462 



PATHOGENIC MICROORGANISMS 



Make a smear of the peritoneal exudate and stain by Gram. If 

 the pneumococcus is pure in the peritoneum wash out the peritoneal 

 exudate with a small nipple pipette, with about 3 or 4 o.c. of sterile 

 salt solution into a centrifuge tube. Make a smear from the heart's 

 blood and also take a culture on a blood agar slant from the heart's 

 blood with sterile instruments. 



Centrifuge the exudate previously removed gently at low speed 

 for a few moments to throw down leucocytes and larger particles. 

 Remove the turbid supernatant fluid which should have the maxi- 

 mum turbidity of a well grown broth culture of pneumococei, into 

 another centrifuge tube and throw down the organisms at high 

 speed. Resuspend the sediment in enough salt solution to give a 

 turbid suspension of proper concentration for agglutination reac- 

 tions. With this material agglutinations are set up in small tubes 

 as follows: The table presents the routine method advised by the 

 workers mentioned above. 



TABLE 1 DETERMINATION OF PNEUMOCOCCUS TYPES BY 

 AGGLUTINATION 69 



Incubation for 1 hour at 37 C. 



Circumstances may arise, as in the recent war, where it has 

 been practically impossible to obtain enough mice to carry out the 

 above technique in all cases. In such cases we ourselves have often 

 successfully typed from colonies grown on blood agar plates by 

 microscopic methods, in the unsuccessful cases having typed subse- 

 quently from blood cultures. Avery has recently advised the use 

 of a medium in which the pneumococcus is apt to outgrow other 

 organisms. It depends upon the use of the following medium : 



To 90 c.c. of a suitable meat infusion broth of a P H of 7.8, add 

 5 c.c. of a sterile 20 per cent solution of dextrose to bring it to a 



This table taken from Avery, Chickering, Cole and Docker, loc. cit. 



