Isolation and characterization of pathogenic <Emphasis Type="Italic">Listonella anguillarum</Emphasis> of diseased half-smooth tongue sole (<Emphasis Type="Italic">Cynoglossus semilaevis</Emphasis> Günther) |
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| Authors: | Xiaoqian Tang Li Zhou Wenbin Zhan |
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| Institution: | (1) Laboratory of Pathology and Immunology of Aquatic Animals, LMMEC, Ocean University of China, Qingdao, 266003, P. R. China |
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| Abstract: | Studies were conducted to determine the cause of the acute mortality of half-smooth tongue sole Cynoglossus semilaevis Günther juveniles in a fish farm in Jimo, Shandong Province, China, in June 2006. Gross signs of the diseased tongue sole
included several petechiae and ecchymoses on the body and fin necrosis and hemorrhagic lesion at the base of the fin. Bacteria
were isolated from kidney, liver and hemorrhagic lesions of the diseased tongue sole. Among14 strains, SJ060621 was proved
to be highly virulent to juvenile tongue sole with LD50 value of <1.0×105 colony forming units (CFU) mL−1, while the remaining 13 were avirulent. Among the 16 antibiotics tested, SJ060621 was sensitive to gentamicin and nitrofurantoin.
It was identified as Listonella anguillarum with conventional plate and tube tests in combination with API 20E analysis. 16S rRNA gene and partial HSP60 gene sequenceing
analysis revealed that the strain was highly homologous with L. anguillarum. Examination of the infected musculature by electron microscopy indicated numerous bacteria and lots of macrophages containing
phagocytosed bacteria. Histopathological investigations revealed severe necrotic degenerative changes in the infected organs.
Indirect immunofluorescence assay (IFA) was employed to detect the location of occurrence of bacteria, and bacteria were found
in aggregations in the inflammatory areas in musculature. |
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| Keywords: | half-smooth tongue sole Cynoglossus semilaevis Günther Listonella anguillarum 16S rRNA gene HSP60 gene histopathology IFA |
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