Co-infections of Aeromonas veronii and Nocardia seriolae in largemouth bass (Micropterus salmoides)

文献类型： 外文期刊

第一作者： Xu, Hongsen

作者： Xu, Hongsen;Xu, Ruiping;Wang, Xiaoni;Liu, Jun;Wei, Jin;Lu, Yulan;Yu, Denghang;Liang, Qianrong;Liang, Qianrong;Zhang, Lin;Yu, Denghang

作者机构：

关键词： Micropterus salmoides; Co-infection; Nocardia seriolae; Aeromonas veronii; Pathological study; Virulence factors

期刊名称：MICROBIAL PATHOGENESIS （ 影响因子：3.848； 五年影响因子：3.957 ）

ISSN： 0882-4010

年卷期： 2022 年 173 卷

页码：

收录情况： SCI

摘要： Largemouth bass (Micropterus salmoides) is an important commercial fish species that is widely cultured throughout China. With the application of high-density culture, M. salmoides is usually infected by different pathogens in water. Particularly, co-infection with multiple pathogens was common, which has considerably outweighed the impact caused by single infections. In this research, two bacteria strains were isolated from diseased fish by incubating on brain heart infusion agar. According to the results of 16S rRNA and gyrB sequence, as well as the analysis of morphological, physiological and biochemical features, the isolated bacterial strains were finally identified as Aeromonas veronii and Nocardia seriolae, respectively. In addition, eight virulence genes related to pathogenicity including enterotoxin, lipase, elastase, quorum sensing, hemolysin and adhesion were identified in A. veronii isolate and eight virulence genes encoding mammalian cell entry family proteins, glyceraldehyde-3-phosphate dehydrogenase, mycolyltransferase, nitrate reductase subunits, and putative cyto-toxin/hemolysin were detected in N. seriolae isolate. Drug sensitivity testing indicated that both A. veronii and N. seriolae isolates were susceptible to kanamycin, streptomycin, gentamycin, neomycin, doxycycline, tetracy-cline, ciprofloxacin and levofloxacin, and resistant to amikacin, cefpimizole, ampicillin, piperacillin, carbeni-cillin, oxacillin, rifampicin, trimethoprim, vancomycin, meropenem, imipenem and sulfisoxazole. Moreover, serious histopathological changes, such as typical granulomas with necrotic center, cell degeneration and ne-crosis, hemorrhage and inflammatory cell infiltration, were found in the naturally diseased fish. The LD50 of A. veronii and N. seriolae isolates were 7.94 x 105 CFU/g and 3.16 x 106 CFU/g fish weight, respectively. In addition, the coinfection of A. veronii and N. seriolae induce quick and higher mortality in comparison with those challenged by single bacteria. These results revealed that both A. veronii and N. seriolae participated in the disease outbreaks of the M. salmoides, and concurrent of those two bacteria synergistically exacerbate the disease severity.

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