CLOSTRIDIUM TETANI 889 



a fuzzy appearance. Isolated colonies of the normal motile type of CI. tetani are 

 extremely difficult to obtain, owing to the tendency of the organisms to spread 

 in a proteus-like or a delicately rhizoidal film over the surface of the agar ; but it 

 is stated that non-motile variants give rise to separate discrete colonies, even on 

 moist media. 



Deep Glucose Agar Shake. — 4 days at 37° C. Slight gas formation ; medium disrupted 

 in 2 or 3 places. Colonies scattered throughout medium, except at surface ; 

 they are rounded, 1-2 mm. in diameter, with sometimes a brownish opaque centre 

 and a Ughter more translucent periphery ; fuzzy, filamentous, branching edge. 



Agar Slope.-^4: days at 37° C. Scanty to moderate, 



greyish-yellow, almost transparent, effuse growth, ^ " 



stretching to sides of tube, with very finely granular, 

 glistening surface. If inoculated into condensa- 

 tion water, spreads rapidly over the whole surface 

 of the agar, and presents a filamentous edge at 

 the top. 



Gelatin Stab. — 10 days at 23° C. Poor growth of fir-tree 

 appearance. At 37° C. liquefies gelatin in a week. 



Broth. — 4 days at 37° C. Poor to moderate growth with 

 slight turbidity, and a finely granular deposit, not 

 disintegrating on shaking. Odour of manure. 



Loeffter's Serum.-4 days at 37° C. Poor, effuse, mostly ^^«- ^^0. -Clostridium tetani. 



discrete growth ; serum may be softened or dis- Surface colony on agar anaero- 



, J r. ijix i 1- bically, 2 days, 37 C show- 



mtegrated after several days, but no true hque- ing parent colony surrounded 



faction occurs. by an effuse outgrowth 



Horse Blood Agar Plates. — 3 days at 37° C. Rounded, ( x 8). 



2-5 mm. in diameter, effuse, greyish, translucent 



colonies, with finely granular surface and lobate or fimbriate edge. Sometimes 

 zone of a-prime haemolysis, diam., 1-5 mm., later passing into the jS-type. 



Coagidated Egg. — 4 days at 37° C. Poor, effuse, partly confluent growth ; no digestion. 



Cooked Meat Medium. — 4 days at 37° C. Good growth ; fluid shows moderate turbidity ; 

 some gas production ; no blackening, and no digestion of meat. Slight blacken- 

 ing is said to occur after some weeks. 



Resistance. — Spores resist boiling for 15 to 90 minutes. Killed at 105° C. in 3 to 25 

 minutes ; killed by 5 per cent, phenol in 15 hours. 



Metabolic. — Strict anaerobe. Opt. temp. 37° C. Grows poorly at 20° C. a-prime or 

 jS-hsemolysis on blood agar plates. Haemolysin acts on R.B.C. of rabbit, goat, 

 sheep, horse, and many other animals. Nutritional : grows fairly well on 

 ordinary media ; growth improved by blood and serum ; not by glucose. Tul- 

 loch's exhausted medium is particularly suitable. Produces green fluorescence 

 on MacConkey's agar. Possesses slight proteolytic properties. 



Biochemical. — Ferments no sugars. Indole -[- ; M.R. — ; V.P. — ; nitrites not produced 

 in nitrate broth ; NH3 slight + ; HgS — ; M.B. reduction — ; catalase — . Litmus 

 milk : reduction of Utmus, usually slight precipitation of casein, sometimes no 

 change. Said to form phenol. 



Antigenic Structure. — Diflferentiated by agglutination into at least 10 types, of which Types I 

 and III appear to be the commonest in this country. Toxm formed by all types is 

 identical and is neutrafized by antitoxin prepared against any one type. Anti- 

 bacterial sera contain agglutinins and opsonins specific to each type. 



Pathogenicity. — Potent exotoxin formed. Naturally pathogenic to man and horses in 

 particular. Experimentally, mice, guinea-pigs, and rabbits are susceptible, dying of 

 tetanus in 1 to 4 days after subcutaneous injection of a broth culture. Washed 

 spores or bacilli are innocuous. The toxin is very potent, and will kill a mouse 

 in a dose of 00001 ml. Birds are resistant. (See Chapter 77.) 



