616 STAPHYLOCOCCUS 



in the course of a few days to a disappearance of its hsemolytic and toxic properties, but 

 not to that of its flocculating capacity with antitoxin (see Burnet 1931). Toxoid so pre- 

 pared is antigenic and is sometimes used as a vaccine. Straiiis producing a-lysin are 

 predominantly of human origin. 



^-lysin. — This acts on sheep, ox and human, but not on rabbit, red corpuscles, and 

 causes lysis only after the tubes have stood at room temperature or in the ice-chest over- 

 night — the so-called " hot-cold " lysis (Bigger 1933, Glenny and Stevens 1935). It is 

 more resistant to formahn than the a-lysin, and is usually stated to be more resistant 

 also to heat, the degree of destruction at 57° C. in half-an-hour being much less. According, 

 however, to Kodama and Kojima (1939), it resembles a-lysin in being inactivated more 

 readily at low than at high tempeiatures. It is antigenicaUy distinct from the a-lysin, 

 and can be specifically neutrahzed by a suitable antiserum. It is much less toxic than 

 the a-lysin to rabbits, guinea-pigs and mice (Bryce and Rountree 1936). Intradermal 

 inoculation into guinea-pigs gives rise to no more than a transient erythema (Smith and 

 Price 1938a). Strains producing jS-lysm are predominantly of bovme origin (see Minett 

 1936, Slanetz 1942). 



y-lysin. — Smith and Price (19386) have described the production by a strain of staphylo- 

 coccus of a y-toxin, which causes rapid lysis of the red corpuscles of a variety of animals 

 including the rabbit and sheep, and delayed lysis of rat and guinea-pig corpuscles. It 

 appears to be antigenicaUy distinct from the a- and )3-toxins, though it may have some 

 relationship to the aj-toxin. 



Leucocidin. — The study of the leucocidin content of toxic filtrates has been carried 

 out by two different methods. In the Neisser-Wechsberg (N.W.) method the leucocidin 

 is titrated by its abflity to inhibit reduction of methylene blue by healthy rabbit leuco- 

 cytes. The Panton-Valentine (P.V.) method, described by Panton and Valentine in 

 1932 and modified slightly from that of van der Velde (1894), depends on direct micro- 

 scopic observation of the destructive action of the toxin on human leucocytes. According 

 to the observations of Valentine (1936) and Wright (1936), it would appear that the N.W. 

 leucocidin is identical with the a-hfemolysin, but that the P.V. leucocidin is different 

 from it. Flaum (1938), on the other hand, observed that a practically pure ^-lysm might 

 have a strong leucocidal effect, as tested by the N.W. method, and concluded that the 

 N.W. leucocidin is not always identical with the a-lysin. He suggests, however, that 

 the P.V. leucocidin may be identical with the ^-lysin. In his experience it proved to be 

 more heat stable than the leucocidin associated with the a-lysin. Proom (1937) considers 

 that the a-lysin is able to interfere with the respiratory activity of the leucocytes, as 

 measured by the N.W. technique, but that it has not the same destructive action on the 

 cell and nucleus as is manifested by the P.V. leucocidin. Weld and Mitchell (1942) state 

 that the a-lysin and the N.W. leucocidin agglutinate rabbit leucocytes, and that the 

 agglutination reaction can be used instead of methylene blue reduction for measuring the 

 N.W. leucocidin. 



Enterotoxin. — Some strains of staphylococci, mostly of the aureus species, produce 

 under favourable conditions an enterotoxin that is capable of giving rise to acute food 

 poisoning in man (see Chapter 72). Our information on the properties of this substance 

 is confusing and incomplete. There is no satisfactory method of titrating it, and there 

 is some doubt about its heat stabihty. It is prepared best by growth in a semi-soUd 

 agar medium, such as that described by Dolman and Wilson (1938, 1940). The cultures 

 shoiild be incubated for about 40 hours in an atmosphere containing 10-30 per cent. COg, 

 and should then be passed through cheese cloth and fine filter paper, and centrifuged 

 at high speed. The clear supernatant fluid, which contains the enterotoxin, should be 

 sterflized by gradocol filtration. Tests for its presence and its potency were originally made 

 by feeding filtrates to human volunteers or to monkeys ; but Dolman, Wilson and Cock- 

 croft (1936) pomted out that, provided the a- and ^-toxins were destroyed by heat or 

 formahn, or were neutrahzed by antiserum, the enterotoxin could be demonstrated by 

 its abihty to give rise to vomiting and diarrhoea in kittens injected intraperitoneally. 



