[Phage endolysins-a novel class of antibacterial agents with a wide range of applications]

As "enzybiotics," endolysins represent a new class of antibacterial agents that are naturally produced at the end of the lytic cycle in bacteriophage-infected bacterial cells to enable the phage particles formed to be released from the inside of the host cell. Their enzymatic effect on the cell wall peptidoglycan, which leads to lysis of the infected bacteria, can also be exerted externally as an applied agent. While the endolysin activity can be directly effective in Gram-positive bacteria, the endolysin must be modified for activity against Gram-negative bacteria so that it can overcome the outer cell membrane. For this reason, and to optimize endolysin specificity and stability, endolysins are increasingly being genetically modified and produced recombinantly, which is relatively easy to achieve due to their modular structure consisting of lytic and binding domains. Endolysins have already found increasing actual or extensively postulated use for preventive, therapeutic, and diagnostic purposes in human and veterinary medicine as well as in food safety, biotechnology, and the One Health sector; however, this still needs to be better substantiated by valid studies. Although, in contrast to phage therapy, the regulatory aspects can follow the approval procedures also required for other pharmaceuticals, only less than a dozen randomized controlled studies of phases 1 to 3 have been initiated or completed in the field of human medicine. Only very few endolysin formulations approved as medical products are currently available on the market and approval as medicinal drugs is being sought for some endolysins.