What are bacteriophages?

• Bacteriophages (phages) are an extremely diverse group of viruses which infect and kill bacteria and can be used to treat bacterial infection.
• There is a sizeable body of trial and observational evidence supporting the safety of phages. Efficacy requires enough of the right phage(s) to be administered to the right site(s).
• Phages can be used as an unlicensed medicine in cases where licensed alternatives (i.e. antibiotics) are not meeting clinical needs. This is governed by existing local NHS unlicensed medicines policies, with the quality of imported phage products reviewed by the medicines regulator.
• Patients potentially suitable for phage therapy include those with antibiotic-resistant infections, antibiotic-susceptible infections but clinical recalcitrance, those needing an alternative medical option to prevent high risk surgery, or cases where other factors (like allergy, antibiotic intolerance or renal disease) might prevent the use of appropriate antibiotics.
• In-vitro phage susceptibility testing of patient isolates is essential to match the right phage(s) to the patient’s bacteria.
• Phages generally come in a suspension that can be administered by a wide range of routes, with the goal typically being administration directly to the site of infection. For example, this could be topical administration for a diabetic foot infection, nebulised for a respiratory infection or intravenous for an endovascular infection.