105 

 PROCEDURE FOR THE EXAMINATION OF WATER. (BACTERIOLOGICAL) 



D 



Steps in procedure 



Further tests 

 required 



To confirm the presence of the colon group in 

 a tube showing gas, streak out a loop of the 

 medium onto cosine methylene blue agar (or 

 Endo or litmus-lactose agar.) Incubate over- 

 night at 37 C. 



(a) Presence of characteristic colonies on the 

 agar constitutes a Partially Confirmee 

 Test for the colon group. Recorc 

 whether the colony resembles the coli or 

 aerogenes sections. 



(b) If no growth develops on the agar plate 

 it is considered that the gas produced in 

 the fermentation tube was due to anaero 

 bic organisms and not to coli-like forms 

 Record probably anaerobe. 



(c) If characteristic colonies of Bact. coli 

 or its close allies are not present, the 

 plates must be examined further before 

 reporting absence of the colon group. 



1. To determine whether Bact. coli or its close 

 allies is present on a negative or questionable 

 cosine methylene blue (Endo, or litmus-lac- 

 tose) agar confirmatory plate. 



(a) Pick one or two colonies which most re- 

 semble Eact. coli or Bact. aerogenes and 

 plant into lactose broth (or lactose pep- 

 tone water), and incubate for 24 hours at 

 37 C. If 10% or more gas is formed, 

 record colon group present. 



(b) A Gram stain should be made of the col- 

 ony before inoculation into lactose broth 

 to insure that a Gram-negative coli-like 

 form in pure culture is being fished. 



Clark and Lubs medium or glucose broth may be 

 inoculated, if desired to test for the M. R. or V. P. 

 reaction, respectively. 



None 



None 



'E' 



THE COLON INDEX 



Estimation of the Incidence of the Colon Group. It is apparent 

 that all agree in the use of the preliminary enrichment method for the de- 

 termination of the presence of the colon group but a moment's thought 



