The serological classification of Bacteriaceae

Abstract

1. Four different Bacteriaceae possessing the same Vi antigen showed, after exposure to heat, striking differences in the physico-chemical behaviour of the Vi antigen. The most noticeable differences observed were those in the changes in Vi-agglutinability and O-inagglutinability of the bacteria; lesser differences were noted in the agglutinogenic activity of the Vi antigen, and none in its agglutinin-binding capacity.2. Treatment with alcohol altered the TVi antigen of one of the species (Bact. coli5396/38) in a way different from that seen in the other three species.3. On the other hand, dilute acid or alkali produced the same chemical changes in the TVi antigen of all four Bacteriaceae.4. The TVi antigen present in the four Bacteriaceae appears to be one and the same substance; it cannot be differentiated by the customary serological methods. Its different physico-chemical state after exposure to heat or alcohol is, therefore, conditioned by other constituents of the bacterial cell, which may, or may not, be antigenic.5. The simultaneous O- and Vi-inagglutinability resulting from heating at 75° C. is particularly impressive since it does not appear to be specially related to any one of the known antigenic components.6. These findings invalidate the basis on which the L, A and B antigens ofBact. colihave been differentiated.7. There is also no valid reason for designating the labile somatic antigens ofSalmonellaand other Bacteriaceae as K antigens. These antigens have the general characters of the Vi antigen ofSalm. typhi, are demonstrated by methods developed in the study of the typhoid Vi antigen, and are not associated with typical capsules.8. The M (mucoid) antigens ofSalmonellaand ofBact. coliare in many respects different from the Vi antigens and should be classified separately.I gratefully acknowledge the valuable technical assistance received from Mr F. J. Flynn throughout the work reported in this and the preceding papers of this series.