Abstract
Although Streptococcus parauberis is the major bacterial pathogen affecting olive flounder, the translocation and dissemination of this pathogen in infected fish are not well understood. Therefore, we conducted real-time PCR and histopathologic examination to monitor the intensity of infection in multiple organs of the olive flounder after challenge with S. parauberis through subcutaneous injection. The bacterial burden in the fish kidney, when sampled at 0, 3, and 7 dpc, was 0, 6.2 ± 4.5 × 105, and 6.7 ± 5.5 × 106 CFU/100 mg of tissue, respectively, indicating that the infection progressed rapidly over time. Of the ten different tissues sampled, the heart and the brain were the major target organs of S. parauberis based on highest copy number as detected by our modified real-time PCR method. Histopathologic examination also showed that S. parauberis caused severe inflammation accompanied by leucocyte infiltration, connective tissue expansion, and a loss of cardiomyocytes in the brain and heart of fish sampled at dpc 7. However, the number of S. parauberis-positive fish at 3 dpc was much higher in the spleen (6/8 fish) than in the remaining organs, suggesting that the spleen is targeted in the early stages of infection relative to the heart (2/8 fish) or brain (3/8 fish). This study provides essential information for studies to find treatments for the effective elimination of S. parauberis in target organs (i.e., the brain and heart) of olive flounder.
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This research was a part of the project titled ‘Omics based on fishery disease control technology development and industrialization (20150242)’, funded by the Ministry of Oceans and Fisheries, Korea.
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Hyunsu Kim declares that he has no conflict of interest. Ahran Kim declares that he has no conflict of interest. Sun Mi Kim declares that he has no conflict of interest. Thanh Luan Nguyen declares that he has no conflict of interest. Yunjin Lim declares that he has no conflict of interest. Heyong Jin Roh declares that he has no conflict of interest. Nameun Kim declares that he has no conflict of interest. Do-Hyung Kim declares that he has no conflict of interest. Yung Hyun Choi declares that he has no conflict of interest. Suhkmann Kim declares that he has no conflict of interest. Heui-Soo Kim declares that he has no conflict of interest. Mee Sun Ock declares that he has no conflict of interest. Hee-Jae Cha declares that he has no conflict of interest.
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All experiments were carried out in accordance with the guidelines and regulation approved by Ethical Committee of Pukyong National University.
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Hyunsu Kim and Ahran Kim have contributed equally to this work.
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Kim, H., Kim, A., Kim, S.M. et al. Genome based quantification of Streptococcus parauberis in multiple organs of infected olive flounder (Paralichthys olivaceus). Genes Genom 39, 897–902 (2017). https://doi.org/10.1007/s13258-017-0553-4
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DOI: https://doi.org/10.1007/s13258-017-0553-4