346 THE ALCALlGEtfES DYSENTERY TYPHOID 



is followed by a progressive alkalinity, associated with the liberation 

 of small amounts of ammonia. 1 



All members of the intermediate group produce considerable tur- 

 bidity in plain and sugar broths. A pellicle may develop in plain 

 broth after several days' incubation. Potato: B. paratyphosus 

 alpha grows much like the typhoid bacillus on potato; the growth is 

 nearly invisible on acid potato, but comparatively luxuriant. On 

 alkaline potato the growth is brownish. B. paratyphosus beta pro- 

 duces a brownish growth even on slightly acid potato, which resembles 

 that characteristic of B. coli. 



The members of the intermediate group are all aerobic, facultatively 

 anaerobic. The minimum temperature of growth is about 6 to 8 C., 

 the optimum 37 C., and growth ceases at approximately 44 C. The 

 resistance of the members of the intermediate group to environmental 

 conditions, drying and to chemicals is similar to that of the typhoid 

 bacillus. They are, however, somewhat more resistant to heat; an 

 exposure of fifteen minutes at 70 C. or of five minutes at 75 C., 

 kills the bacilli. This is a point of importance in meats infected 

 with the organisms; temperatures lower than 75 C. in the centre of 

 the meat can not be relied upon to remove danger of infection. Higher 

 temperatures, 100 C., are preferable to remove all danger from the 

 poisonous substances of the bacilli, which are not destroyed by gastro- 

 intestinal digestion. 



Products of Growth. (a) Chemical. Paratyphoid bacilli are rather 

 more active proteolytically than typhoid and dysentery bacilli, but 

 they produce neither phenols nor indol. 2 Dextrose and mannite are 

 fermented with the formation of carbon dioxide and hydrogen, lactic 

 acid, and smaller amounts of acetic and formic acids. Lactose and 

 saccharose are not fermented. Numerous attempts have been made 

 to classify the paratyphoid bacilli into several varieties upon the basis 

 of the fermentation of carbohydrates other than those mentioned 

 above, but the lack of agreement has proved an insurmountable 

 obstacle to their general acceptance. 



(6) Enzymes. The members of the paratyphoid group do not pro- 

 duce soluble proteolytic ferments, and they do not liquefy coagulated 

 blood serum, gelatin, fibrin or egg albumen. Neither lipolytic nor 

 amylolytic enzymes have been demonstrated in cultures of these 

 organisms. 



1 Kendall, Day and Walker, Jour. Am. Chem. Soc., 1914, xxxvi, 1943. 



2 Ibid., 1913, xxxv, 1221. 



