418 BACTERIOPHAGES 



Salmonella phage typing provides a system for the stable in- 

 traspecific and epidemiological classification of the organisms, 

 on a local, national, and world-wide basis. Staphylococcal 

 phage typing, on the other hand, is particularly valuable in the 

 local sense, for example, in tracing cross infection or following 

 antibiotic resistant staphylococci in hospital wards, or for in- 

 vestigating outbreaks of staphylococcal food poisoning. Thus, 

 as long as the scheme is locally reliable over relatively short 

 periods (which it is) it fulfils its object. But the reliability goes 

 beyond this point, and staphylococcal phage typing as described 

 by Williams and Rippon (1952) has found wide acceptance. 

 Reference to the many instances in which it has proved useful 

 are given by Anderson and Williams (1956). 



The routine staphylococcal typing phages were isolated from 

 lysogenic strains and have been fully described by Rippon (1956). 

 It has been possible to classify them into four serological groups, 

 of which three are currently used in the phage typing of staphylo- 

 coccal strains of human and bovine origin. From the point of 

 view of lytic spectrum, the phages largely fall into five groups. 

 Phages belonging to different lytic groups may nevertheless be 

 serologically indistinguishable. Many attempts at adaptation 

 of the typing phages to different strains of staphylococci hav^e 

 been made and Rippon (1954) and Rountree (1956) claim to 

 have observed host-induced modification in some phages. In 

 view of the widespread lysogenicity found in staphylococci it 

 seems probable that the phage sensitivity patterns of diff'erent 

 strains are controlled, in part at least, by lysogenicity, but this 

 subject has not yet been adequately explored. 



9. Phage Typing of Corymb aderium diphtheriae 



Keogh, Simmons, and Anderson (1938) seem to have been the 

 first workers to attempt the phage typing of the diphtheria 

 bacillus. They used only 2 phages, but their results indicated 

 that the method had a possible future. Fahey (1952) defined 

 9 types of Corynebacterium diphtheriae by pattern reactions with 5 

 phages. The individual phage types recognized did not seem 



