Studies on Bacteriophage

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Abstract
I. In 2 cases of typhoid, the stools failed to yield typhoid bacilli. In one case, 3 successive stool cultures in which Bacillus coli and B. pyocyaneus were found, were followed by 1 giving no growth at all; but subsequent cultures gave abundant growth of B. coli, with B. pyocyaneus absent from then on. In case 2, a stool culture in which B. coli and B. alkaligenes jecalis were found, was followed by successive cultures revealing a few B. coli colonies. After 1 wk., the number of B. coli colonies appearing on successive culture plates gradually increased, and B. alkaligenes jecalis disappeared. In both cases, negative cultures coincided with convalescence. Investigation of the cause of these negative cultures in both cases revealed potent coli phages in the intestinal tracts. The phage in case 1, while active with some of the B. coli strains isolated from the stools, was inactive with others; it was active with the pyocyaneus strains isolated from successive stools. In addition, an autolytic substance was revealed in the pyocyaneus cultures, destructive against these organisms. In case 2, the coli phage was active with its homologous strain and with B. alkaligenes jecalis. It is supposed that the potent coli phages and other lytic substances caused the negative cultures in both cases; and the activity of these coli phages with heterologous typhoid strains suggested a possible explanation for absence of typhoid bacilli. However, the coli phages in contact with their homologous strains yielded secondary cultures. It may be assumed that the B. coli in the intestinal tract at the time of the negative stool cultures consisted of highly susceptible strains which were completely, or almost completely, destroyed; while the strains of B. coli in the following stools developed a resistance against their corresponding phages.[long dash]II. Pyocyaneus cultures may be affected by 2 substances, the lytic agent and the bacteriophage. The first appears spontaneously, induces chromogenic changes, and leads to an increase in the other enzymotic activities. It is transmissible to a limited extent. The lytic pockets are of irregular form and possess an iridescent effect; they are not sterile. Filtrates of the lytic cultures do not act on heterologous strains of the same sp.; neither does amt. of filtrate influence the no. of iridescent spots. The bacteriophages of pyocyaneus cultures possess all the characteristics of any other known bacteriophage.

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