CLOSTRIDIUM WELOHII 



887 



radially striated periphery with a crenated edge (Fig. 206). Other variant forms 

 have been described, differing in morphology, colonial appearance, and sometimes 

 toxicity (Sordelli, Prado, and Ferrari 1932, McGaughey 1933, Livesay 1933, Stevens 

 1935). 

 Deep Glucose Agar Shake. — 4 days at 37° C. Abundant gas, medium ruptured and 

 driven nearly to plug. Numerous colonies throughout medium ; they are 

 biconvex, 1 mm. long, opaque, with an entire edge. 

 Horse Blood Agar. — 3 days at 37° C. Round colonies, 2-5 mm. in diameter, umbonate, 



greyish-white, with opaque raised centre, and a translucent flattened periphery ; 



surface smooth ; entire edge. Zone of /S-hsemolysis for 1-3 mm. around colony 



in most strains (see p. 861). 

 Agar Slope. — 4 days at 37° C. Good growth consisting of discrete colonies. 

 Gelatin. — 2 days at 37° C. Complete liquefaction. 

 Broth. — 4 days at 37° C. Good growth with moderate turbidity, and moderate powdery 



deposit, disintegrating completely. SUght sour odour. 

 Loeffler's Serum. — 15 days at 37° C. Good confluent, slightly raised growth with crenated 



edge ; no digestion. 

 Coagulated Egg. — 15 days at 37° C. Fairly good, confluent, shghtly raised growth ; no 



digestion. 

 Cooked Meat Medium. — 15 days at 37° C. Good growth ; fluid slightly turbid ; gas 



evolved ; meat turned pink ; no digestion ; acid reaction ; sour odour. 

 Resistance. — Cultures in fermentable carbohydrate media die in a few days owing to the 



effect of the acid produced. In sugar-free protein media, in which spores have 



formed, the organisms may live for months. A suspension containing a million 



spores per ml. is sterilized in 30 minutes at 90° C. and in 5 minutes or less at 100° C. 



(Headlee 1931). 

 Metabolic. — Fairly strict anaerobe. Opt. temp. 37° C. Hsemo- 



lysins and leucocidins are formed by some, but not by 



all strains. Usually gives /^-haemolysis on horse blood 



agar plates ; hsemolyses human and sheep's red cells. 



Nutritional : grows fau'ly well on ordinary media ; 



growth greatly improved by 1 per cent, glucose. Green 



fluorescence on MacConlcey plate. Toxin produced. 



Forms a iibrinolysin. 

 Biochemical. — Acid and gas in glucose, maltose, lactose, sucrose, 



and occasionally saUcin ; not in mannitol ; some strains 



ferment inulin, some glycerol. Indole — ; M.R. -f ; 



V.P. — ; nitrates slight reduction ; NH3 shght + ; 



HgS -f + ; M.B. reduction — ; catalase — . Litmus 



milk : acid, gas, clot — stormy fermentation — occurrmg 



in 12 to 48 hours in a proportion of strains. Type A, 



C, and D strains form acrolein from glycerol. 

 Antigenic Structure. — By agglutination no clear-cut grouping 



is apparent ; considerable overlapping of antigens. 



No obvious relation between agglutination results and 



typing of strains by toxin-antitoxin or biochemical^ 



methods. Antitoxic serum can be readily prepared in 



horses. * 



Pathogenicity. — Apparently 7 different exotoxic substances 



produced, of which up to 5 may be produced by one 



strain. Chief agent in causation of gas gangrene in 



man. May play a part in causation of enteritis, 



appendicitis, and puerperal fever. Causes gas gangrene 



in animals, especially sheep. Experimentally, great 



Fig. 207. — Clostridium 

 welchii. 



Culture in htmus milk 

 anaerobically, 2 4 



hours, 37° C, show- 

 ing stormy fermenta- 

 tion. 



