TYPHOID BACILLUS 325 



TYPHOID BACILLUS. 



Historical. Typhoid bacilli were first seen in sections of tissue 

 from autopsies by Klebs in 1876. Somewhat later Eberth 1 success- 

 fully demonstrated them in sections of mesenteric glands, lymph 

 nodes and the spleen by the use of the recently introduced tissue 

 stains. Gaffky 2 first isolated the organisms in pure culture and 

 established their probable etiological relationship to typhoid fever. 

 Later investigations with more refined methods have completely 

 substantiated Gaffky's observations. 



Morphology Typhoid bacilli are rod-shaped organisms of moderate 

 size, measuring from 0.5 to 0.8 microns in diameter and from 1 

 to 3 microns in length. The dimensions vary within the limits 

 given upon different media, the organisms being as a rule somewhat 

 longer in fluid media than upon solid media. Elongated rods and even 

 filaments are occasionally found in old gelatin and potato cultures. 

 The bacilli have rounded ends and occur as a rule singly or in pairs. 

 They are actively motile, particularly in young cultures grown in 

 0.1 per cent, dextrose broth; plain broth cultures are usually more 

 sluggish. Each organism possesses characteristically from eight to 

 ten peritrichic flagella; rarely as many as twenty may be attached to 

 a single organism. The flagella are somewhat wavy in outline and 

 measure from 6 to 8 microns in length. No spores are produced 

 It was formerly held that typhoid bacilli formed no capsules. Car- 

 pano, 3 and Gay and Claypole, 4 however, have demonstrated capsules 

 around typhoid bacilli grown in blood media. 



The organisms stain readily with ordinary anilin dyes and they 

 are Gram-negative. 



Isolation and Culture. The typhoid bacillus grows readily upon the 

 ordinary media. Colonies on agar plates are round, colorless, flat, and 

 nearly transparent; they attain a diameter of from 0.5 to 1.5 mm. 

 after eighteen to twenty-four hours' incubation at 37 C. Devel- 

 opment in gelatin is less rapid, and the colonies after two to three 

 days' incubation at 20 C. are somewhat brownish in color. A uniform 

 turbidity is produced in plain broth after eighteen hours' growth at 

 37 C.; development in dextrose broth is more intense, but after five 

 to seven days it ceases and the organisms die, due to the accumula- 



1 Virchovvs Arch.. 1880, Ixxxi, 58; 1881, Ixxxiii, 486. 



2 Mitt. a. d. kais. Gesamte, 1884, ii, 370. 



3 Cent. f. Bakt., Orig., 1913, Ixx, 42. 



4 Arch. Int. Med., 1913, xii, 624. 



