128 BACTERIOLYSINS AND HEMOLYSINS. 



II. Bactericidal Plate-culture-method. 



(Plattenverfahren) after 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 quan- 

 tity of bacteria, and a constant quantity of active normal serum is added as 

 complement. This mixture is left in the thermostat sufficiently long to per- 

 mit 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 Pfeiffer test in the diagnosis of typhoid. 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 Technique f tne patient, and that of a person not ill with typhoid as 



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



Method. of each in decreasing dilutions is poured into sterile test-tubes. 

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

 lon culture diluted in bouillon to i : 5000 or i : 10000. For reactivation 0.5 

 c.c. of fresh normal rabbit's serum in a dilution of i to 12 in physiological 

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

 placed into the thermostat for three hours. The entire contents of each 

 mixture is plated in agar, and after eighteen to twenty-four hours the plates 

 are to be examined. That particular plate is considered to indicate the end 

 value of the bacteriolytic action of the serum in which there is 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. 



