viii,;-10 MANUAL OF METHODS FOR PURE CULTURE STUDY 



PRECIPITATION 



The precipitin reaction may be used in the examination and 

 identification of bacterial extracts and autolysates. The reaction 

 involves the mixing of antigen and antiserum, with a resultant 

 precipitate or ring formation if the two are homologous This is one 

 of the most delicate serological methods. Sera ina,y be obtained 

 which detect the specific antigen in dilutions as high as 1:100,000. 

 A serum which will react in dilutions of. 1:10,000 or 1:20,000 is not 

 uncommon. 



PRODUCTION OF PRECIPITINS 



Rabbits are suitable animals for the production of precipitins. It 

 may be necessary to use several rabbits, since some rabbits are 

 refractory. Precipitins for bacterial proteins may be produced in 

 the rabbit by using as antigen bacterial suspensions, filtrates, extracts 

 or autolysates. However, the antigen employed for the m vilro test 

 must be in solution, clear, and free from antiseptics. Clarification 



TABLE 2 



PROTOCOLS FOR THE PRECIPITIN TEST 



*Use ordinary size test tubes for these dilutions. Mix the contents of each tulie 



thoroughly before transferring to another tube for further dilution. 

 fUsing dilutions made in A (above). 

 jOther controls may be added when deemed advisable. 



