Bacillus Tuberculosis, Koch (1882). 



TUBEECT.E BACILLUS. 



Origin.— In tuberculosis of mammals; in lupus vulgaris. The 

 bacillus of chicken tuberculosis is distinct from that of mammals. 



Form. — Very narrow, rather long rods which are smaller than the 

 diameter of a red blood cell. They may be beaded. The ends are dis- 

 tinctly rounded and the bacillus itself may be straight, or more fre- 

 quently is slightly bent or nicked. Occurs usually single, but may 

 form short threads of 3-6 cells. In the sputum, tissues etc., it is fre- 

 quently found in small bunches. Barely, it occurs in branching form 

 and with club-shaped ends. 



Motility.— Has no motion. 



Sporulation. — Frequently shows a number of bright bodies within 

 the cell, but these cannot be considered as true spores (p. 32). The 

 bacillus itself possesses a relatively high power of resistance to heat, 

 desiccation, acids, putrefaction etc. 



Anilin dyes. — It stains very slowly and difficultly with simple ani- 

 lin dyes; readily with hot carbolic f uchsin, or anilin-water fuchsin or 

 gentian violet. When once stained it is difficult to decolor, whereas 

 ordinary bacteria do so readily — distinction from ordinary bacteria. 

 Gram's method applicable, but requires a long exposure to the dye. 



Growth. — Takes place very slowly, so that usually several weeks 

 elapse before it becomes clearly visible. Furthermore, a special tem- 

 perature, at or near that of the body, and special media as blood- 

 serum or glycerin-agar, etc., are necessary. Access of air is also es- 

 sential. The cultures have a characteristic yeast-like odor. It is 

 possible to accustom the tubercle bacillus to grow on ordinary bouil- 

 lon and agar, even at or near the room temperature- attenuation. 



Plates.— ^0 growth has been obtained on plates. Colonies can be readily obtained 

 by malting successive streaks on glycerin-agar or blood-serum. Colonies obtained direct 

 from the sputum are round, white, opaque, and raised, resembling colonies of white yeast. 

 On subsequent culture the colonies form dry, grayish scales. Under the microscope they 

 appear as interwoven, twisted strands of threads. 



Stab culture. — Can be obtained on glycerin-agar. The growth is restricted to the up- 

 per part of the tube. It spreads over the surface as a thick, raised plaque which at first is 

 white, but later becomes yellowish. 



Streak culture. — On glycerin-a^ar or blood-serum it develops an abundant dfy, gran- 

 ular, raised growth, which at first is grayish, but later takes on a light yellow tinge. 



Potato.— In Roux tubes containing 5 per cent, of aqueous glycerin (Fig. 54, p. 315) 

 the growth is thick, yellowish and in ridges. Requires at feast 2 weeks at 39°. 



Bouillon.— One which contains 5-6 per cent, of glycerin is necessary. A dry folded 

 growth covers the surface; the liquid remains clear and a granular sand-like deposit forms. 

 The material planted must float on the surface of the liquid, otherwise the culture will not 

 develop, or but very poorly. Such bouillon cultures, filtered and concentrated, constitute 

 .the so-called tuberculin. 



Oxygen requirements. — Free access of oxygen is necessary for 

 growth. It is a facultative anaerobe (Frankel). 



Temperature. — Optimum at 37-39". Slight variations above or 

 below this stop the growth. It cannot grow at room temperature. 



Behavior to gelatin. — No growth at ordinary temperature. It 

 ■does not peptonize blood-serum. 



Attknuation. — Prolonged artificial cultivation results in partial 

 attenuation. This is especially marked when grown on potato and 

 similar media. Passage of the bacillus through doves or frogs yields 

 an attenuated form which may grow at ordinary room temperature. 

 The tubercle bacillus as found in man possesses a variable virulence. 



Pathogenesis.— See p. 325. Diagnosis.- See p. 324. 



Infection. — Takes place most frequently along the respiratory 

 "tract — Inhalation tuberculosis. May occur through wounds— Inoculation 

 tiiberaulosis, and also through food — Intestinal tuberculosis. In the latter 

 case the bacilli introduced into the intestines may localize in distant 

 -parts of the body. Placental infection may occur. 



322 



