Pathological changes in the main immune organs of silkworm infected with Staphylococcus aureus
Keywords:Bombyx mori ;, Staphylococcus aureus;, hemolymph;, midgut
Silkworm Bombyx mori (B. mori), a lepidopteran model organism, has become an important model for molecular biology. It also offers an excellent model to study the innate immunity because of its similarity to human beings. Staphylococcus aureus (S. aureus) is a typical gram-positive pathogenic microorganism that causes serious pneumonia, meningitis, endocarditis and septicemia. In this study, silkworm was used as animal model to study the innate immune responses against the pathogenic bacterial infections. We investigated the median lethal dose (LD50) of S. aureus infection in the silkworm, and the pathological changes in their hemolymph and midgut after infection. The LD50 of S. aureus infecting the silkworms was 4.39 × 104 colony-forming units per milliliter (CFU/mL) after 72 h. The peritrophic membrane of the silkworm showed severe damage after 36 h. Insect hemocytes can participate in various innate immune responses, such as encapsulation and nodule formation. Our results imply plasmacytes of hemocytes can adhere to and spread over S. aureus in the hemolymph and may play an important role in the resistance of the silkworms to S. aureus infection.