Differentiation of Typhoid and Colon Bacilli 647 



Rothberger* first employed neutral red for the diflferentiation of the 

 typhoid and colon bacilli. When grown in fluid media containing 

 it, the colon bacillus produces a yellowish flourescence, while the 

 typhoid bacillus does not destroy the port-wine color. Savagef and 

 Irons t have made use of the color reaction for the routine detection 

 of the colon bacillus in water. The best adaptation of the method 

 is by Stokes, § who adds it to the various sugar bouillons in the propor- 

 tion of 0.1 gram per liter, and uses the medium in the fermentation 

 tube. The colon bacillus always ferments the sugars and produces a 

 typical color reaction. 



Hiss|| recommends the use of two special media. 



The first consists of s grams of agar-agar, 80 grams of gelatin, '5 grams of 

 Liebig's beef-extract, s grams of sodium chlorid, and 10 grams of glucose to the 

 liter. The agar is dissolved in the 1000 cc. of water, to which have been added 

 the beef-extract and sodium chlorid. When the agar is completely melted, the 

 gelatin is added and thoroughly dissolved by a few minutes' .'boiling. The me- 

 dium is then titrated to determine its reaction, phenolphthalein being used as the 

 indicator, and enough HCl or NaOH added to bring it to the desired reaction^ — • 

 i.e., a reaction indicating 1.5 per cent, of normal acid. To the clear medium add 

 one or two eggs, well beaten in 25 cc. of water; boil for forty-five minutes, and 

 filter through a thin layer of absorbent cotton. Add the glucose after clearing. 



This medium is used in tubes, in which the culture is planted by the ordinary 

 puncture. The typhoid bacillus alone has the power of uniformly clouding this 

 medium without showing streaks or gas-bubbles. 



The second medium is used for plating. It contains 10 grams of agar, 25 grams 

 of gelatin, s grams of beef-extract, 5 grams of sodium chlorid, and 10 grams of 

 glucose. The method of preparation is the same as for the tube-medium, care 

 always being taken to add the gelatin after the agar is thoroughly melted, so as 

 not to alter this ingredient by prolonged exposure to a high temperature. The 

 preparation should never contain less than 2 per cent, of normal acid. Of all 

 the organisms upon which Hiss experimented with this medium. Bacillus typhosus 

 alone displayed the power of producing thread-forming colonies. 



The colonies of the typhoid bacillus when deep in Hiss' medium appear small, 

 generally spheric, with a rough, irregular outline, and, by transmitted light, of a 

 vitreous greenish or yellowish-green color. The most characteristic feature con- 

 sists of well-defined filamentous outgrowths, ranging from a single thread to a 

 complete fringe about the colony. The young colonies are, at times, composed 

 solely of threads. The fringing threads generally grow out nearly at right angles 

 to the periphery of the colony. 



The colonies of the colon bacillus appear, on the average, larger than those of 

 the typhoid baciUus; they are spheric or of a whetstone form, and by transmitted 

 light are darker, more opaque, and less refractive than the typhoid colonies. By 

 reflected light they are pale yellow to the unaided eye. 



Surface colonies are large, round, irregularly spreading, and are brown or yel- 

 lowish-brown in color. Hiss claims that by the use of these media the typhoid 

 bacillus can readily be detected in typhoid stools. 



Piorkowski* recommends a culture-medium composed of urine 

 two days old, to which 0.5 per cent, of peptone and 3.3 per cent, of 

 gelatin have been added. Colonies of the typhoid bacillus appear 

 radiated and filamentous; those of the colon bacillus, round, yellow- 

 ish, and sharply defined at the edges. The cultures should be kept 

 at 22°C., and the colonies should appear in twenty-four hours. 



* "Centralbl. f. Bakt.," 1893, p. 187. 



t "Journal of Hygiene," 1901, i, p. 437, 



tibid., igo2, II, p.,437- 



§ "Jour, of Infectious Diseases," 1904, i, p. 341. 



II "Jour, of Experimental Medicine," Nov., 1897, vol. 11, No. 6. 



