DEHYDRATED CULTURE MEDIA 43 



in 1000 ml. of distilled water. Dispense into fermentation tubes in 10 ml. quanti- 

 ties. Sterilize in the autoclave for 15 minutes at 15 pounds pressure (121°C.). 

 The final reaction of the medium will be pH 6.9. 



For water filtration plant control work or other procedures where the inocu- 

 lum is greater than a loop or 1 ml., particular care must be taken to preserve the 

 correct concentration of the ingredients after dilution with the sample. For ex- 

 ample, if 10 ml. of water are to be added to 10 ml. of medium, the medium 

 should be prepared in double strength. 



One pound of Bacto-M.B.-B.C.P. Medium will make 23.1 liters of medium. 



1 Standard Methods for the Examination ^ Standard Methods for the Examination 



of Water and Sewaee, gth Edition: 226:1946. of Water and Sewage, 8th Edition: 261:1936. 



a J. Am. Water Works Assoc, 21:1067:1929. * J. Bact., 37:37' :i939- 



BACTO 



CRYSTAL VIOLET LACTOSE BROTH (B8) 



DEHYDRATED 



Bacto-Peptone 5 g. 



Bacto-Lactose 5 g. 



Dipotassium Phosphate 5 g. 



Monopotassium Phosphate 1 g. 



Bacto-Crystal Violet 0.00143 g. 



Bacto-Crystal Violet Lactose Broth is a selective medium used in parallel plant- 

 ing with Lactose Broth in the control of water filtration plant operations as de- 

 scribed in Appendix I of "Standard Methods for the Examination of Water and 

 Sewage"^ It is prepared according to the formula suggested by Salle.^ 



Crystal Violet Lactose Broth is a buffered Lactose Broth containing crystal 

 violet (gentian violet) in a concentration sufficient to inhibit Gram-positive or- 

 ganisms and other bacteria which may be responsible for false positive tests. The 

 concentration of this bacteriostatic agent in the medium is not sufficient to affect 

 the growth of members of the coliform group. Salle^ suggested that such a me- 

 dium be employed in the bacteriological examination of water, and McCrady^ in 

 studies on media for the detection of the presence of coliform organisms in water, 

 found that while selective media were not as satisfactory as Lactose Broth for 

 the presumptive test, they could be recommended for confirmation of the pre- 

 sumptive test, and that for this purpose Crystal Violet Lactose Broth could be 

 recommended. 



The Ninth Edition of "Standard Methods"* permits the use of Crystal Violet 

 Lactose Broth as an alternate medium for the confirmed test for the presence 

 of members of the coliform group when it has been shown to yield a maximum 

 number of coliform organisms as indicated by a series of completed tests. Bacto- 

 Crystal Violet Lactose Broth is prepared according to the formula specified in 

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

 1936 our label has carried a statement to that effect. 



To rehydrate the medium, dissolve 16 grams of Bacto-Crystal Violet Lactose 

 Broth in 1000 ml. of distilled water. The medium is distributed in fermentation 

 tubes and sterilized by autoclaving for 15 minutes at 15 pounds pressure. 

 (121°C.). The final reaction of the medium will be pH 7.4. 



For water filtration plant control work, where the inoculum is greater than 1 

 ml., particular care must be taken to preserve the correct concentrations of the 

 ingredients after dilution with the sample. For example, if 10 ml. of water arc 

 to be added to 10 ml. of medium, the medium should be prepared in double 

 strength. 



