[Identification of novel therapeutically effective antibiotics using silkworm infection model]

Most antibiotics obtained by in vitro screening with antibacterial activity have inappropriate properties as medicines due to their toxicity and pharmacodynamics in animal bodies. Thus, evaluation of the therapeutic effects of these samples using animal models is essential in the crude stage. Mammals are not suitable for therapeutic evaluation of a large number of samples due to high costs and ethical issues. We propose the use of silkworms (Bombyx mori) as model animals for screening therapeutically effective antibiotics. Silkworms are infected by various pathogenic bacteria and are effectively treated with similar ED(50) values of clinically used antibiotics. Furthermore, the drug metabolism pathways, such as cytochrome P450 and conjugation systems, are similar between silkworms and mammals. Silkworms have many advantages compared with other infection models, such as their 1) low cost, 2) few associated ethical problems, 3) adequate body size for easily handling, and 4) easier separation of organs and hemolymph. These features of the silkworm allow for efficient screening of therapeutically effective antibiotics. In this review, we discuss the advantages of the silkworm model in the early stages of drug development and the screening results of some antibiotics using the silkworm infection model.