394 IMMUNOLOGY 



strains produce the same kind of toxin, although they may show 

 marked variation in agglutination. 



Cl. Tetani. — CI. tetnni has been divided into at least six types 

 by the agglutination test but tliese, too, all produce one kind of 

 toxin that is neutralizable by tetanus antitoxin. 



Cl. Botulinum. — An interesting exception to tlie rule that a 

 single toxin is produced by all strains of an organism is to l)e found 

 in Cl. hotulinum. The three types of this anaerobe produce 

 antigenically different toxins althougli all three toxins produce 

 botulism in appropriate test animals. Toxin from Type A is 

 neutralized only by antitoxin for Type A and not by antitoxin pro- 

 duced against the toxin of Type B or C. This holds true for each 

 toxin. Neutralization and protection tests, rather than agglutina- 

 tion, are the final criteria in identifying these organisms. 



E. Typhosa (B. typhosus). — E. typho.<ia shows a greater uni- 

 formity of antigenic properties possessed ])y various strains tlian 

 any other organism. For this reason, the agglutination test, as 

 previously mentioned, is quite generally used in the final identifica- 

 tion of an organism resembling E. tifphofia culturally and other- 

 wise. Its somatic antigenic relationship to other organisms has 

 already been discussed. Attention is called elsewhere to the 

 relative inagglutinability of strains containing "Vi" antigen. 



From the foregoing remarks, it will be seen that in determinative 

 bacteriology, frequently many factors mu.st be considered before 

 final classification can be accomplished. 



Pneumococcus Typing. — The pneumococcus is usually identified 

 as a capsulated, gram-positive, lance-shaped diplococcus that is 

 bile-soluble and pathogenic for white mice. By means of the 

 agglutination and quellung reactions, pneumococci have been di- 

 vided into fifty-five specific types such as I, II and III, etc., and an 

 heterogeneous group. (Cooper et al., 1929-1932; Walter, Guevin 

 and others, 1941.) 



Beasons for Typing. — Specific type determination is done usually 

 for three reasons : first, because some clinicians desire to treat 

 certain types of pneumococcus pneumonia with immune serum 

 specific for the type, for there is considerable evidence that it is 

 of some therapeutic value especially in Type I infections. The 

 results in Types II and III infections have been less favorable. 



