NEISSER AND WECHSBERG'S BACTERICIDAL TEST 141 



II. Bactericidal Plate -culture -method. 



(Plattenverfahren) according to Neisser and Wechsberg. 



For the determination of the bactericidal titer of a serum, Neisser and 

 Wechsberg recommended the so-called bactericidal plate-culture method. The 

 principle of it is as follows: the serum to be tested is inactivated; different 

 amounts of this inactivated serum are mixed with a definite constant 

 quantity of bacteria, and a constant quantity of active normal serum is 

 added as complement. This mixture is left in the thermostat sufficiently 

 long to permit the occurrence of bacteriolysis. Now, to determine whether 

 and to what degree death of bacteria resulted from the effect of the 

 reactivated bacteriolysins (or of some bactericidal substance otherwise 

 unknown), agar is added, the mixture plated, and the number of colonies 

 counted. 



Stern and Korte recommend this procedure for clinical purposes, as a 

 substitute for the Pf eiff er test in the diagnosis of typhoid fever. They point 

 out the sparing of animals as one of its advantages. On the other hand, 

 this method consumes much more time and its results are less trustworthy. 

 It has not found a place, therefore, in clinical practice. 



The technique of Stern and Korte is the following: the serum 

 The Tech- f the patient, and that of a person not ill with typhoid as 

 nique of control, are inactivated for one-half hour at 56 C. and i c.cm. 

 the Method. o f each in decreasing dilutions is poured into sterile test-tubes. 

 To each is added 0.5 c.cm. of a twenty-four-hour typhoid 

 bouillon culture diluted in bouillon to i : 5000 or i : 10000. For reactivation 

 0.5 c.cm. of fresh normal rabbit's serum in a dilution of i to 12 in physio- 

 logical saline is added and the whole thoroughly shaken. The tubes are 

 then placed in the thermostat for three hours. The entire contents of 

 each mixture is plated on agar, and after eighteen to twenty-four hours the 

 plates are to be examined. That particular plate is considered to indicate 

 the extreme limit of the bacteriolytic action of the serum in which there is 

 still evident a very great decrease in the number of colonies as compared 

 with the innumerable colonies found on the control plates. 



Certain other controls are necessary: 



1. One tube containing culture and complement. 



2. One containing culture and inactivated immune serum in the highest 

 concentration used. 



3. The same with inactivated normal serum instead of immune serum. 



4. Complement without culture and immune serum to test its sterility. 



5. Immune serum without culture and complement to test its sterility. 



6. One tube containing only culture, to be plated immediately. 



7. One tube, containing only the culture, to be plated after standing in 

 the thermostat for three hours. 



