STAPH YLOCOAGULASE 617 



Inoculation of 1-3 ml. of a potent filtrate into a kitten weighing 350-700 gm. is followed, 

 as a rule within half-an-hour, by lassitude and weakness, unsteadiness of gait, and par- 

 oxysmal vomiting of the projectile type, associated with diarrhoea. The kitten may be 

 iU for several hours, but usually recovers completely. 



How far the kitten test can be regarded as a specific reaction to the enterotoxin is 

 doubtful. Several workers (Rigdon 19386, Jones and Lochhead 1939, Hammon 1941) 

 have reported non-specific reactions after the intraperitoneal injection of control materials. 

 Moreover, Fiilton (1943), working in oru* laboratory, found little relationship between 

 the ability of a filtrate to give rise to vomiting in kittens on intraperitoneal injection 

 and to vomiting in man when taken by the mouth. Other methods of demonstrating 

 the enterotoxin have been suggested, such as the intravenous inoculation of rabbits 

 (Kupchik 1937), of kittens (Davison, Dack and Gary 1938, Davison and Dack 1939), or 

 of monkeys (Segalove and Dack 1941), or the feeding of kittens (Dolman, Wilson and 

 Cockcroft 1936), but none has so far proved as reliable as the feeding of human 

 volunteers. 



The nature of the enterotoxin is still in doubt. Dolman (1943) regards it as distinct 

 from the a- and the /5-toxins. He finds that a pure /?-toxin when injected intraperitoneally 

 into the kitten gives rise to early and repeated vomiting, coming on sometimes within 

 5 minutes and followed by death some hours later. Vomiting caused by the enterotoxin, 

 on the other hand, begins later and is not fatal. Though Slanetz (1942) suggests that 

 the /5-toxin and the enterotoxin are identical, this seems improbable, because a pure ^-toxin 

 is innocuous to man by the mouth (Fulton 1943, Dolman 1943). For the separation of the 

 enterotoxin from the a-toxin, reliance has been placed on the difference in their heat 

 stability. The a-toxin is said to be destroyed by heating at 65° C. in 30 minutes, whereas 

 the enterotoxin is said to withstand boiling for 15-30 minutes or longer. As Fulton 

 (1943), however, points out, this is not a reUable method of differentiation, because the 

 a-toxin, though inactivated by heating at 65° C, is moderately resistant to boiling (see 

 p. 615). It is at present very difficult to say whether the enterotoxin is distinct from the 

 other toxins, or whether it is related to the a-toxin ; but the observation by Dolman 

 (1944) of a strain that produced enterotoxin in the complete absence of a- or j5-toxin suggests 

 that the enterotoxin is distinct from the hsemolytic toxins. The mode of action of the 

 enterotoxin is not yet understood. The observations of BayUss (1940) on the cat and of 

 Richmond, Reed, Shaughnessy and Michael (1942) on the rabbit suggest that its action 

 is peripheral rather than central, and that it affects either the sensory nerve endings or 

 the smooth muscle of the small intestine. 



Staphylocoagulase. — The ability of certain staphylococci to coagulate citrated 

 or oxalated plasma was first described by Loeb (1903-04) and confirmed by Much 

 (1908). Later it was studied by a number of other workers (von Daranyi 1926, 

 Gross 1931a, b, Stephan 1934, Vanbreuseghem 1934, Chapman et. al. 1934, Walston 

 1935). 



For its demonstration about 0-1 ml. of an overnight broth culture of Staph, aureus, 

 or of a broth suspension of an agar slope culture made up to the same density as a broth 

 culture, is mixed with 0-5-1-0 ml. of a freshly prepared 1/10 dilution of human or rabbit 

 plasma in saline. The mixture is incubated at 37° C. for 3-6 hours ; if no clot has appeared 

 by this time, it should be left overnight at room temperature and again examined. The 

 plasma of other animals, such as the horse, ox, sheep, or guinea-pig may be used instead. 

 If kept undiluted in the ice-chest under sterile conditions, citrated plasma remains suitable 

 for several months (Fisk 1940). Since plasma may undergo spontaneous coagulation, 

 a control tube containing plasma alone diluted with saUne should always be put up, as 

 well as tubes inoculated with a known coagulase-positive and a known coagulase-negative 

 strain. Culture media containing fermentable carbohydrates should be avoided, since 

 Neter (1937) has shown that under these conditions many strains form an anti-coagulase 



