48 DIFGOMANUAL 



facilitated the fermentation of dextrose by members of Streptococcus Group D 

 and Hajna^ described the addition of glycerol to SF Medium to give the same 

 rapid acid production with pure cultures of S. fecalis as with stool specimens. 

 The concentration of Brom Cresol Purple was decreased to detect more readily 

 the color change from purple to yellow within 24 hours incubation. 



Hajna^ reported that growth with acid production is almost definite evidence 

 of the presence of fecal streptococci. Streptococcus zymogenes, durans and lique- 

 faciens develop at 37°C. or 45°G. Streptococcus lactis does not grow at 45°G. 

 making possible a differentiation of these organisms using this incubation tempera- 

 ture. An incubation temperature of 37°G. is suggested for the detection of fecal 

 streptococci from swimming pools, water samples, food products such as oysters 

 and crab meat and from pathological material such as catheterized urine and 

 exudates. 



To rehydrate the medium, dissolve 36 grams Bacto-B A G G Broth in 1000 ml. 

 of distilled water containing 5 ml. Bacto-Glycerol. Distribute in tubes in 10 ml. 

 amounts and sterilize in the autoclave for 15 minutes at 10 pounds pressure 

 (116°G.). Sterilization at 121 °G. is not recommended. Final reaction of the 

 medium will be pH 6.9. 



When the inoculum is larger than 1 ml., particular care must be taken to pre- 

 serve the correct concentration of the ingredients after dilution with the sample. 

 For example, 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-B A G G Broth will make 12.6 liters of medium. 



iPub. Health Lab., 9:80:1951. a Am. J. Pub. Health, 33:550:t943. 



BACTO 



AZIDE DEXTROSE BROTH (B387) 



DEHYDRATED 



Bacto-Beef Extract 4.5 g. 



Bacto-Tryptone 15 g. 



Bacto-Dextrose 7.5 g. 



Sodium Chloride 7.5 g. 



Sodium Azide 0.2 g. 



Bacto-Azlde Dextrose Broth is a liquid medium selective for streptococci, and 

 is recommended for use in the detection of these organisms from milk, water, 

 swimming pools, sewage, feces and other specimens. This medium is prepared 

 according to a formula given by Rothe^ as emanating from the laboratory of 

 the Illinois State Health Department. 



The use of sodium azide as an inhibitor of Gram-negative organisms in an 

 attempt to detect streptococci has been pointed out by a number of investigators. 

 Edwards^ in 1933 used a liquid medium containing crystal violet and sodium 

 azide as a selective broth in the isolation of mastitis streptococci. Hartman^ 

 reported the value of sodium azide as a selective agent for the isolation of 

 streptococci causing mastitis. Bryan, Devereux, Hirschey and Gorbett* reported 

 that sodium azide in a concentration of 1 :5000 was a better selective preservative 

 for milk cultures and gave more accurate results for the microscopic and Hotis 

 tests for Streptococcus mastitis than 1 : 50,000 brilliant green. 



Mallmann, Botwright and Ghurchill^ in studying the selective bacteriostatic 

 effect of slow oxidizing agents reported that sodium azide exerted a bacterio- 

 static effect on Gram-negative bacteria and permitted the growth of Gram- 

 positive organisms. Hajna and Perry ^ used this principle in designing a selective 



