166 ANTAGONISMS BETWEEN NONSPECIFIC PATHOGENS 



reactivated by dilution after prolonged incubation (Table 31). Peni- 

 cillin and streptomycin acting on S. aureus phage and its host, at concen- 

 trations of the substances which had no destructive effect on the phage 

 alone, showed that no reduction of the phage occurred when placed in 

 the presence of penicillin-treated cells, whereas a definite decrease took 

 place in the case of streptomycin-treated cells (476). 



A mixture of phage and penicillin caused more rapid killing and lysis 

 of staphylococci than either alone, thus indicating that the penicillin- 

 resistant organisms were killed by the phage and vice versa. Penicillin 

 itself did not affect phage multiplication and did not interfere with its 

 lytic action (425). 



The formation of antiphage agents can be studied by a group of 

 methods, making use of the phage agar plate, phage streak, and agar- 

 diffusion or cup tests. Growth of the antagonist upon the phage-seeded 

 agar, or the diffusion of the antiphage agent into the agar, is followed 

 by flooding the surface with host-seeded agar. Antiphage action is in- 

 dicated by a reduced number of plaques or by a zone of bacterial growth 

 surrounding either the antagonist or the cup containing the antiphage 

 substance (466). 



The use of antibiotics in combating true viruses has so far given only 

 little encouragement. However, the inhibition of growth of typhus 

 rickettsiae by penicillin has been established (361). 



RELATIONSHIPS AMONG VIRUSES 



The cultivation of influenza virus in a simple tissue-culture was 

 found (20) to render the culture unable to support the growth of a 

 biologically distinct strain of the virus added 24 hours later. The tissue- 

 culture, however, was still capable of supporting multiplication of 

 a related virus such as that of lymphogranuloma venereum. When 

 two strains of the influenza virus were added to the tissue-culture simul- 

 taneously, the one added in larger concentration suppressed the growth 

 of the other. 



Numerous reports have been made concerning the interference of one 

 virus by another, and even of inactivated bacteriophage with the active 

 agent of the same strain (1047, 1048). Henle and Henle (404) have 



