378 BACTERIOLYSINS 



The largest number of bacteria that a constant quantity of serum has been 

 able to kill furnishes a measure as to its bactericidal power. 



After a few technical details have been mastered, this method is 

 quickly performed and yields fairly constant and reliable results. It is 

 not adapted for the titration of old immune serums, but is a ready clin- 

 ical test, finding a special field of usefulness in determining the bacteri- 

 cidal powers of the blood after typhoid immunization. 



Requisites for Carrying out the Test. 1. A specimen of the patient's 

 blood is collected aseptically, a process that may be accomplished by 

 thoroughly cleansing the finger with alcohol and collecting blood in a 

 sterile Wright capsule, or better, perhaps, by means of venipuncture, 

 when from 2 to 5 c.c. may be collected aseptically in a sterile centrifuge 

 tube. The control blood from a healthy individual may be collected 

 in a capsule. The serums are carefully separated and pipeted into small 

 sterile test-tubes; 1 c.c. of each is ample for the test. 



2. A twenty-four-hour-old broth culture of the test organism (a 

 young culture is required, because such a culture contains a few dead 

 microorganisms and the absorption of bactericidal elements by dead 

 organisms is thus avoided). 



3. About two dozen " looped pipets," made according to the direc- 

 tions given in Chapter I. 



4. Sterile neutral broth for making dilutions and cultivations. This 

 is prepared and sterilized in the usual manner, from 5 to 10 c.c. being 

 placed in test-tubes. When working with the typhoid bacillus a special 

 broth containing 1 per cent, of mannite and sufficient litmus to color 

 it a deep blue (Smallman) should be on hand. 



5. Two dozen small test-tubes, plugged and sterilized, for making 

 dilutions of the culture. 



Preparation and Enumeration of the Bacterial Culture. As the prin- 

 ciple of the test depends upon measuring the bactericidal activity of the 

 blood according to the number of organisms that are killed, it is neces- 

 sary to prepare somewhat high dilutions and count the number of 

 organisms in a unit volume in each dilution. 



For this purpose place 10 sterile test-tubes in a rack, and arrange 10 

 sterile Petri dishes on the table to correspond to these. To the first 

 tube add 4.9 c.c. of plain sterile broth; to the second, fourth, sixth, 

 eighth, and tenth tubes add 1 c.c., to the third, fifth, seventh, and ninth 

 tubes, add 4 c.c. 



With a sterile graduated 1 c.c. pipet add 0.1 c.c. culture to the first 

 tube and then discard the pipet by placing it in a cylinder of disinfecting 



