Specific Inhibition of Bacteriophage by Bacterial Extracts

Abstract

There is as yet no final explanation for the specificity involved in bacteriophage action. Burnet 1 claims on the basis of experiments made with the Salmonella group of organisms that the action, in a general way, parallels the serologic definition of the heat stable factors. However, he recognized that several observations made by himself and others are not compatible with this point of view. One of these is the failure to demonstrate inhibition of phage action by means of extracts of bacteria containing specific carbohydrate material.∗

In our experiments positive results were obtained using saline extracts prepared according to the method of Furth and Landsteiner, 3 except that no alkali was employed. The 2 phages employed, antidysenteriae Shiga and anti-B. paratyphosus B were derived from chicken stool filtrates. They were specific in their reactions when tested against these 2 organisms; the anti-B. paratyphosus B phage, however, acted also on B. aertrycke.

The tests were made by mixing serial dilutions of phage in a volume of 0.5 cc. with 0.5 cc. of a 1% solution of the extracts previously run through a Berkefeld filter and incubating the mixture overnight at 37° and 24 hours in the ice-chest. To each of the tubes were added 4 cc. of broth and a few drops of a young suspension of the homologous or test organism. Readings were made on the basis of the amount of growth. The signs ftr, tr, ±, +, +, ±, indicate increasing degrees of turbidity; the letters cl. indicate complete clearing.

It is seen from Table I that the action of the phage against B. dysenteriae Shiga was inhibited by saline extracts of the homologous organism but only to a slight degree by a similar product derived from B. aertrycke.