44 DIFCOMANUAL 



One pound of Bacto-Crystal Violet Lactose Broth will make 28.3 liters of 

 medium. 



1 Standard Methods for the Examination * Standard Methods for the Examination 



of Water and Sewage, gth Edition: 226:1946. of Water and Sewage, gth Edition: 195:1946. 



*J. Bact., 20:381:1930. 5 Standard Methods for the Examination 



* Am. J. rub. Health, 27:1243:1937. of Water and Sewage, 8th Edition: 203:1936. 



BACTO 



EIJKMAN LACTOSE MEDIUM (B17) 



DEHYDRATED 



Bacto-Tryptose 15 g. 



Bacto-Lactose 3 g. 



Dipotassium Phosphate 4 g. 



Monopotassium Phosphate 1.5 g. 



Sodium Chloride 5 g. 



Bacto-Eijkman Lactose Medium is used in the differentiation of Escherichia 

 coli from other coliform bacteria. This medium may also be used in parallel 

 planting with Lactose Broth in the control of water filtration plant operations. 

 Its use is suggested in Appendix I of the Ninth Edition of "Standard Methods for 

 the Examination of Water and Sewage"^ for this purpose. 



In 1904 Eijkman^ described a method of separating the strains of coli originat- 

 ing from the feces of warm-blooded animals from the strains characteristic of 

 cold-blooded animals. His method consisted essentially in placing the water under 

 investigation in fermentation tubes or flasks and adding one-eighth its volume of 

 a sterile solution containing 10 per cent dextrose, 10 per cent peptone, and 5 per 

 cent sodium chloride. This mixture was then incubated at 46° C. The presence 

 of a uniform turbidity and gas production was considered indicative of the pres- 

 ence of fecal colon strains. Many investigators have studied this method with 

 water samples and pure cultures with varying results. One of the factors limiting 

 the value of this method was the inability to obtain growth of transplants from 

 positive tubes incubated at 46° G. Undoubtedly, the acidity at the relatively high 

 temperature of incubation was responsible for the death of the culture within 24 

 to 48 hours. 



Perry and Hajna^ modified Eijkman's original method of decreasing the carbo- 

 hydrate content and adding a phosphate buffer. Their study demonstrated that 

 with 0.3 per cent dextrose and a potassium phosphate buffer the reaction of the 

 medium, after inoculation with E. coli and incubation, was pH 5.6, while under 

 the conditions described by Eijkman the reaction of the medium was pH 4.5. 

 As a result, they were able to culture E. coli in every instance after incubation 

 at 46° C. for 96 hours and for longer periods. 



Perry* in 1939 reported on the use of a modified Eijkman Medium using 0.3 

 per cent lactose. This medium had been used successfully and routinely for the 

 isolation of E. coli for a number of years. In a personal communication, Dr. 

 Perry° recommended that Bacto-Tryptose replace Bacto-Peptone in this formula. 

 The specificity of this medium for the detection of E. coli of fecal origin requires 

 that the composition of the medium be uniform and exact, and that the incuba- 

 tion temperature be properly controlled at 45.5 to 46° G. at all times. The formula 

 for Bacto-Eijkman Lactose Medium conforms to the formula for Eijkman Broth 

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

 and Sewage."^ 



To rehydrate the medium, dissolve 28.5 grams of Bacto-Eijkman Lactose 

 Medium in 1000 ml. of distilled water and dispense in fermentation tubes. Steri- 



