424 



TETANUS 



(3) Anaerobic plates may be prepared directly from the dis- 

 charge of the wound. The isolation of the tetanus bacillus is in 

 many cases a difficult matter, and several methods should always 

 be tried. 



Characters of Cultures. — Pure cultures having been obtained, 

 sub-cultures can be made in deep upright 

 glucose gelatin or agar tubes. In deep 

 glucose gelatin (in which growth is often 

 very difficult to obtain) there commences, 

 an inch or so below the surface, a growth 

 consisting of fine straight threads, rather 

 longer in the lower than in the upper parts 

 of the tube, radiating out from the needle 

 track (Fig. 123). Slow liquefaction of the 

 gelatin takes place, with slight gas forma- 

 tion. In agar the growth is somewhat 

 similar, consisting of small nodules along 

 the needle track, with irregular short offshoots 

 passing out into the medium (Fig. 131, a). 

 There is slight formation of gas, but, of 

 course, no liquefaction. On anaerobic agar 

 plates colonies have under a low power a 

 feathery outline (Fig. 124). Growth also 

 occurs in blood serum and also in glucose 

 bouillon and Eobertson's bullock's heart 

 medium under anaerobic conditions. There 

 is in it at first a slight turbidity, and later 

 a thin layer of a powdery deposit on the 

 walls of the vessel. All the cultures give 

 out a peculiar burnt odour of rather un- 

 pleasant character. In making sub-cultures 

 on fluid media a considerable amount of 

 the original growth should be used for the 

 inoculation. 



Conditions of Growth, etc. — The b. tetani 

 grows best at 37° C. The minimum growth 

 temperature is about 14° C, and below 22° C. 

 growth takes place very slowly. Growth takes place only 

 in the absence of free oxygen, the organism being an anaerobe. 

 Sporulation may commence at the end of twenty-four hours 

 in cultures grown at 37° C. — much later at lower tempera- 

 tures. Like other spores, those of tetanus are extremely resistant. 

 They can usually withstand boiling for five minutes, and can be 

 kept in a dry condition for many months without being killed or 



Fig. 123.— Stab cul- 

 ture of the tetanus 

 bacillus in glucose 

 gelatin, showing 

 the lateral shoots 

 (after Eitasato). 

 Natural size. 



