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Updated: Mar 14, 2026
Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes
Published on: August 9, 2011
Effect of Vitamin A on Listeria monocytogenes Infection in a Silkworm Model
Yussaira Castillo1, Jin Suzuki1, Kenta Watanabe1
1The United Graduate School of Veterinary Science, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8515, Japan.
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.
Insights
Silkworm larvae provide a valuable insect model for studying Listeria monocytogenes infections. Vitamin A treatment showed protective effects against bacterial infection in silkworms, reducing pathogen entry into cells.
Area of Science:
- Microbiology
- Infectious Diseases
- Insect Models
Background:
- Insect infection models are increasingly utilized for studying pathogen behavior and drug effectiveness.
- Listeria monocytogenes is a significant human pathogen requiring robust infection models for research.
Purpose of the Study:
- To evaluate the utility of silkworm (Bombyx mori) larvae as an insect model for Listeria monocytogenes infection.
- To investigate the role of listeriolysin O (LLO) in L. monocytogenes pathogenesis within the silkworm model.
- To assess the impact of vitamin A on silkworm susceptibility to L. monocytogenes.
Main Methods:
- Infection of silkworm larvae and a silkworm cell line (BmN4) with wild-type and LLO-deficient L. monocytogenes strains.
- Quantification of bacterial load within silkworms and cell cultures.
- Assessment of intracellular bacterial growth in BmN4 cells.
- Evaluation of silkworm mortality and infection efficiency following vitamin A pretreatment.
Main Results:
- Silkworm larvae infected with wild-type L. monocytogenes exhibited mortality.
- A listeriolysin O deletion mutant also caused mortality, but with lower bacterial loads compared to the wild-type.
- Intracellular growth of L. monocytogenes was observed in BmN4 cells, with reduced replication by the LLO mutant.
- Vitamin A pretreatment did not alter silkworm mortality but decreased infection efficiency in hemocytes and BmN4 cells.
Conclusions:
- Silkworm larvae serve as a practical and effective insect model for studying Listeria monocytogenes infections.
- Listeriolysin O contributes to L. monocytogenes virulence in the silkworm model.
- Vitamin A demonstrates protective properties against L. monocytogenes infection in silkworms by hindering pathogen entry into host cells.
