EXAMINATION OF WATER AND SEWAGE 149 



SECTION 4 



DETERMINATION OF ANAEROBES IN SEWAGE 



1. Prepare dilutions of sewage, 1:100, 1:1,000, 

 and 1 : 10,000. 



2. Inoculate a series of 10 litmus milk tubes for 

 each dilution with i c.c. of each dilution. 



3. Heat these tubes in a water bath at 80° C. for 

 15 minutes. 



4. Incubate at 37° C. for 48 hours, in an anaerobic 

 jar (see p. 137). 



5. Determine the number of anaerobes present. 

 NoTE.^-Heating the tubes at 80° C. kills all vegetative forms 



of bacteria, leaving only the spores alive. These develop the 

 thermostat and their presence is recognized by violent gas forma- 

 tion and breaking-up of the milk curd. The number of anaerobes 

 is determined by the same formula as the -number of B. coli, sub- 

 stituting the number of milk tubes showing growth of anaerobes 

 for the letter N in the formula. 



SECTION s 



STUDY OF B. COLI AND STREPTOCOCCI 



Isolate colonies of B. coli and Streptococcus by plat- 

 ing from the fermentation tubes in lactose litmus agar. 

 Carry the two organisms through all the media and 

 determine whether their characteristics are typical 

 according to the rules laid down in the Committee 

 Report of the American Public Health Association. 

 If they are not typical, they must be rejuvenated 

 according to Fuller and Johnson's method. This 



