standard Methods 

 for the Examination of Water and Sewage"^ and "Standard Methods for the 

 Examination of Dairy Products. "^ It may also be used for differential plate count 

 as mentioned in Appendix I of "Standard Methods for the Examination of Water 

 and Sewage."^ While pathogens concerned in enteric fevers caused by members 

 of the Salmonella and Shigella group will develop on this medium, forming 

 translucent, colorless colonies which are readily differentiated from lactose-fer- 

 menters, its principal function is to demonstrate the presence of coliform bacteria 

 from water and milk samples. 



Levine* developed an Eosin Methylene Blue Agar which gave excellent differ- 

 entiation of Escherichia coli and Aerobacter aerogenes. The colon colonies usually 

 show a dark center and have a greenish metallic sheen, but occasionally variants 

 have been observed similar to the type described but having no sheen. Another 

 variant grows effusely in colonies somewhat larger than the typical growth and 

 has a distinct metallic sheen. Colonies of A. aerogenes are usually much larger 

 than typical E. coli and tend to run together. The centers are usually brown in 

 color and not as dark as E. coli. The metallic sheen is only occasionally observed. 

 A more detailed differentiation is indicated in the accompanying table. 



To obtain the most satisfactory reactions, especially in the differentiation of 

 E. coli and A. aerogenes, it is very important that particular care be taken in the 

 choice of the dyes and a meticulous determination be made of their proper pro- 

 portions. The Bacto dyes in this medium are selected to satisfy the extreme 

 delicacy of the medium. Levine recommends that the reaction should not be 



