ANTISTREPTOCOCCUS SERUM 471 



ANTISTREPTOCOCCUS SERUM. A serum obtained from horses immu- 

 nized by the injection of killed or living cultures of streptococci. There 

 is perhaps justification for the use of the serum in streptococcus infections 

 and in scarlet fever, but it should be used early and in large doses; even 

 then the result is doubtful. Bacteriotropins seem to be the principal 

 antibodies present. 



III. DIAGNOSTIC SEROTHERAPY 



A. AGGLUTINATION REACTIONS 



An agglutinogen is that constituent of bacteria which, when injected 

 into an animal body, will stimulate the production of agglutinin. Ag- 

 glutinin is that substance in the blood serum that will cause clumping 

 of a suspension of homologous bacteria when the two are mixed in proper 

 dilutions. The reaction is very specific. 



This reaction is used for either of two purposes (i), For the identifi- 

 cation of bacteria (agglutinogens) and, (2), For the diagnosis of certain 

 diseases by the agglutinins formed in the blood-stream. Number i is 

 seldom used as there are easier methods of identification, the difficulty 

 being due to the fact that it requires several weeks to immunize an animal 

 for the production of agglutinins; there are, moreover, a few agglutinating 

 serums on the market but they are not used extensively because a consider- 

 able bacteriologic training is required for proper interpretation of results. 



Under Number 2 we have the important Widal test for typhoid and 

 paratyphoid fevers. This test is usually accomplished by pricking the 

 patient's ear and collecting a drop of blood on a piece of paper. This 

 is then taken up in physiologic salt solution and filtered. Then add 

 enough of a filtered suspension of typhoid bacilli to make 50 drops. Make 

 a control tube, using nothing but the bacterial suspension. Let both 

 stand at 37C. for two to four hours. If the serum contained agglutinins 

 for bacillus typhosus there will be a fairly heavy white precipitate of ag- 

 glutinated bacteria in the bottom of the serum tube but not in the control. 



Boss Modification of the Widal Test: The agglutination is observed 

 on a glass slide with the naked eye. 



Bordens Modification of the Widal Test: In this test the serum of 

 the blood is mixed with salt solution and then with a suspension of killed 

 typhoid bacilli, so as to bring the dilution up to i to 50. The positive 

 reaction is determined by noting that the clumps of bacteria sink to the 

 bottom of the test-tube and leave a limpid, clear fluid above a small, 

 white, flocculent, mass of agglutinated bacilli. 



B. PRECIPITATION REACTION 



Precipitogen, precipitin and the precipitate are necessary for this test. 

 Bacterial precipitogen is the precipitin producing substance formed in 



