96 PHARMACEUTICAL BACTERIOLOGY 



Gelatin-liquefying organisms may be looked upon with suspicion 

 when found in milk, water and other liquid-food substances intended for 

 human consumption, as has already been explained. 



It should be borne in mind that the colon bacillus is one of a group of 

 some fifteen or more species and varieties of closely related micro-organ- 

 isms which resemble each other in the following particiilars : 



1. Do not form spores. 



2. Do not liquefy gelatin. 



3. Produce acid in milk and cause milk coagulation. 



4. Produce acid and gas in glucose and lactose media. 



5. Produce acid and gas in bile-salt-glucose broth. 



6. Grow well at temperatures ranging from 38° to 42° C. 



In differentiating the colon bacillus, remember that this organism is 

 rod-shaped (2 to 3/ii long by 0.5 to 0.6/i wide), is motile, produces indol, 

 gives rise to pink colonies on lactose (or glucose) litmus agar and reduces 

 neutral red glucose (or lactose) agar with a greenish-yellow fluorescence. 



It should also be remembered that sewage is a highly complex substance 

 and contains micro-organisms in great variety and in great abundance. 

 Among the organisms present are species of Spirillum, Vibrio, Proteus and 

 Beggiatoa in addition to the bacilli and streptococci already mentioned. 

 The typhoid bacillus does not thrive well in sewage. The number of bac- 

 teria present in crude or ordinary sewage (domestic, city, hospital, mixed, 

 etc.) ranges from 1,000,000 to 100,000,000 and more per cc. The work 

 of these organisms is to break down and render soluble and assimilable 

 (for plants) the organic matter composing the sewage, thus assisting the 

 work of rotting bacteria generally. 



The following is a tabulation of the bacteriological testing that should 

 be made of foods (including pastes, catsups, milk, ice creams, water sup- 

 plies, mineral waters, alcoholic beverages, etc.) that may show an excess 

 of bacterial growth or which may be sewage contaminated: 



BACTERIOLOGICAL EXAMINATION 



I. Direct Count. 



1. Bacilli per cc 



2. Cocci, per cc 



II. Plate and Tube Cultures. (Lactose-Htmus-agar.) 



1. Temperature differential test. 



a. (20° C.) Colonies per cc 



b. (38° C.) Colonies per cc 



2. Color differential test. 



a. Pink colonies per cc 



c. Not pink colonies per cc 



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