102 ..-:,' . BACTERIOLOGICAL METHODS 



varieties, as B. psittacosis, and B. suipestifer and B. paratyphosus B. 

 They differ from the typhoid group by gas formation in dextrose, 

 and from the colon group by the production of an alkaline reaction 

 in milk. They are concerned in the development of intestinal 

 disturbances such as dysentery and diarrhea. No practical 

 routine working method for the isolation of the Gaertner group 

 has as yet been recommended. Some of the more important 

 cultural characteristics are indicated in the table of Bacteria of 

 the Colon- typhoid Group. 



Another important group of bacteria from the standpoint of 

 the food bacteriologist is the large group of sewage streptococci. 

 They occur in the intestinal tracts of many animals. There 

 are numerous strains of this group and they are somewhat less 

 widely distributed than the colon group. The determination of 

 sewage streptococci adds but little more than may be learned from 

 the colon test and for this reason we shall not enter into any fuller 

 discussion. This statement also applies to the host of other bac- 

 teria and related organisms which are more or less constantly 

 associated with sewage and sewage contaminations. 



For all practical purposes, the presumptive colon bacillus test 

 supplemented, as the special cases may require, with certain 

 special tests, combined with the quantitative counts by the 

 plating method (gelatin media) will give all the information which 

 is necessary to judge of the quality of certain foods, drinks and 

 medicamenta, as far as the contamination with sewage is concerned. 

 These points will be more fully discussed under special heads. 



ii. Possible Contamination of Foods with the Typhoid Bacillus 



Testing food substances and medicamenta for the presence of 

 the typhoid bacillus will never become a regular routine in the 

 food laboratory. On occasion it will become an incidental pro- 

 cedure and must therefore receive some consideration. To under- 

 stand the special significance and importance of this organism 

 as a possible contaminator of foods, it is necessary to enter into 



