Co-infections of Aeromonas veronii and Nocardia seriolae in largemouth bass (Micropterus salmoides)
Co-infections of Aeromonas veronii and Nocardia seriolae in largemouth bass (Micropterus salmoides)
复制标题
大口黑鲈 (Micropterus salmoides) 维氏气单胞菌和鰤鱼诺卡氏菌的共同感染
DOI：
10.1016/j.micpath.2022.105815
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发表时间：
2022-10-08
影响因子：
3.8
通讯作者：
Yu, Denghang
中科院分区：
文献类型：
--
作者：
Xu, Hongsen;Xu, Ruiping;Yu, Denghang
大口黑鲈（Micropterus salmoides）是我国广泛养殖的重要经济鱼类。随着高密度培养技术的应用，M。沙门氏菌通常在水中被不同的病原体感染。特别是，多种病原体的合并感染很常见，这大大超过了单一感染造成的影响。本研究采用脑心浸液琼脂培养法从病鱼体内分离到两株细菌。根据16 S rRNA和gyrB序列测定结果，结合形态学和生理生化特征分析，最终将分离菌株分别鉴定为Veronii气单胞菌和Nocardia seriolae。此外，还鉴定了与致病性相关的肠毒素、脂肪酶、弹性蛋白酶、群体感应、溶血素和粘附素等8个毒力基因。在Veronii分离物中检测到8个编码哺乳动物细胞进入家族蛋白、甘油醛-3-磷酸脱氢酶、分枝菌酰转移酶、硝酸还原酶亚基和假定的细胞毒素/溶血素的毒力基因。seriolae分离物药敏试验表明，A. veronii和N.对卡那霉素、链霉素、庆大霉素、新霉素、强力霉素、四环素、环丙沙星、左氧氟沙星敏感，对阿米卡星、头孢吡唑、氨苄西林、哌拉西林、羧苄西林、苯唑西林、利福平、甲氧苄啶、万古霉素、美罗培南、亚胺培南、磺胺异恶唑耐药。此外，自然发病的鱼还出现了典型的肉芽肿、坏死中心、细胞变性和坏死、出血和炎性细胞浸润等严重的组织病理学变化。测定了A. veronii和N. seriolae分离物的平均浓度分别为7.94 × 105 CFU/g和3.16 × 106 CFU/g鱼重。此外，A. veronii和N. seriolae引起快速和更高的死亡率相比，由单一的细菌挑战。结果表明，A. veronii和N. seriolae参与了M.沙门氏菌和并发的这两种细菌协同加重疾病的严重性。
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.