DEHYDRATED CULTURE MEDIA 41 



To rehydrate the medium, dissolve 35.6 grams of Bacto-Lauryl Tryptose Broth 

 in 1000 ml. distilled water. Distribute into fermentation tubes and sterilize in the 

 autoclave for 15 minutes at 15 pounds pressure (121°C.). The final reaction of 

 the medium will be pH 6.8. 



One pound of Bacto-Lauryl Tryptose Broth is suiBcient for 12.7 liters single 

 strength medium. 



1 Am. J. Pub. Health, 31:127:1941. * J. Am. Water Works Assoc, 31:689:1939. 



2 Standard Methods for the Examination of ^ Am. J. Pub. Health, 31:351:1941. 

 Water and Sewage, gth Edition: 193:1946. « Am. J. Pub. Health, 33:ii99: i943- 



3 J. Am. Water Works Assoc, 30:979:1938. '^ Am. J. Pub. Health, 34:735:1944. 



SUPPLEMENTARY MEDIA 



for Water and Sewage Examination 



The media in this section are listed in Appendix I of "Standard Methods for 

 the Examination of Water and Sewage," Ninth Edition, 1946, or have been used 

 for a long period of time in the examination of water and sewage. 



In addition to the media discussed in detail in this section, other media 

 described elsewhere in the Manual are also used in Appendix I procedures. A 

 complete discussion of these media is given as indicated in the following listing. 



Brilliant Green Bile 2% 

 Formate Ricinoleate Broth 

 MacConkey Agar 

 Violet Red Bile Agar 

 Desoxycholate Lactose Agar 

 Levine E.M.B. Agar 



BACTO 



FUCHSIN LACTOSE BROTH (BIO) 



DEHYDRATED 



Bacto-Beef Extract 3 g. 



Bacto-Peptone 5 g. 



Bacto-Lactose 5 g. 



Bacto-Basic Fuchsin 0.015 g. 



Bacto-Fuchsin Lactose Broth is a selective medium which may be used in 

 parallel planting with Lactose Broth in the control of water filtration plant oper- 

 ation as described in Appendix I of "Standard Methods for the Examination of 

 Water and Sewage"^. 



As a result of investigations of media to reduce the number of false positives 

 occurring in examination of waters for Escherichia coli, Ritter^ devised a medium 

 composed of Lactose Broth with the addition of basic fuchsin. The dye is present 

 in the medium in a concentration which has been found to inhibit satisfactorily 

 Gram-positive organisms and other bacteria which may be responsible for false 

 positive tests for E. coli. McCrady,^ in his study on procedures for the detection 

 of the presence of coliform organisms in water, found that Fuchsin Lactose Broth, 

 although satisfactory for some waters as a direct presumptive medium, could not 

 be used as satisfactorily as Lactose Broth with all waters, and, therefore, recom- 



