BACTERIAL COMPLEMENT FIXATION TESTS 185 



The objections to methods using human serum for complement are 

 i. the great variation in the complement content of different human 

 sera; 2. human complement requires about 10 times as much ambo- 

 ceptor as guinea-pig complement and is less sensitive to fixation, and 

 3. the statement is made by some workers that while homologous 

 complement and amboceptor may be efficient yet the complement of a 

 serum will not act upon its homologous antigen. This is not true 

 because the complement of human serum invariably haemolyzes the 

 homologous antigen (human red cells). 



The various precipitate tests that have been proposed are unreliable. The 

 precipitate reactions with bile salts give better results than with lecithin, this latter 

 showing positive results in almost one-half of non-syphilitic cases. 



BACTERIAL COMPLEMENT-FIXATION TESTS 



The two bacterial complement-fixation tests which are used as 

 routine diagnostic methods are those for gonorrhoeal and glanders 

 infections. 



Of course similar tests may be made for typhoid, cholera, etc., but we have more 

 simple and practical methods in the use of agglutination or, in the case of typhoid, 

 blood culture procedures. 



The two best known methods for preparing bacterial antigens are 

 the following: 



1. Emulsify the growth on agar or starch agar (for gonococcus) in salt solution, as 

 described under preparation of vaccines. Heat the emulsion at 6oC. for one or two 

 hours and then count the organisms as for vaccines. 



For gonococcus tests we use an antigen with 4,000,000,000 organisms in i (?.c. 

 This may be used directly as antigen or it may be shaken up with glass beads for 

 several hours to complete disintegration. The antigen can be preserved by the 

 addition of y% trikresol or Y 2 % phenol. For glanders one may use a seventy- 

 two-hour culture in glycerine bouillon, sterilized at 6oC. for two hours and preserved 

 with 0.5% phenol. 



2. Besredka and Gay prepare their antigen by precipitating the saline bacterial 

 emulsion, washed-off agar, with an equal amount of absolute alcohol. Then centrifu- 

 galize, pipette off supernatant fluid and dry the sediment in vacua over sulphuric 

 acid. The dried sediment is made into a 2% suspension with isotonic salt solution. 

 For use this stock solution is diluted. There are also methods in which the bacterial 

 sediment is frozen with carbon dioxide snow and then triturated with crystals of 

 sodium chloride so as to make an isotonic saline emulsion. 



Bacterial sediments can also be dried in calcium chloride desiccators. 



In carrying out bacterial complement-fixation tests we use an amount 



