Phage lysins are enzymes produced by bacterial viruses (phages) at the end of their replication cycle. These enzymes degrade the peptidoglycan layer, resulting in lysis of the infected cell and release of the newly matured phage particles. Recombinantly produced and purified phage lysins constitute a novel class of enzyme-based antibiotics. These are currently developed for human therapy with the first clinical trial showing superiority effect. However, the application potential of phage lysins is much wider and it is anticipated that new markets will be accessed in near future. We aim to expand customized development of phage lysins for treatment of infectious diseases of companion animals. Our approach takes into account the Cross-Health principle, reducing or substituting antibiotics that should be safeguarded for human therapy.