30 DIFGOMANUAL 



variety of materials may be added, for the preparation of a large number of dif- 

 ferential, selective, and enriched media requiring only the addition of dyes, salts, 

 carbohydrates, tissues, or serous fluids. An enriched medium such as Rosenow* 

 described for the isolation of streptococci from infected teeth, was prepared by 

 adding dextrose, pieces of sterile brain tissue, and marble chips to Nutrient Broth. 



Bouillon or Beef Broth as suggested by LoefRer was one of the earliest media 

 used in bacteriology. An infusion of meat and a peptone constituted the nutri- 

 ments of this medium. Later it was shown that for many routine purposes beef 

 extract could satisfactorily replace the infusion of fresh meat and had the decided 

 advantage of ease of preparation, uniformity, and economy. The American Public 

 Health Association recognized the advantage of beef extract in standard culture 

 media and in 1917 discontinued the use of infusion of beef in standard media. 

 Bacto-Nutrient Broth has been prepared to duplicate the formula approved by 

 the American Public Health Association and since 1927 our label has carried a 

 statement to this effect. 



Bacto-Nutrient Broth is recommended for use in the tube dilution method of 

 testing the sensitivity of microorganisms to antibiotics. Waisbren, Carr and 

 Dunnett* showed that Bacto-Nutrient Broth, Bacto-Dextrose Broth or Bacto- 

 Tryptose Phosphate Broth were suitable media for comparative sensitivity test 

 studies while a Tryptic soy medium inhibited the action of Neomycin, Aureo 

 mycin, Terramycin and Polymyxin against the test organism. 



To rehydrate the medium, dissolve 8 grams of Bacto-Nutrient Broth in 1000 

 ml. of distilled water. Distribute in 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-Nutrient Broth will make 56.7 liters of medium. 



^Standard Methods for the Examination ^ J. Dental Research, 1:205:1919. 



of Water and Sewage, 9th Edition: 185:1946. ^ Am. J. Clin. Path., 21:884:1951. 

 3 Standard Methods for the Examination 



of Dairy Products, 9th Edition: 166:1948. 



BACTO 



LACTOSE BROTH (B4) 



DEHYDRATED 



Bacto-Beef Extract 3 g. 



Bacto-Peptone 5 g. 



Bacto-Lactose 5 g. 



Bacto-Lactose Broth is recommended for use in the presumptive test for mem- 

 bers of the coliform {Escherichia- Aerobacter) group from water and other ma- 

 terials. This medium is prepared according to the formula specified in "Standard 

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

 for the Examination of Dairy Products."^ 



In the determination of the potability of drinking water one of the most im- 

 portant tests is the detection of possible fecal contamination. The presence of 

 Escherichia coli is generally considered to be an indication of fecal pollution of 

 the water. 



The demonstration of the presence of coliform bacteria in water has been re- 

 duced to a relatively simple process as outlined in "Standard Methods." Since 

 1917 the recommended procedure has been: 



1. The determination of gas production in Lactose Broth resulting from the 

 direct inoculation of water (presumptive test). 



2. The inoculation of differential or selective media from tubes of fermented 

 Lactose Broth (confirmed test),. 



