ISOLATION OF THE STAPHYLOCOCCI 625 



The serum obtained by Proscher (vide ante) agglutinates virulent staphy- 

 lococci in high dilutions (1-2500). 



The serum of a person suffering from a staphylococcal infection has no 

 agglutinating properties. 



SECTION IV. THE DETECTION, ISOLATION AND IDENTIFICATION 

 OF THE STAPHYLOCOCCI. 



In suspected staphylococcal infections the pus, blood and exudates should 

 be examined. 



(a) Microscopical examination. Films and smears made with blood, pus, 

 etc. should be stained : 



1. Some, with one of the solutions containing carbolic acid (Kiihne's 

 blue, carbol-thionin, or dilute carbol-fuchsin). 



2. Others, by Gram's method. The staphylococci are gram-positive and 



""> V$, -^j 



** 



FIG. 295. Staphylococcus aureus. Pysemic abscess of the lung. Gram's 

 stain and eosin. (Oc. 2, obj. ,Vth. Zeiss.) 



by double staining, using eosin for the ground- work, very pretty preparations 

 are obtained. 



(b) Cultures. The Staphylococcus may not be present in pure culture in 

 the original material, and sometimes more than one variety of Staphylococcus 

 may be present, so that methods of isolating the organisms in pure culture 

 will have to be adopted. 



1. Sow a drop of the material in a tube of broth (this will give a culture of 

 all the organisms present). 



2. To isolate the different organisms sow a loopful of the material on the 

 surfaces of three agar tubes without recharging the needle, according to 

 the method described at p. 82. In this way single colonies are obtained 

 which it is quite easy to differentiate. 



Gelatin plates may also be sown, but this method is liable to lead to error, 

 as some organisms such as the pneumococcus and the streptococcus may 

 pass unnoticed. 



Note. In investigating the organisms present in a septic infection it must be 

 remembered that staphylococci are quite commonly found on the surface of the 

 skin, so that every precaution must be taken to eliminate this possible source of 



2R 



