20200512260
20210621021208
yjma@shou.edu.cnyjma@shou.edu.cn
scxb
scxb
1000-0615
31-1283/S
2021
45
6
Flavobacterium psychrophilum from Oncorhynchus mykiss]]>
2021
20200512260
Oncorhynchus mykiss;Flavobacterium psychrophilum;genotype;serotype;antimicrobial resistance;pathogenicity]]>
rRNA比对结果显示,CH06和CH07株与嗜冷黄杆菌模式株NBRC 15942的同源性分别为99.35%和99.42%。综合菌株理化和分子特性确定CH06和CH07株为嗜冷黄杆菌。利用多重PCR方法鉴定CH06和CH07株的血清型均为1型(Fd型);多位点序列分型(MLST)分析表明,CH06和CH07株的基因型分别为ST-12和ST-78型,且均属于CC-ST10克隆型。人工感染结果显示,CH06和CH07株对虹鳟幼鱼具有较高致病性,其半致死浓度(LD50)分别为7.1×105和1.1×105 CFU/mL,攻毒剂量与临床病症出现时间呈反比,从人工感染实验鱼的肌肉、脾脏等组织中可重新分离到嗜冷黄杆菌。组织病理变化显示,病鱼肝细胞肿胀,空泡变性,部分肝细胞溶解坏死,细胞核溶解消失;脾脏充血、出血,淋巴细胞减少,红细胞和含铁血黄素增多;肌纤维间隙增宽、断裂、弯曲不齐,部分肌细胞肌浆溶解呈蜂窝状。CH06和CH07株对10种抗菌药物的耐药谱略有不同,均对氨苄西林和甲氧苄啶-磺胺甲噁唑敏感;CH06株对恩诺沙星、氟苯尼考等耐药,而CH07株对恩诺沙星和氟苯尼考中度敏感。本研究首次报道了我国虹鳟源嗜冷黄杆菌的分离鉴定及生物学特性,以期为虹鳟细菌性冷水病的防控提供科学依据。]]>
Flavobacterium psychrophilum mainly infects juvenile salmonids and causes great economic loss in salmonid aquaculture worldwide. F. psychrophilum is characterized by a broad geographical distributions and hosts, inducing typical clinical signs of caudal peduncle erosion, skin ulcerations, pale gills, enlarged spleen, ascites and spiral swimming behavior in diseased fish. Although studies have been carried out on the epidemiology and pathogenicity of this bacterium in many countries, there is still no report on F. psychrophilum strains isolated from cultured salmonids in China. In the present study, two pathogenic bacterial strains (CH06 and CH07) were isolated from the muscle lesions of diseased rainbow trout (Oncorhynchus mykiss) using a polyphasic approach. The results indicated that CH06 and CH07 isolates had an egg-like appearance on TYES agar, producing flexirubin-like pigments, and positive for oxidase and catalase. It can hydrolyze gelatin and casein, but cannot hydrolyze starch or use fructose, galactose and esculin. The results of 16S rRNA alignment suggested that the homology of CH06 and CH07 isolates with F. psychrophilum type strain NBRC 15942 strain were 99.35% and 99.42%, respectively. Based on the biochemical and molecular characteristics results, CH06 and CH07 isolates were identified as F. psychrophilum. The multiplex PCR method was used to identify the serotypes of CH06 and CH07 isolates as type 1 (Fd type). MLST analysis indicated that the genotypes of CH06 and CH07 isolates were ST-12 and ST-78, respectively, both belonging to CC-ST10. The artificial infection results indicated that CH06 and CH07 isolates were highly pathogenic to juvenile O. mykiss with the LD50 values of 7.1 × 105 and 1.1 × 105 CFU/mL, respectively. The dosage of the challenge was inversely proportional to the time when the clinical signs appeared. F. psychrophilum was successfully re-isolated from muscle, spleen of artificially infected fish. Histopathological changes showed that the hepatocytes of the diseased fish were swollen and vacuoles degenerated. Some hepatocytes were lysed and necrotic and the nucleus was dissolved. The spleen was congested and hemorrhagic with reduced amounts of the lymphocytes and increased amounts of the red blood cells and the hemosiderin. The muscle fiber gap was widened and broken, with uneven bending. Parts of the muscle cell sarcoplasmic dissolution was honeycomb-like. CH06 and CH07 isolates exhibited slightly different resistance profiles to 10 antibiotics. They were both highly susceptible to ampicillin and trimethoprim-sulfamethoxazole, while CH06 isolate was resistant to enrofloxacin and florfenicol and CH07 isolate was moderately susceptible to enrofloxacin and florfenicol. This is the first report on the biological characteristics of F. psychrophilum isolates recovered from cultured O.mykiss in China, and it is expected to provide scientific support for the prevention and control of BCWD in salmonid aquaculture.]]>
10.11964/jfc.20200512260
20210621021208
929
939
Flavobacterium psychrophilum biology, clinical signs, and bacterial cold water disease prevention and treatment[J]. The Open Fish Science Journal, 2011, 4(1):40-48]]>
Cytophaga psychrophila, the causative agent of bacterial cold-water disease in salmonid fish[D]. Corvallis:Oregon State University, 1987.]]>
Cytophaga psychrophila"isolated from diseased rainbow trout (Oncorhynchus mykiss) in France[J]. Applied and Environmental Microbiology, 1989, 55(7):1796-1800]]>
Flavobacterium psychrophilum[J]. Journal of Advanced Research, 2011, 2(2):97-108]]>
et al. Flavobacterium psychrophilum infections in salmonid fish[J]. Journal of Fish Diseases, 2003, 26(10):563-574]]>
et al. Antimicrobial susceptibilities of Flavobacterium psychrophilum isolates from the Great Lakes Basin, Michigan[J]. Microbial Drug Resistance, 2017, 23(6):791-798]]>
et al. Isolation, identification and virulence factor detection of pathogenic Aeromonas salmonicida from rainbow trout Oncorhynchus mykiss[J]. Journal of Dalian Ocean University, 2018, 33(4):435-443(in Chinese)]]>
et al. Population structure of the fish pathogen Flavobacterium psychrophilum at whole-country and model river levels in Japan[J]. Veterinary Research, 2013, 44(1):34]]>
et al. Genomic characterization of Flavobacterium psychrophilum serotypes and development of a multiplex PCR-based serotyping scheme[J]. Frontiers in Microbiology, 2017, 8:1752]]>
Flavobacterium psychrophilum, invasion into and shedding by rainbow trout Oncorhynchus mykiss[J]. Diseases of Aquatic Organisms, 2000, 43(1):27-38]]>
Flavobacterium psychrophilum in Salmonid Eggs[J]. Fish Pathology, 2010, 45(1):31-36]]>
et al. Progress in research on multilocus sequence typing technique[J]. Bulletin of the Academy of Military Medical Sciences, 2010, 34(1):76-79(in Chinese)]]>
et al. Multilocus sequence typing identifies epidemic clones of Flavobacterium psychrophilum in Nordic countries[J]. Applied and Environmental Microbiology, 2014, 80(9):2728-2736]]>
et al. Genetic diversity of Flavobacterium psychrophilum isolates from three Oncorhynchus spp. in the United States, as revealed by multilocus sequence typing[J]. Applied and Environmental Microbiology, 2016, 82(11):3246-3255]]>
et al. Large-scale analysis of Flavobacterium psychrophilum multilocus sequence typing genotypes recovered from North American salmonids indicates that both newly identified and recurrent clonal complexes are associated with disease[J]. Applied and Environmental Microbiology, 2019, 85(6):e02305-18]]>
et al. Phenotypic and genetic predictors of pathogenicity and virulence in Flavobacterium psychrophilum[J]. Frontiers in Microbiology, 2019, 10:1711]]>
et al. Flavobacterium psychrophilum vaccine development:A difficult task[J]. Microbial Biotechnology, 2014, 7(5):414-423]]>
et al. Antimicrobial susceptibility of Flavobacterium psychrophilum from Chilean salmon farms and their epidemiological cut-off values using agar dilution and disk diffusion methods[J]. Frontiers in Microbiology, 2016, 7:1880]]>
et al. Antimicrobial susceptibility of Flavobacterium psychrophilum isolates from the United Kingdom[J]. Journal of Fish Diseases, 2018, 41(2):309-320]]>
Oncorhynchus mykiss (Walbaum) experimentally infected with Flavobacterium psychrophilum[J]. Journal of Fish Diseases, 2019, 42(3):325-334]]>