Phage Therapy Annotated Glossary

Bacteriophages, or phages, are the viruses of bacteria. Bacterial viruses have been used as antibacterial agents, including clinically, approximately since their discovery, now over 100 years ago. In this age of increasing antibiotic resistance, along with concerns over the health impacts of unintentional microbiome modification due to the use of relatively broad spectrum antibiotics, the idea of using comparatively narrow-spectrum, diverse, and abundant bacteriophages as antibacterial agents has come back into fashion. In fact, the use of phages clinically as antibacterial agents never completely went away, and phages otherwise have been used as antibacterial agents over the decades by apparently millions, particularly in the former Soviet Union. In the course of these efforts, a certain terminology has developed in association with phage therapy, or as has been coopted from more general phage biology to the use of phages as antibacterial agents. Many of these terms and associated concepts, however, are relatively obscure or, in many cases, seemingly misunderstood. Consequently, here I provide a list of phage-therapy relevant terms and definitions, along with associated discussions of phage therapy from the perspective of its terminology, all as written from a phage-therapy pharmacological perspective. The hope is to achieve a more efficient and effective development of phage therapy technologies through a more consistently comprehensible application of concepts and terminology.