Studies with Bacteriophages Active against Mucoid Strains of Bacteria

Abstract

Mucoid varieties of Escherichia, Klebsiella, and Aerobacter are susceptible to the action of bacteriophage. The phages that have been isolated from sewage and which act on the Klebsiella are in the main type-specific, and type specificity closely parallels their serol. behavior. Phages acting on mucoid varieties of Escherichia are strain-specific; those attacking Aerobacter strains may be strain- or group-specific. The plaques which appear when appropriate dilutions of phage are layered over Savita agar-plate cultures of mucoid strains consist of a clear area (the true plaque) which are surrounded by translucent bands or zones which vary in size upon first appearance and widen with further incubation until they may cover the entire plate culture. No increase occurs in the size of the plaque. The organisms found within the zone, though not dead, have lost their capsules, and are avirulent. Phage may be isolated from all parts of the zone and from the plaque. This extremely high diffusibility of the phage has been observed only in the presence of mucoid strains of bacteria.