USE OF PHAGES IN EPIDEMIOLOGICAL STUDIES 415 



used. As already pointed out, however, it was later observed 

 that adaptation played only a limited part in the evolution of 

 these typing phages, and that many of the phages used were 

 temperate phages which had contaminated the original phage 

 when attempts were made to adapt the latter to lysogenic 

 strains. In spite of this heterogeneity and obligatory use of 

 pattern reactions for type distinction, the paratyphoid B and 

 typhimurium phage-typing schemes have shown themselves to 

 have an order of reliability approaching that of the more elegant 

 scheme for the typhoid bacillus. Furthermore, the various 

 pattern reactions of each serotype are so distinctive that they may 

 be used for the identification of the organisms concerned when 

 flagellar antigenic deficiencies prevent full characterization 

 according to the Kauffmann-White scheme (Anderson, 1955b). 



An alternative phage typing method, which was devised by 

 Lilleengen (1948), exists for S. typhimurium. This is based on 

 similar principles to the scheme of Felix and Callow. It uses a 

 heterogeneous collection of 12 typing phages and divides the 

 organism into 24 types. It is of interest that transduction was 

 first carried out with a phage isolated from Lilleengen's type 22 

 (Zinder and Lederberg, 1952). 



It has been shown that all the phage types of S. paratyphi 

 B are lysogenic (Scholtens, 1950; Felix and Callow, 1951; 

 Hamon and Nicolle, 1951; Nicolle, Hamon, and Edlinger, 

 1951; Scholtens, 1952, 1955, 1956). The phage or phages 

 carried are characteristic of each type, and it has already been 

 indicated that some of the typing phages are identical with these 

 temperate phages. As with the Vi-types of S. typhi, the spe- 

 cific patterns of sensitivity of the paratyphoid B types to the typing 

 phages are controlled to a considerable extent by the character- 

 istic lysogenicity of each type. Hamon and Nicolle (1951) 

 were able to convert type 1 into type 2 (see Table XXII) with 

 the temperate phage carried by type 2, and type 3a into type 

 BAOR with a phage isolated from type BAOR. Similarly, 

 the temperate phages of types Beccles, Taunton, and Dundee 

 converted type 3a into the respective types from which the phages 



