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Updated: May 30, 2026

Characterization of a Pathogenic Escherichia coli Strain Derived from Oreochromis spp. Farms Using Whole-Genome Sequencing
Published on: December 23, 2022
Complete genome sequence and comparative analysis of the fish pathogen Lactococcus garvieae
Hidetoshi Morita1, Hidehiro Toh, Kenshiro Oshima
1School of Veterinary Medicine, Azabu University, Sagamihara, Kanagawa, Japan.
The capsule gene cluster is crucial for Lactococcus garvieae virulence in fish. This gene cluster, absent in non-virulent strains, likely contributes to the pathogen's ability to cause disease.
Area of Science:
- Microbiology
- Genomics
- Fish Pathology
Background:
- Lactococcus garvieae causes fatal hemorrhagic septicemia in fish.
- Understanding the genetic basis of virulence is critical for disease control.
Purpose of the Study:
- To compare the genomes of virulent and non-virulent Lactococcus garvieae strains.
- To identify genetic factors contributing to L. garvieae virulence.
Main Methods:
- Comparative genome analysis of virulent (Lg2) and non-virulent (ATCC 49156) L. garvieae strains.
- Sequence analysis of the capsule gene cluster in different strains.
- Identification of potential virulence factors.
Main Results:
- A 16.5-kb capsule gene cluster was present in the virulent Lg2 strain but absent in the non-virulent ATCC 49156 strain.
- Disruption of two genes within the capsule cluster correlated with reduced virulence in strain Lg2-S.
- The capsule gene cluster exhibits characteristics of a genomic island and may encode other virulence factors like haemolysin.
Conclusions:
- The capsule is a key virulence factor for L. garvieae.
- The capsule gene cluster likely represents a horizontally acquired genomic island.
- This study provides insights into L. garvieae virulence mechanisms in fish.
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