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Updated: Jun 26, 2026
Listeria monocytogenes Infection of the Brain
Published on: October 2, 2018
Foci of Listeria monocytogenes persist in the bone marrow
Jonathan Hardy1, Pauline Chu, Christopher H Contag
1Department of Pediatrics, Stanford University School of Medicine, Stanford, CA 94305, USA.
Abstract:
Murine listeriosis is one of the most comprehensive and well-studied models of infection, and Listeria monocytogenes has provided seminal information regarding bacterial pathogenesis. However, many aspects of the mouse model remain poorly understood, including carrier states and chronic colonization which represent important features of the spectrum of host-pathogen interaction. Bone marrow has recently been shown to harbor L. monocytogenes, which spreads from this location to the central nervous system. Bone could, therefore, be an important chronic reservoir, but this infection is difficult to study because it involves only a few bacteria and the extent of infection cannot be assessed until after the animal is sacrificed. We employed in vivo bioluminescence imaging to localize L. monocytogenes bone infections over time in live mice, revealing that the bacteria grow in discrete foci. These lesions can persist in many locations in the legs of mice and are not accompanied by a histological indication such as granuloma or a neutrophil infiltratate. We demonstrate that highly attenuated hly mutants, which have defective intracellular replication, are capable of prolonged focal infection of the bone marrow for periods of up to several weeks. These results support the recently proposed hypothesis that the bone marrow is a unique niche for L. monocytogenes.
Insights
Listeria monocytogenes can establish chronic bone marrow infections in mice. In vivo imaging revealed discrete bacterial foci persisting for weeks, highlighting bone marrow as a potential chronic reservoir.
Area of Science:
- Microbiology
- Infectious Diseases
- Immunology
Background:
- Murine listeriosis, caused by Listeria monocytogenes, is a well-established infection model.
- Chronic colonization and carrier states in this model are poorly understood.
- Bone marrow is a recently identified niche for L. monocytogenes, potentially serving as a chronic reservoir.
Purpose of the Study:
- To investigate the dynamics of L. monocytogenes infection within the bone marrow in live mice.
- To characterize the nature and persistence of bone infections.
- To explore the role of bacterial attenuation in chronic bone colonization.
Main Methods:
- In vivo bioluminescence imaging to track L. monocytogenes in live mice.
- Localization of bacterial growth in discrete foci within bone.
- Assessment of infection persistence in the absence of overt histological signs.
- Utilizing attenuated hly mutants with defective intracellular replication.
Main Results:
- L. monocytogenes establishes focal infections within the bone marrow.
- These lesions persist for extended periods (weeks) in live animals.
- Infections occur without typical histological indicators like granulomas or neutrophil infiltrates.
- Attenuated mutants demonstrate prolonged bone marrow colonization.
Conclusions:
- The bone marrow serves as a significant niche for chronic L. monocytogenes infection.
- In vivo bioluminescence imaging is crucial for studying low-burden bone infections.
- Persistent focal bone infections can occur independently of strong inflammatory responses.
- The findings support the hypothesis of bone marrow as a unique L. monocytogenes reservoir.
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