Effect of Vitamin A on Listeria monocytogenes Infection in a Silkworm Model

Abstract

Insect infection models have been used increasingly to study various pathogenic agents in evaluations of pathogenicity and drug efficacy. In this study, we demonstrated that larvae of the silkworm Bombyx mori are useful for studying Listeria monocytogenes infections in insects. Infection with the L. monocytogenes wild-type strain induced silkworm death. Infection by a listeriolysin O (LLO) deletion mutant also induced silkworm death, but the bacterial numbers in silkworms were lower than those of the wild-type strain. Intracellular growth was observed when the silkworm ovary-derived cell line BmN4 was infected with the wild-type strain. Explosive replication was not observed in BmN4 cells infected with the LLO mutant and the bacterial numbers of the LLO mutant were lower than those of the wild-type strain. Pretreatment with vitamin A did not affect silkworm mortality after bacterial infection, but the efficiency of infecting the hemocytes and BmN4 cells was decreased with vitamin A treatment. Our results indicate that silkworm larvae are a useful insect infection model for L. monocytogenes and that vitamin A has protective effects against bacterial infection in silkworms.

Silkworm as an experimental animal for research on fungal infections

“…Silkworm infection models have been established for human pathogenic bacteria such as Staphylococcus aureus , Streptococcus pyogenes , Pseudomonas aeruginosa , pathogenic Escherichia coli , Listeria monocytogenes , Serratia marcescens , and Vibrio cholerae . Silkworms are also killed by injection of extracellular toxins, such as α‐toxin and β‐toxin of S. aureus , exotoxin A of P. aeruginosa , diphtheria toxin, and hemolysin of B. cereus .…”

A Silkworm Infection Model for Evaluating <i>In Vivo</i> Biofilm Formation by Pathogenic Fungi

“…Therefore, silkworms infected with pathogenic bacteria can be treated with antibiotics. Based on this research, various silkworm infection models using pathogens such as bacteria and fungi have been established 27,29,[34][35][36][37][38][39][40][41][42] . Silkworm infection models are primarily used for two purposes: one is to identify virulence-related genes to elucidate the infection mechanisms of pathogens, and the other is to discover compounds that can treat infections caused by human pathogens.…”

Facilitating Drug Discovery in Human Disease Models Using Insects

“…Many infectious disease models using insects such as nematodes, fruit flies, greater wax moths, and silkworms have been established. 9,13,14,17,[25][26][27][28][29][30][31][32][33][34][35][36] These infection models are based on the death of insects with the administration of pathogenic microorganisms. Large-scale in vivo screening has identified virulence genes of pathogens and defense-related genes of hosts.…”