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Updated: Dec 16, 2025
Characterization of a Pathogenic Escherichia coli Strain Derived from Oreochromis spp. Farms Using Whole-Genome Sequencing
Published on: December 23, 2022
Genome-wide comparison of Carnobacterium maltaromaticum derived from diseased fish harbouring important
HyeongJin Roh1, Bo Seong Kim2, Mu Kun Lee3
1Department of Aquatic life medicine. College of Fisheries Science, Pukyong National University, Busan, Korea.
Abstract:
Although Carnobacterium maltaromaticum has been used as a probiotic in fish, it was reported to cause disease for the first time in Korea. The objective of this study was to understand the differences between pathogenic and non-pathogenic strains. Pathogenicity was tested by challenging rainbow trout with C. maltaromaticum ATCC35586 and 18ISCm isolated from diseased fish, and DSM20342 isolated from a dairy product. We also compared 24 genomes of C. maltaromaticum strains plus the genome of our isolate 18ISCm sequenced in this study. Only the strains from diseased fish caused high mortality with severe histopathological changes. Although all strains shared more than 90% of Ko_id, wecC and xtmA were found only in strains from diseased fish. Interestingly, only strains from diseased fish harboured two wecC paralogs involved in the production of D-mannosaminuronic acid which is a major component of a well-known virulence factor, teichuronic acid. Two wecC paralogs of 18ISCm were increased when they were co-cultured with trout blood cells, suggesting that wecC genes might play a role in virulence. The results of this study show that strains isolated from diseased fish are different from strains derived from food in terms of pathogenicity to fish and the presence of virulence-related genes.
Insights
Carnobacterium maltaromaticum strains from diseased fish are pathogenic to rainbow trout, unlike food-derived strains. These virulent strains possess unique genes, including wecC paralogs, linked to D-mannosaminuronic acid production and virulence.
Area of Science:
- Microbiology
- Fish Pathology
- Genomics
Background:
- Carnobacterium maltaromaticum, previously used as a fish probiotic, has been identified as a fish pathogen in Korea.
- Understanding the genetic and pathogenic differences between C. maltaromaticum strains is crucial for fish health management.
Purpose of the Study:
- To differentiate between pathogenic and non-pathogenic strains of Carnobacterium maltaromaticum.
- To identify genetic markers associated with the pathogenicity of C. maltaromaticum in fish.
Main Methods:
- Pathogenicity testing of C. maltaromaticum strains (ATCC35586, 18ISCm, DSM20342) in rainbow trout.
- Whole-genome sequencing and comparative genomic analysis of 25 C. maltaromaticum strains.
- In vitro co-culture experiments with trout blood cells.
Main Results:
- Strains isolated from diseased fish induced high mortality and severe histopathological changes in rainbow trout.
- Pathogenic strains uniquely possessed wecC and xtmA genes, absent in food-derived strains.
- Two wecC paralogs, involved in D-mannosaminuronic acid synthesis (a teichuronic acid component), were found in pathogenic strains and upregulated when co-cultured with trout blood cells.
Conclusions:
- Carnobacterium maltaromaticum strains from diseased fish exhibit distinct pathogenic potential compared to food-derived strains.
- The wecC gene and its paralogs are potential virulence factors in C. maltaromaticum pathogenicity in fish.
- Genomic and pathogenic differences highlight the need for careful strain selection in aquaculture probiotics.
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