416 BACTERIOPHAGES 



had been isolated. It is thus clear that in the paratyphoid B 

 typing scheme some phages carry out the dual function of typing 

 and of type determination. 



There is evidence to show that similar phenomena obtain in 

 the typhimurium phage-typing scheme of Felix and Callow. 



7. Phage Typing of Other Salmonellas 



In addition to those described above, phage-typing schemes 

 have been devised for S. paratyphi A (Banker, 1955); S. dublin 

 (Lilleengen, 1950; Williams Smith, 1951c); S . enteritidis {lAWc^n- 

 gen, 1950) ; S. gallinarum and S. pullorum (Lilleengen, 1952) ; and 

 S. thompson (Williams Smith, 1 95 1 a, b) . The aim of phage typing 

 is strictly practical in that the various methods are devised for 

 epidemiological purposes only, and there is thus little to be 

 gained from typing organisms that are uncommon. There are, 

 however, a few further salmonella serotypes to which it might 

 be worthwhile applying the method. In Europe, it would prob- 

 ably be an advantage to have a typing scheme for S. newport, 

 and, on the American continent, for S. montevideo and S. oranien- 

 burg, which are important contaminants of spray-dried Q^g 

 (Medical Research Council, 1947; Edwards, Bruner, and 

 Moran, 1948). 



Typing schemes for other Enterobacteriaceae, based on the 

 principle of pattern reactions, have been devised for Shigella 

 sonnei (Hammerstrom, 1947, 1949), for Escherichia coli of infantile 

 gastro-enteritis (Nicolle, Le Minor, Buttiaux, and Ducrest, 

 1952), and for E. coli of catde (Williams Smith and Crabb, 1956). 



8. Phage Typing of Staphyl 



ococcus aureus 



In the following discussion the term "staphylococcus" signifies 

 coagulase-positive Staphyloccus aureus. 



The present practice of staphylococcal phage typing started 

 effectively with the work of Fisk (1942) who demonstrated wide- 

 spread lysogenicity among staphylococci. Fisk's phages were 

 isolated from a number of different strains of staphylococci and 



