A Bacteriophage Feces Media

Abstract

It became desirable in the course of some investigations to develop a media to determine the relative biological stability of fecal B. coli strains to bacteriophage. The relative sensitiveness of the B. coli flora can be altered by diet. The isolation of colonies and testing their phage-sensitiveness is too involved for practical purposes. We wished to develop a media on which we could plate our fecal specimens and read directly the percent of B. coli flora resistant and susceptible to bacteriophage.

Endo, Eosin Methylene Blue, Conradi-Drigalski and Teagues media were used. Fifty cc. of these various agar media were put in flasks and sterilized. After cooling to 50°C. Coli-phage was added in amounts varying from 0.1 cc, 0.3 cc, 0.5 cc, 0.7 cc, 1 cc and 2 cc. and poured into petri dishes. The surface was seeded and smeared with spreader, then incubated for 21 hours. The best results were obtained when 0.3 cc and 0.5 cc. was added to the 50 cc agar media. Increase in concentration of phage causes inhibition of B. coli growth. The eosin methylene blue media has worked best in our hands. These plates must be protected from light. The phage is destroyed or inhibited when exposed to light. Eosin Methylene Blue phage media can be stored for days in the dark in the icebox and retain its original phage content. The B. coli susceptible colonies lose their shining luster, are smaller and irregular. A relatively clear, transparent zone develops around the B. coli phage-sensitive colonies. When viewed against a light background the ratio of phage-resistant to phage-sensitive B. coli colonies can be readily determined.