350 



VETERINARY BACTERIOLOGY 



Morphology and Staining. B. tetani is a rather long, slender 

 rod, 0.5 by 2 to 5 p, with rounded ends, usually single, rarely 

 in short chains. It is motile by means of numerous peritrichic 

 flagella. Capsules are not produced. Spores are formed abun- 

 dantly. Their size and position are so characteristic as to be practi- 

 cally diagnostic. They are spherical, two or three times the diam- 

 eter of the rod, and terminal, giving the organism the appearance 4 

 of a drumstick. The organism stains readily with the ordinary 

 anilin dyes and is gram-positive. 



Isolation and Culture. The isolation in pure culture of B. 

 tetani is attended with considerable difficulty, largely on account 

 of its being an obligate anaerobe. Kitasato first succeeded in 



isolating it by producing tetanus 

 in experimental animals, then 

 inoculating broth, and, after 

 growth had taken place, heating 

 to a temperature of 80 for half 

 an hour. This temperature 

 should destroy all but spores. 

 The broth may then be inocu- 

 lated into agar or gelatin and 

 kept under anaerobic condi- 

 tions. If spores of other an- 

 aerobes are present, it may be 

 necessary to make several con- 

 secutive animal inoculations 

 and isolations. 



The colonies of the tetanus bacillus upon gelatin plates show 

 minute radiating lines of growth from a central nucleus, resembling 

 somewhat those of B. subtilis. Gelatin stabs show an arborescent 

 growth. The gelatin is slowly liquefied. Radiating filaments 

 are also produced in glucose agar stabs. Bouillon is clouded, and a 

 sediment forms. Blood-serum is liquefied. Milk is coagulated, 

 with production of acid. 



Physiology. The optimum growth temperature is 37.5, but 

 the organism multiplies rapidly at room-temperatures. It is an 

 obligate anaerobe, and in pure culture requires practically com- 

 plete exclusion of oxygen. It will develop, however, under aerobic 



Fig. 145. Bacillus tetani, rods and 

 spores (Giinther). 



