612 STAPHYLOCOCCUS 



There is general agreement that staphylococci isolated from pathological sources 

 liquefy gelatin more frequently than those isolated from water, air, skin, etc. 



There is likewise general agreement that the orange cocci are more rapid 

 liquefiers than the white, and the white cocci more rapid than the yellow. 



Summing up, it may be said that Staphylococcus aureus liquefies gelatin almost 

 always. Staphylococcus albus frequently, and Staphylococcus citreus sometimes. 



Resistance to Heat and Disinfectants. — The staphylococci are among the more 

 resistant of the non-sporing organisms. In broth or agar tubes sealed with parafiin 

 and kept in the ice-chest, cultures may remain alive for months. Dried on threads 

 they retain their vitality for 3 to 6 months, and from dried pus they have been 

 cultivated after 2 to 3 months. Many of them are heat-resistant, in that they will 

 withstand a temperature of 60° C. for half an hour. In pure culture they resist a 

 concentration of 1 per cent, phenol for 15 minutes, but are killed by a concentra- 

 tion of 2 per cent. Mercuric chloride is a poor disinfectant for staphylococci ; to 

 kill them in 10 minutes a 1 per cent, solution is required. Many of the aniline dyes 

 exert a strongly bactericidal action on the staphylococci — as indeed they do on most 

 Gram-positive organisms. This selective action is made use of in certain technical 

 procedures, such as the isolation of Br. abortus from milk, where it is endeavoured 

 by the incorporation of a dye — gentian violet or crystal violet — to inhibit the 

 growth of Gram-positive organisms. Use is also made of the great susceptibility 

 of staphylococci to the violet dyes in the isolation of streptococci, whose sus- 

 ceptibility to these dyes is very much less, Garrod (1942) (see p. 135). Other 

 dyes, of which malachite green appears to be the strongest and acid fuchsin the 

 weakest, are also employed, usually in a concentration of about 1/10,000 (Oesterlin 

 1925). Most strains of staphylococci are sensitive to penicillin. 



Biochemical Reactions.^ — The ability of the staphylococci to ferment sugars 

 varies greatly according to the strain employed. For this reason it is not possible 

 to classify them on this basis with anything like the same precision as, for example, 

 the coliform group of bacilli. As a rule the golden cocci have the greatest fer- 

 mentative power, the white are less active. There is a wealth of literature on the 

 fermentative capacities of the staphylococci, with a corresponding difference of 

 opinion amongst the various authors as to the importance of the different sugars. 

 Thus, Andrewes and Gordon (1905-6) lay stress on the reactions in maltose, 

 lactose, glycerol and mannitol. Winslow, Rothberg and Parsons (1920), on the 

 other hand, come to the conclusion that the only sugar of differential value is 

 lactose. Working with Staphylococcus aureus and albus, these authors found that 

 68 per cent, of the strains formed acid from glucose, 63 per cent, from maltose, 

 61 per cent, from sucrose, and 49 per cent, from lactose ; salicin, inulin and 

 raffinose were rarely fermented, mannitol and dulcitol never. With these findings 

 most authors disagree, particularly with regard to mannitol, which is generally 

 held to be attacked by Staphylococcus aureus, and frequently by Staphylococcus 

 albus (Dudgeon and Simpson 1928). It is quite clear, however, that it is impos- 

 sible to dogmatize on the reactions of any one strain. Dudgeon (1908), who 

 examined 121 aureus and albus strains on a large number of sugars, found that 

 very few agreed in giving identical results. 



Similarly with litmus milk the reactions are variable. Studying 180 aureus 

 and albus strains, Winslow, Rothberg and Parsons (1920) found that 75 produced 

 acid, clot and peptonization, 60 acid, generally clot, and no peptonization, 22 alkali 

 and peptonization, 16 alkali but no peptonization, while 7 produced no change. 



