360 



THE COL/ CLOACA PROTEUS GROUP 



tinction between the three types is no longer made. It is not deter- 

 mined whether B. zopfii is a separate variety of B. proteus. 



The organisms grow vigorously in milk, causing slight acidification 

 and peptonization. The development in broth is equally vigorous; 

 acid and gas are produced in dextrose and saccharose broths. 1 Neither 

 acid nor gas is formed in lactose broth. 2 



Proteus bacilli grow slowly at C. 3 and at temperatures not 

 exceeding 43 to 45 C. The optimum temperature is about 25 C. 

 but development is rapid at 37 C. Strains obtained from putrefying 

 organic matter are tolerant of considerable degrees of alkalinity 4 

 and acidity; 5 those from the human body are somewhat less tolerant. 

 The growth of B. proteus at low temperatures is of considerable prac- 



FIG. 50. Bacillus proteus, flagella stain. X 1500. (Gunther.) 



tical importance; several cases of ptomain poisoning have been 

 attributed to foods decomposed by this organism at the temperature 

 of the ice-box. The resistance of the organisms to heat is not great. 

 According to Meyerhof, 6 an exposure of twenty-five to thirty-five 

 minutes at 54 C., five to ten minutes at 56 C., and of one-half a 

 minute at 60 C., kills them. Their resistance to disinfectants is 

 similar to that of B. coli. 



Products of Growth. (a) Chemical. Proteus bacilli decompose 

 proteins and protein derivatives energetically. The following sub- 

 stances have been detected among the cleavage products: trimethy- 

 lamine, betain, phenol, hydrogen sulphide ; 7 from the decomposition of 



1 Theobald Smith, Fermentation Tube, Wilder Quarter Century Book, 1893, p. 213. 



2 The bacilli may gradually lose their ability to ferment saccharose; strains which 

 do not ferment this sugar may be mistaken for paratyphoid bacilli, particularly if the 

 gelatin-liquefying power disappears simultaneously. The very considerable production 

 of ammonia in sugar-free broth readily distinguishes the proteus bacilli. Kendall, Day, 

 and Walker, Jour. Am. Chem. Soc., 1913, xxxv, 1231. 



3 Levy, Arch. f. offentl. Gesundhpf. in Els. Lothr., 1895, xvi, Heft 3. 



4 Deelman, Arb. a. d. kais. Gesamte, 1897, xiii, 374. 

 6 Fermi, Centralbl. f. Bakt., 1898, xxiii, 208. 



6 Centralbl. f. Bakt,, 1898, xxiv, 20. 

 7 Emmerling, Ber. chem. Gesell., 1896, 2711. 



