614 STAPHYLOCOCCUS 



(B), strains. The sera of rabbits that had been inoculated intravenously with 

 whole cocci reacted specifically to a high titre with the polysaccharides when 

 tested by the precipitation reaction. The polysaccharides were non-antigenic and 

 non-toxic for rabbits and mice, but Type A gave rise on intradermal inoculation 

 of patients with staphylococcal infections to an immediate skin reaction of the 

 " wheal and erythema " type. Besides the carbohydrates, a complex protein 

 substance was isolated from both pathogenic and non-pathogenic strains of 

 staphylococci. This protein, though non-toxic to rabbits and mice, was antigenic, 

 giving rise to precipitins that reacted, however, only with the protein and not with 

 the polysaccharide substances. On intradermal inoculation into susceptible 

 patients the protein evoked a skin reaction of the delayed inflammatory type. 

 Serological observations showed that the protein was responsible for the species- 

 specificity of staphylococci, while the type-specificity was determined by the soluble 

 specific carbohydrate substances. For the differentiation of pathogenic from non- 

 pathogenic strains it was essential to employ the precipitation reaction, using as 

 an antigen either the extracted polysaccharide, the supernatant fluid of centrifuged 

 young broth cultures, or an acid extract of the sedimented organisms. The aggluti- 

 nation reaction was affected by the group protein, and was unfitted for type 

 differentiation. This work has been confirmed by Hegemann (1937) and Peragallo 

 (1937) ; but Thompson and Korazo (1937) have brought evidence of the existence 

 of at least one further polysaccharide, which they term Type C ; and Verwey 

 (1940) claims to have isolated a type-specific protein from staphylococci. Durfee 

 (1942) found that all strains agglutinating with Cowan's sera formed Julianelle's 

 polysaccharide Type A. 



In general, it may be said that the precipitin reaction is more suited for the 

 differentiation of pathogenic from non-pathogenic strains, and the agglutination 

 reaction for the sub-division of the pathogenic strains into types. 



Staphylococci are known to be frequent carriers of bacteriophage. Fisk (1942) 

 took advantage of this to develop a cross-culture method of bacteriophage typing. 

 By this means he was able to classify 44 strains of Staph, aureus into 37 different 

 groups. Our own observations have shown that, if potent lytic filtrates are pre- 

 pared, staphylococci may be typed by a method similar to that used for the Vi 

 phage-typing of typhoid bacilli. Already 21 different types have been established, 

 and the method has proved of considerable value in epidemiological inquiries (Wilson 

 and Atkinson 1945). 



Toxin Production. — When grown under suitable conditions, certain strains of 

 staphylococci give rise to a filtrable toxin having a series of effects which, though 

 described a long time ago by such workers as van der Velde (1894), Denys and 

 Havet (1898), von Lingelsheim (1899), Kraus and Clairmont (1900), and Neisser and 

 Wechsberg (1901), have received intensive study during recent years. This activity 

 followed largely on the reinvestigation of the problem by Parker in 1924. A 

 toxic filtrate is hsemolytic, especially towards rabbit cells ; it has a destructive 

 action on leucocytes ; when injected intradermally into the skin of the rabbit or the 

 guinea-pig it gives rise to necrosis ; and when injected intravenously into the 

 rabbit or mouse it causes acute and fatal toxaemia. 



Toxin formation is a property of pathogenic strains and is therefore limited 

 mainly to the aureus type. Considerable variation exists between different strains, 

 and if toxin is required on a large scale for immunological or other purposes it is 

 important to select a strain with a high toxigenic capacity. Various methods are 



