Use of silkworm as infection model for novel antibiotic screening and development.

The development of new drugs requires preclinical tests followed by clinical trials aimed at establishing the safety and efficacy of the compound. Usually these studies involve the use of mammalians models (e.g., mice and rats), but due to bioethical issues, the time required for the analyses, and the high costs, in the last few years alternative animal models, as Lepidoptera, have been proposed for the initial screening phase. In this study we evaluated the response of the silkworm Bombyx mori, infected with Staphylococcus aureus, to the treatment with different antibiotics (vancomycin, teicoplanin, and dalbavancin). We monitored the survival rate of the larvae, analysed different cellular and humoral markers of the immune system, and evaluated the bacterial load in the hemocoel, performing experiments at 37 °C to reproduce human physiological conditions. While AMP expression and bacterial load revealed to be inadequate to our purpose, larval survival rate, hemocyte viability, and activity of prophenoloxidase system were the three markers characterized by high reliability and reproducibility, reduced costs of the procedure, quickness of analysis, and easiness of use. For these reasons, they could therefore represent potential tools for the screening process of novel antimicrobial drugs by using silkworm.