Anti-Mycobacterium activity of microbial peptides in a silkworm infection model with Mycobacterium smegmatis

An in vivo -mimic silkworm infection model with Mycobacterium smegmatis was established. When silkworms were raised at 37 °C following an injection of M. smegmatis cells (1.25 × 10 7 CFU larva −1 g −1 ) into the silkworm hemolymph, they died within 48 h. Under these conditions, four microbial peptides with anti- M. smegmatis activity, lariatin A, calpinactam, lysocin E and propeptin, exerted therapeutic effects in a dose-dependent manner, and these are also clinically used agents that are active against M ycobacterium tuberculosis . These results indicate that the silkworm infection model with M. smegmatis is practically useful for the screening of therapeutically effective anti- M. tuberculosis antibiotics.