ACD Pharma has more then 45 years of R&D with bacteriophages. Growing resistance towards antibiotics is quickly becoming the greatest threat to human health. The use of antibiotics in food production is partly to blame. With that backdrop, it was a small sensation when ACD in 2018 got the approval for a phage product that efficiently removes a harmful bacteria and outbreaks of a disease which has antibiotics as its only cure. Bacteriophages, or phages, are the world most numerous organisms. Its only function is to attack and kill their specific target bacteria, and in the process multiply. They are natural predators of bacteria, and Nature’s own biocontrol tools, efficiently ensuring that no single bacterium becomes too dominant in an environment. In other words, bacteriophage-based products do not affect the commensal microflora of the patient or aquaculture farm water, which is a common side-effect of broad-range antibacterials. Our Bacteriophage therapy project was started in 2011 and has seen promising results of phage therapy against many bacterial pathogens common in aquaculture. Our first approved product, CUSTUS®YRS, contains five hundred thousand billion Yersinia-killing phages per liter. As these are added in high density to production water or bio-filters an upper limit for the concentration of Yersinia ruckeri that can possibly prevail in the water is quickly established. If the infection pressure is already higher than this limit, it will quickly fall below the limit and prevent the spread of bacteria to healthy fish. We have several other applications in the pipeline and look forward to launching bacteriophage-products in the future.