Long-Term Storage of Bacteriophages Reveals Individual Stability Patterns

Stability is an important characteristic of phages in terms of their use in phage therapy and storage in collections. Therefore, the choice of storage conditions is an essential stage for ensuring this parameter. The conditions for the long-term storage of 21 phages with different virion morphology and specificity to various bacteria were studied. The Klebsiella, Proteus, Stenotrophomonas, and Aeromonas phages were stored as a liquid preparation at 4 °C and in freeze-dried form supplemented with skimmed milk (at 4 °C and −20 °C). It was found that all the studied phages retained their infectivity for a year and the storage in liquid at 4 °C was better compared to the other two variants used. The Aeromonas and Stenotrophomonas phages, which were found in the natural environment, turned out to be more stable in all three tested variants than phages against nosocomial agents. In addition, closely related Klebsiella phages were different in terms of long-term infectivity. Apparently, the difference in amino acid composition of structural proteins affects the long-term stability of closely related phages.