Bacteriophage therapy for management of bacterial infections in veterinary practice: what was once old is new again

Bacteriophages (or phages) are naturally-occurring viruses that can infect and kill bacteria. They are remarkably diverse, numerous and widespread. Each phage has a narrow host range yet a large majority of bacteria studied so far play host to bacteriophages, hence the remarkable phage diversity. Phages were discovered just over 100 years ago and they have been used for treatment of bacterial infections in humans and other animals since the 1920s. They have also been studied intensively and this has led to, and continues to lead to, major insights in the fields of molecular biology and recombinant DNA technology, including that DNA is the genetic material, nucleotides are arranged in triplets to make codons, and messenger RNA is needed for protein synthesis. This article begins with a description of bacteriophages and explains why there has recently been a strong resurgence of interest in their clinical use for treatment of bacterial infections, particularly those caused by organisms resistant to multiple antimicrobial compounds. The history of bacteriophage therapy is briefly reviewed, followed by a review and critique of promising but very limited clinical research on the use of bacteriophages to treat bacterial infections in dogs. Other potential veterinary uses and benefits of bacteriophage therapy are also briefly discussed. There are important practical challenges that will have to be overcome before widespread implementation and commercialisation of bacteriophage therapy can be achieved, which are also considered.