DEHYDRATED CULTURE MEDIA 49 



medium for the detection of fecal streptococci. Their medium, Bacto-S F 

 Medium, is described in detail on page 46 of the Manual. Ritter and Treece^ 

 also used 0.02 per cent sodium azide in a broth containing 2 per cent Proteose 

 Peptone No. 3, 0.1 per cent dextrose and 0.5 per cent sodium chloride for the 

 detection of cocci in swimming pools. The selectivity of this medium was later 

 increased by the addition of crystal violet to this medium by Ritter.^ 



In a comparative study of media for the detection of streptococci in water 

 and sewage Mallmann and Seligmann^ used Bacto-Azide Dextrose Broth. They 

 reported the medium offered a new means of measuring the presence of strepto- 

 cocci in water, sewage, shellfish and other materials in which sewage pollution 

 is suspected. 



To rehydrate the medium dissolve 34.7 grams Bacto-Azide Dextrose Broth in 

 1000 ml. distilled water. Distribute in tubes and sterilize in the autoclave for 15 

 minutes at 15 pounds pressure (121°C.). Inocula of 1 loop or 1 ml. may be 

 added to 10 ml. or more of medium. The medium should be prepared in mul- 

 tiple strength for larger inocula to preserve the correct concentration of in- 

 gredients. For example, if 10 ml. of inoculum is to be added to 10 ml. of me- 

 dium, the medium should be prepared in double strength. Final reaction of the 

 medium will be pH 7.2. 



One pound of Bacto-Azide Dextrose Broth will make 13.1 liters single 

 strength medium. 



^ Rothe, Personal Communication, 1948. ^ Am. J. Pub. Health, 33:550:1943. 



2 J. Comp. Path. Therap., 46:211:1c " ' ' '^ 



8 Milchw. Forsch., 18:116:1936. 



* North Am. Vet., 20:424:1939. 



6 J. Infectious Diseases, 69:215:1941. 



2 J. Comp. Path. Therap., 46:211:1933. "Am. J. Pub. Health, 38:1532: 



8 Milchw. Forsch., 18:116:1936. ^Ritter, Personal Communication, 1949. 



* North Am. Vet., 20:424:1939. » Am. J. Pub. Health, 40:286:1950. 



BACTO 



BORIC ACID BROTH (B439) 



DEHYDRATED 



Proteose Peptone, Difco 10 g. 



Bacto-Lactose 5 g. 



Dipotassium Phosphate 12.2 g. 



Monopotassium Phosphate 4.1 g. 



Boric Acid 3.25 g. 



Bacto-Boric Acid Broth is a liquid medium for the enrichment and presump- 

 tive identification of Escherichia coli from water and food, as indicated by 

 growth and gas production at 42.5°^3.5°C. This medium is prepared accord- 

 ing to the formula of Vaughn, Levine and Smith.^ 



The presence of E. coli is considered by many to be a reliable index of 

 human or animal fecal contamination, and for some food products the presence 

 of coliform bacteria may not be a true indication of the sanitary quality 

 of the food. Thus a method which would permit the selective enrichment and 

 identification of E. coli would be of decided value in the determination of the 

 sanitary significance of the various coliform bacteria found in foods. Many 

 methods have been devised for this purpose. Bacto-E G Medium as described 

 on page 45 is a modification of the Eijkman test designed to detect E, coli at an 

 incubation temperature of 45.5 °C. Boric acid has been added to lactose media to 

 favor the growth of E. coli as described by Levine^.* and Levine, Epstein and 

 Vaughn.3 Bartram and Black^ and Wolford and Berry^ reported boric acid to 

 be of value in the detection and differentiation of E. coli from other coliform 

 bacteria. Vaughn, Levine and Smith^ made a study of the various ingredients, 



