428 BACTERIOLOGICAL ANALYSES 



Aluminum spreader. 



Tubes of various media, including carbohydrate media. 



Agglutinating sera, etc. 



METHOD. 



1. Number a set of bile salt broth tubes 1-5, and 

 a duplicate set ia-5a. 



2. Number one flask 7 and another 8. 



3. To Tubes No. i and la add o.i c.c. water sample. 

 To Tubes No. 2 and 2 a add 'i c.c. water sample. 

 To Tubes No. 3 and 3 a add 2 c.c. water sample. 

 To Tubes No. 4 and 4a add 5 c.c. water sample. 

 To Tubes No. 5 and 5a add 10 c.c. water sample. 



4. Put up all the tubes in Buchner's tubes and incu- 

 bate anaerobically at 42 C. 



NOTE. The bile salt medium is particularly suitable for the 

 cultivation of bacteria of intestinal origin, and at the same time 

 inhibits the growth of bacteria derived from other sources. 



The anaerobic conditions likewise favor the multipli- 

 cation of intestinal bacteria, and also their fermenta- 

 tive activity. The temperature 42 C. destroys or- 

 dinary water bacteria and inhibits the growth of many 

 ordinary mesophilic bacteria. 



5. Pipette 25 c.c. of double strength bile salt broth 

 into flask 6, and 50 c.c. double strength bile salt broth 

 into flask 7. 



6. Pipette 25 c.c. water sample into flask 6, and 50 

 c.c. water sample into flask 7. 



7. Incubate the two flasks aerobically at 42 C. 



8. After twenty-four hours incubation note in each 

 culture : 



a. The presence or absence of visible growth. 



b. The reaction of the medium as indicated by the 

 colour change, if any, the litmus has undergone. 



c. The presence or absence of gas formation, as 

 indicated by a froth on the surface of the medium, and 

 the collection of gas in the inner "gas" tube. 



