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Updated: Dec 7, 2025
Listeria monocytogenes Infection of the Brain
Published on: October 2, 2018
First Report on the Finding of Listeria mnocytogenes ST121 Strain in a Dolphin Brain
Yann Sévellec1, Marina Torresi2, Benjamin Félix1
1Maisons-Alfort Laboratory for Food Safety, Salmonella and Listeria Unit, University of Paris-Est, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), 94700 Maisons-Alfort, France.
Abstract:
Listeria monocytogenes (Lm) is a ubiquitous bacterium that causes the foodborne illness, listeriosis. Clonal complexes (CC), such as CC121, are overrepresented in the food production industry, and are rarely reported in animals and the environment. Working within a European-wide project, we investigated the routes by which strains are transmitted from environments and animals to food and the food production environment (FPE). In this context, we report, for the first time, the occurrence of a ST121 (CC121) strain isolated from a dolphin brain. The genome was compared with the genomes of 376 CC121 strains. Genomic comparisons showed that 16 strains isolated from food were the closest to the dolphin strain. Like most of the food strains analyzed here, the dolphin strain included genomic features (transposon Tn6188, plasmid pLM6179), both described as being associated with the strain's adaptation to the FPE. Like all 376 strains, the dolphin strain contained a truncated actA gene and inlA gene, both described as being associated with attenuated virulence. Despite this fact, the strain was able to cross blood-brain barrier in immunosuppressed dolphin exposed polychlorinated biphenyl and invaded by parasites. Our data suggest that the dolphin was infected by a food-related strain released into the Mediterranean Sea.
Insights
A food-associated Listeria monocytogenes strain (CC121) was found in a dolphin brain, suggesting environmental contamination from food production. This strain, despite having weakened virulence genes, crossed the blood-brain barrier, highlighting potential risks.
Area of Science:
- Food safety
- Microbiology
- Environmental science
Background:
- Listeria monocytogenes (Lm) causes listeriosis, a foodborne illness.
- CC121 strains are common in food production but rare in animals/environment.
- Understanding transmission routes from environment/animals to food is crucial.
Purpose of the Study:
- Investigate Lm transmission routes within a European-wide project.
- Report the first isolation of a CC121 strain from a dolphin brain.
- Analyze the genomic features of the dolphin strain and compare it to food-associated strains.
Main Methods:
- Whole genome sequencing and comparative genomics of 377 CC121 strains.
- Bioinformatic analysis to identify genomic features and virulence factors.
- Epidemiological investigation of Lm transmission pathways.
Main Results:
- A ST121 (CC121) Lm strain was isolated from a dolphin brain.
- Genomic analysis revealed the dolphin strain was most closely related to 16 food-isolated strains.
- The dolphin strain possessed FPE-adaptive genomic features (Tn6188, pLM6179) and attenuated virulence genes (truncated actA, inlA).
- Despite attenuated virulence, the strain invaded the dolphin's brain.
Conclusions:
- The dolphin was likely infected by a food-related Lm strain released into the Mediterranean Sea.
- This finding highlights potential environmental contamination pathways from food production.
- CC121 strains, even with reduced virulence, pose a risk in susceptible hosts and environments.
