880 CLOSTRIDIUM 



phery. Single colonies often difficult to obtain owing to tendency to spread. 

 Variant types have been described on blood agar (Schoenholz 1928). 



Deep Gbtcose Agar Shake. — 4 days at 37° C. Abundant gas formation ; medium dis- 

 rupted and driven up to plug. Colonies throughout medium, varying in size. 

 Large colonies are 1-2 mm. in diameter, having an opaque, brown, spherical or 

 biconvex centre and a large, clear, more translucent, cigarette-in-water edge. 

 Another type consists of a thin, translucent disc with an eccentric opaque nucleus, 

 the edge of the disc being indented at the point nearest the nucleus ; the disc 

 may contain gas bubbles. Types C, D and E form woolly colonies without a 

 central nucleus. 



Agar Slope. — 4 days at 37° C Moderate, confluent, effuse, greyish-yellow, translucent 

 growth with a very finely granular surface, and an irregular villous edge. 



Oelatin.— l days at 31° C. Completely liquefied 



Broth. — 4 days at 37° C. Abundant growth with dense turbidity and a moderate, pow- 

 dery and granular deposit, mostly disintegrating. Rancid odour. Types C, D and E 

 cause little turbidity, but form a flaky deposit, sticking to the sides of the tube, 



Loeffter's Serum. — 15 days at 37° C. Moderate growth of small, discrete colonies ; diges- 

 tion by A and B, but not by C and D types. 



Horse Blood Agar Plates. — 3 days at 37° C. Irregularly round, 2-3 mm. in diameter, 

 umbonate colonies, with smooth centre and curled or fimbriate periphery ; zone 

 of haemolysis, sometimes co-extensive with the colony, sometimes larger ; around 

 the colony blood is clear, transparent, and brown. 



Coagulated Egg. — 21 days at 37° C. Very poor growth. Butt turned bluish-green, and 

 egg partly digested by A and B, but not by C and D types. 



Cooked Meat Medium. — \5 daysatZl° C. Abundant growth ; gas produced ; long column 

 of slightly turbid fluid with digested meat beneath ; blackening. Putrid odour. 

 No digestion by C, D or E tjrpes. 



Resistance. — Spores are destroyed by dry heat at 180° C. in 5 to 15 minutes. Moist heat 

 at 100° C. destroys them in 5 hours, at 105° C. in 100 minutes, and at 120° C. in 

 5 minutes (but see p. 1616). Gelatin cultures remain viable for a year or more. 



Metabolic. — Strict anaerobe. Opt. temp. 35° C. Grows well at 20° C. a-prime haemo- 

 lysis on horse blood agar plates. Haemolysis of human, but not of sheep's red 

 cells. Types A and B are generally proteolytic, digesting gelatin, serum, egg, 

 and meat ; Types C and D digest gelatin only. Nutritional : grows fairly well 

 on ordinary media ; growth not improved by glucose ; tryptophan and the 

 sporogenes factor are both required. Green fluorescent colonies on MacConkey 

 plates. Powerful exotoxin produced, specific to each type. 



Biochemical. — Type A gives acid and gas in glucose, maltose and salicin ; Types B and 

 C do not ferment salicin. Tj^es A and B ferment glycerol ; Type C does not. 

 Indole — ; M.R. — ; V.P. — ; nitrate reduction — ; NH3 -f ; HjS -] — [- ; methy- 

 lene blue reduction — ; catalase — . Litmus milk: fine precipitate of casein, 

 with almost complete digestion in a fortnight ; litmus reduced, reaction alkaline. 



Antigenic Structure. — Two main types, A and B, distinguished by their toxin production. 

 Antitoxin to A does not neutralize toxin of B, nor vice versa. By agglutination and 

 complement fixation the two types can also be distinguished, and are found to 

 contain 3 or 4 sub-types each. Three other types, C, D and E, have been described 

 forming separate specific toxins. 



Pathogenicity. — Types A, B and E cause botuhsm in man. Type C^^ causes Umberneck in 

 chickens and ducks ; C^ causes one type of forage poisoning in horses in AustraHa 

 and U.S.A. ; C also causes botuhsm in equines in South Africa ; D causes lamziekte 

 in cattle in South Africa. (For fuller description see Chapter 72.) The organism 

 itself is a saprophji^e and does not multiply in the body ; it acts entirely by its toxin. 

 Injected subcutaneously, a broth culture of Type A or B is fatal to guinea-pigs, 

 mice, rabbits, cats, monkeys, and often chickens in 1 to 4 days ; symptoms are 



