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1.
This study was carried out to investigate the effect of water‐soluble polysaccharides extract of algae Ulva rigida (WPU) as dietary supplement on growth performance, antioxidant enzyme activity, lysozyme and phenoloxidase activity, and resistance of shrimp (Litopenaeus vannamei) subjected to bacterial infection with Photobacterium damselae. Three replicate groups of shrimp (1.0 g) were fed four diets containing four levels, 0 or control, 0.5, 1 and 1.5 g/kg of WPU for 8 weeks over the growth trial. Thereafter, 30 shrimps from each dietary treatment were infected with bacteria P. damselae to evaluate disease resistance of infected shrimp. The results of this study showed that WPU was effective as a growth promoter for L. vannamei. The best growth rate was observed in shrimp fed 1.5 g/kg of WPU diet. Regarding antioxidant defences, the diets supplemented with three levels of WPU stimulated glutathione peroxidase and catalase activates in experimental shrimps. MDA content of L. vannamei‐fed diet containing WPU 1.5 and WPU 1.0 was lower than WPU 0 and WPU 0. 5 diets. Also, lysozyme and phenoloxidase activities of shrimp receiving WPU at 1.0 and 1.5 level were significantly higher than those fed WPU 0 and WPU 0.5 diets. In addition, using WPU extract in all diets decreased mortality in L. vannamei in a dose‐dependent manner after challenge with P. damselae. These results suggest that incorporation of water‐soluble polysaccharides from green algae U. rigida at 1.5 g/kg doses improves growth and antioxidant activity and enhances the immune responses in shrimp L. vannamei.  相似文献   

2.
Mycobacterium spp. and Photobacterium damselae subsp. piscicida are recognized as the most frequent causative agents of granulomatous lesions in fish. Although frequent episodes of mycobacterial infections have been reported in wild fish worldwide, only sporadic cases have been documented to date in Italy. To investigate for the presence of lesions referable to mycobacteriosis and to identify the mycobacterial species involved, a total of 159 wild mullets were fished from the eastern coast of the Ligurian Sea, killed and necropsied. Liver and spleen samples were collected from all fish for histopathological and microbiological analyses. Molecular investigations for identification of Photobacterium damselae subsp. piscicida were performed. Gross examination revealed granulomatous lesions in one animal; microscopically, 42.14% of fish displayed granulomas with various histological features, 19.50% resulted positive at Ziehl–Neelsen staining, and were confirmed as mycobacterial lesions by culture. The identified colonies were characterized as M. fortuitum, M. abscessus, M. flavescens, M. chelonae, M. septicum and M. nonchromogenicum. In all, 35% of animals resulted positive for Photobacterium damselae subsp. piscicida. These data suggest widespread mycobacterial infection also by Photobacterium damselae subsp. piscicida infections in wild fish. Moreover, the pathogenicity of some mycobacterial species, previously considered as saprophytic, was demonstrated.  相似文献   

3.
The availability of a rapid and accurate method for the diagnosis of Photobacterium damselae subsp. piscicida (Phdp), able to discriminate its strictly correlated subsp. damselae (Phdd), formally known as Vibrio damsela, is essential for managing fish pasteurellosis outbreaks in farmed fish. A single‐step, high‐sensitivity real‐time PCR assay for simultaneous detection and quantification of P. damselae was designed targeting partial of the sequence of the bamB gene and tested for specificity and sensitivity on laboratory‐generated samples as well as on experimentally infected seabream tissue samples. With a limit of detection (LOD) of one copy in pure bacterial DNA, the sensitivity was higher than all methods previously reported. Validation in target and non‐target bacterial species proved the assay was able to discriminate Phdd‐Phdp subspecies from diverse hosts/geographical origins and between non‐target species. In addition, two SNPs in the target amplicon region determine two distinctive qPCR dissociation curves distinguishing between Phdp‐Phdd. This is the first time that a molecular method for P. damselae diagnosis combines detection, quantification and subspecies identification in one step. The assay holds the potential to improve the knowledge of infection dynamics and the development of better strategies to control an important fish disease.  相似文献   

4.
The present study aimed to investigate leucocyte responses to inflammation as well as some innate immune parameters of Senegalese sole, Solea senegalensis, following challenge with two strains of Photobacterium damselae subsp. piscicida belonging to the European and Japanese clones described for this bacterium. Pathogenicity assays were performed to assess the virulence of each Photobacterium damselae subsp. piscicida strain for sole. Subsequently, fish were intraperitoneally injected with phosphate‐buffered saline (control) or two concentrations (2 × 102 and 2 × 106 CFU mL?1) of each bacterial strain and sampled after 6 and 24 h. Results showed that the European isolate induces a higher degree of response than the Japanese strain. While blood neutrophilia and monocytosis correlated well with the increase in neutrophil and macrophage numbers in the peritoneal cavity, fish infected with the European isolate presented higher peritoneal cell numbers than fish challenged with the Japanese strain. In addition, alternative complement pathway activity and respiratory burst of head kidney leucocytes increased significantly in fish infected with the European isolate. The enhanced innate immune response displayed by Senegalese sole challenged with the European isolate is probably due to the higher degree of virulence presented by this Photobacterium damselae subsp. piscicida strain.  相似文献   

5.
MALDI‐TOF MS was tested for the identification of Photobacterium damselae subsp. piscicida on isolates grown on two media, cultured at three incubation times and applied on the target plate by the direct sample spotting (DS), by the on‐target extraction (OTE) and by the full extraction (FE) method, in triplicates. The identification of samples grown on blood agar (BA) outperformed identification on tryptic soya agar (TSA) by 0.64% for DS and OTE. The OTE gave the highest scores in both culture media, all incubation times and replicates. Reliable 24‐hr species identification was 61.54%, 84.61% and 53.85% for samples grown on TSA and identified by DS, OTE and FE, respectively. For isolates grown on BA, they were 76.92%, 96.15% and 30.77%, respectively. When identified by OTE, the 48‐hr identification was 93.58%, but for 72 hr declined to 71.79%. The reliable identification with the highest score from the first measurement was 100% only for OTE from BA (24 hr), whereas OTE from TSA gave 84.61% (24 hr), 76.92% (48 hr) and 84.61% (72 hr). The reliable MALDI‐TOF MS identification of Ph. damselae subsp. piscicida is incubation time, media, target plate preparation and replicate‐dependent.  相似文献   

6.
Since 2011, high mortality rates and symptoms consistent with vibriosis have been observed in farmed amberjack (Seriola dumerili) in Japan. To identify 41 strains isolated from diseased amberjack, a multilocus sequence analysis using nine concatenated genes (ftsZ, gapA, gyrB, mreB, pyrH, recA, rpoA, topA and 16S rRNA) was conducted. Twenty‐seven strains were identified as Vibrio harveyi, suggesting an epidemic of V. harveyi infection in amberjack farms. Other strains were identified as Vibrio anguillarum, Vibrio owensii and Photobacterium damselae subsp. damselae. To develop an efficient diagnostic method for vibriosis in amberjack, a multiplex PCR system was developed to identify V. anguillarum, V. harveyi and P. damselae subsp. damselae. The method successfully discriminated between these three bacterial species, with amplification products of 350 bp for V. anguillarum, 545 bp for V. harveyi and 887 bp for P. damselae subsp. damselae and can be used for diagnosis in aquaculture farms.  相似文献   

7.
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8.
Juvenile Atlantic halibut (~100 mg, Hippoglossus hippoglossus) were exposed to Vibrio proteolyticus, a Vibrio spp. isolate, Photobacterium damselae ssp. damselae and five different isolates of Aeromonas salmonicida ssp. achromogenes via an hour‐long bath immersion to ascertain their variation in pathogenicity to this fish species. Results were analysed using Kaplan–Meier survival analysis. Analysis of the data from challenges using A. salmonicida ssp. achromogenes revealed three survival values of zero and a spread of values from 0 to 28.43. Challenges using a Vibrio spp isolate, V. proteolyticus and P. damselae resulted in Kaplan–Meier survival estimates of 31.21, 50.41 and 57.21, respectively. As all bacterial species tested could induce juvenile halibut mortalities, they must all be considered as potential pathogens. However, the degree of pathogenicity of A. salmonicida is isolate dependent.  相似文献   

9.
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10.
Mass mortality has occurred among cultured Nile tilapia, Oreochromis niloticus, on fish farms in Manzala, Dakahlia province, Egypt, in the summer season, 2019. Moribund fish were reported with deep ulcers, septicaemic lesions and sampled for bacterial isolation. In this study, most isolates were subjected to bacteriological examination, antibiotic sensitivity test, 16S rRNA gene sequencing and histopathological examination. Following isolate identification, intraperitoneal challenge of Nile tilapia with a bacterial suspension 2 × 106 CFU/ml was performed. Samples from liver, spleen and kidney were collected for histological and biochemical analysis. The results showed a high similarity (99%) to Photobacterium damselae strains using phylogenetic analysis of 16S rRNA. P. damselae exhibited resistance to amoxicillin and erythromycin, as well it was highly sensitive to chloramphenicol and doxycycline. Moreover, haemorrhage, oedema, hemosiderosis and melanomacrophage activation in the liver and head kidney of infected fish were detected by light and electron microscopy. Also, significant higher levels of CAT and SOD in the spleen and head kidney, as well as the serum levels of NO were observed in experimentally challenged O. niloticus, compared to the control fish. Our data identified P. damselae for the first time from infected Nile tilapia, describing its sensitivity to a variety of antibiotics, histopathological alterations and oxidative stress impact, and it could be useful indicators for understanding P. damselae pathogenesis, which might provide a preventive efficacy for P. damselae.  相似文献   

11.
Cobia, Rachycentron canadum L., is a very important aquatic fish that faces the risk of infection with the bacterial pathogen Photobacterium damselae ssp. piscicida, and there are few protective approaches available that use multiple antigens. In the present study, potent bivalent antigens from P. damselae ssp. piscicida showed more efficient protection than did single antigens used in isolation. In preparations of three antigens that included recombinant heat shock protein 60 (rHSP60), recombinant α‐enolase (rENOLASE) and recombinant glyceraldehyde‐3‐phosphate dehydrogenase (rGAPDH), we analysed the doses that elicited the best immune responses and found that this occurred at a total of 30 μg of antigen per fish. Subsequently, vaccination of fish with rHSP60, rENOLASE and rGAPDH achieved 46.9, 52 and 25% relative per cent survival (RPS), respectively. In addition, bivalent subunit vaccines – combination I (rHSP60 + rENOLASE), combination II (rENOLASE + rGAPDH) and combination III (rHSP60 + rGAPDH) – were administered and the RPS in these groups (65.6, 64.0 and 48.4%, respectively), was higher than that achieved with single‐antigen administration. Finally, in combination IV, the trivalent vaccine rHSP60 + rENOLASE + rGAPDH, the RPS was 1.6%. Taken together, our results suggest that combinations of two antigens may achieve a better efficiency than monovalent or trivalent antigens, and this may provide new insights into pathogen prevention strategies.  相似文献   

12.
Probiotics are currently being supplemented to cultured fish due to their benefits for fish performance. Herein, we tested the health protection and nutritional effects of probiotic Shewanella putrefaciens (Pdp11 strain), both fresh and lyophilized cells, on Senegalese sole (Solea senegalensis) juveniles. Pdp11 was incorporated into fish feed at concentration of 109 cells g?1, and then provided to juvenile sole for 2 months. Growth rates were significantly higher in fish fed the fresh probiotic compared with fish fed the control diet. Growth of fish receiving lyophilized bacteria was not improved when compared with controls. Body compositions (protein, total lipids and fatty acids profile) were similar for each dietary treatment. At the end of the study, fish were challenged by intraperitoneal inoculation with a pathogenic strain of Photobacterium damselae subsp. piscicida. Relative percentages of survival (RPS) ranged between 25% and 43.8% for fish receiving both probiotic supplemented diets. Both fresh and lyophilized Pdp11 cells conferred protection against P. damselae subsp. piscicida. However, only fresh Pdp11 enhanced Senegal sole performance. These findings should be taken into account for industry purposes in which lyophilized Pdp11 might be easier to manage.  相似文献   

13.
The antioxidant and oxidative damage responses and immune parameters in shrimp, Litopenaeus vannamei, reared in clear water (CW) and in a biofloc system (BFT) were evaluated. The animals were given feed supplemented with either nanocapsules containing the antioxidant lipoic acid (NCLA) or empty nanocapsules (NC). Antioxidant and oxidative stress analyses were evaluated by measuring glutathione S‐transferase activity (GST), reduced glutathione (GSH) concentration and lipid peroxidation (TBARS) in the gills, hepatopancreas and muscle. The immune parameters were then determined by the differential hemocyte count in the haemolymph. The final weight of the shrimp reared in both CW and BFT and treated with NCLA increased (p < .05). The shrimps reared in BFT showed increased GST activity in the gills and hepatopancreas after NCLA treatment (p < .05). Higher GSH levels were observed in the hepatopancreas with NCLA supplementation in CW and BFT (p < .05). Decreased levels of TBARS were observed in the gills and muscles of shrimp supplemented with NCLA and maintained in CW (p < .05). A decrease in the percentage of hyaline hemocytes and an increase in granular hemocytes were observed in shrimp treated with NCLA in CW and BFT (p < .05). The antioxidant treatment induced positive responses in terms of the zootechnical, biochemical and immunological parameters.  相似文献   

14.
The aims of this study were to unravel the intestinal microbiota of Litopenaeus vannamei after being fed a diet without (control) or with the synbiotic (SYN) for 60 days using next‐generation sequencing technology to see if changes in the intestinal microbiota were involved in the improved growth performance and health status of the shrimp. Next‐generation sequencing data showed that six phyla, 11 classes, 19 orders, 30 families, 58 genera and 73 species with taxonomic names assigned were detected. The majority of the operational taxonomic units (OTUs) was shared between the SYN and control shrimp and comprised 37 OTUs. However, intestinal biodiversity analyses revealed that SYN‐fed shrimp had a higher species richness, evenness and Shannon–Weaver index than did shrimp fed the control diet, but without reaching statistical significance. Interestingly, shrimp fed the SYN diet exhibited improved colonization of Lactobacillus plantarum and reduced prevalences of Vibrio harveyi and Photobacterium damselae in the intestines. These findings indicate that the SYN was able to modulate the intestinal bacterial community of shrimp and could be used to control vibriosis in shrimp.  相似文献   

15.
Photobacteriosis, caused by Photobacterium damselae subsp. piscicida (Phdp), is a serious disease in marine fish species worldwide. To date, the epidemiological characterization of this pathogen in Taiwan remains limited. In this study, we collected 39 Phdp isolates obtained from different farmed fish for phenotypic and genotypic analysis. Phenotype bioassays using API-20E and API-20NE systems showed that the Phdp is a homogeneous group. However, genotyping using the pulsed-field gel electrophoresis (PFGE) technique revealed genetic variability among Phdp isolates when 13 and 11 different PFGE band patterns were obtained with SmaI and NotI as restriction enzymes, respectively. Phylogenetic analysis using 16S rDNA and the Fur gene clustered Taiwanese isolates and other species of P. damselae in the same clade. In contrast, the ToxR phylogenetic tree, a powerful discriminatory marker, separated the two subspecies. Furthermore, the virulence-associated genes, AIP56, P55, PDP_0080, Sod and Irp1, were detected from all isolates. Virulence testing with nine representative isolates in cobia (Rachycentron canadum) and Asian sea bass (Lates calcarifer) showed that some were highly pathogenic with 80%–100% mortality rates. This study provides epidemiological data of Phdp infections in farmed fish in Taiwan, which is necessary to develop comprehensive prevention and control strategies for the disease.  相似文献   

16.
This study investigated the effects of the use of the inclusion of açaí on the diet of shrimp Litopenaeus vannamei on antioxidant and histopathological responses after exposure to ammonia. The shrimps were fed two experimental diets: control and with 10% of açaí inclusion (W/W), for 35 days. Afterwards, the organisms were exposed at four concentrations of ammonia (0.01‐control; 0.26; 0.48 and 0.91 mg NH3‐N L?1) for 96 hr. The total antioxidant capacity (ACAP) of the gills decreased significantly in both diets when exposed to ammonia, whereas in the muscle, the açaí promoted an increase in ACAP. Concomitantly, lipid peroxidation levels increased in the gills and decreased in muscle. After exposure to ammonia, glutathione‐S‐transferase activity increased in hepatopancreas in shrimps fed with açaí facilitating the detoxification of lipid peroxidation by‐products, and the concentration of protein sulfhydryl groups decreased in the gills and muscle of the shrimp of the control diet, evidencing protein damage, an unobserved response in shrimps that received the açaí diet. Histopathological changes decreased in açaí‐fed shrimps about the control diet after exposure to ammonia. It is concluded that açaí mitigated ammonia‐induced histopathological changes, improved the antioxidant defence system (gills and muscle) and attenuated the lipid damage in the muscle.  相似文献   

17.
李忠帅  马甡  单洪伟  王腾  肖威 《水产学报》2021,45(11):1825-1834
为探究亚硝态氮胁迫下凡纳滨对虾[体长为(6.8±0.3) cm,体质量为(4.0±0.6) g]体内亚硝态氮的时空分布与能量代谢相关酶活性的响应,实验设置0(对照组)、0.8、4.0和8.0 mmol/L 4个处理组,进行持续96 h的亚硝态氮胁迫实验和12 h的恢复实验。结果显示,凡纳滨对虾死亡率与胁迫浓度呈现显著的正相关性。胁迫6 h内,亚硝态氮在凡纳滨对虾鳃、血淋巴、肠道、肝胰腺和肌肉组织中明显积累,且积累量与胁迫浓度呈现正相关。相同胁迫浓度组,亚硝态氮在对虾鳃中积累最多,肌肉中最少,鳃中的积累量约为肌肉的3倍。Na~+-K~+-ATP酶活性在0.8和4.0 mmol/L组对虾肝胰腺和肌肉中显著升高,而在8.0 mmol/L组的肌肉中显著降低。胁迫各组对虾肝胰腺AMPK活性显著上升,且与胁迫浓度呈现正相关性。恢复期间,除血淋巴(8.0 mmol/L组)外,各组织中亚硝态氮1 h恢复效率均超过50%,且肝胰腺和鳃的恢复效率最高,达到74%以上。血淋巴、鳃、肠道中亚硝态氮恢复到对照组水平的时间最短,均在6 h以内,而水体中亚硝态氮含量显著升高。以上研究表明,胁迫下亚硝态氮会在对虾组织中迅速积累,并引起能量代谢进程的加快;胁迫解除后,积累在体内的亚硝态氮能够迅速排出体外,以减轻毒性影响。本研究结果将为缓解亚硝态氮对养殖对虾毒性效应的研究提供参考。  相似文献   

18.
2013年浙江省舟山市某网箱养殖条石鲷(Oplegnathus fasciatus)暴发了一种严重的疾病,病鱼主要症状为脾、肾出现1-2 mm的白色类结节.从患病鱼内脏处分离得到1株优势菌OF-1,经人工感染实验证实为此次引起条石鲷死亡的致病菌,半数致死量为5.93×104 CFU/g.形态学观察结果显示,菌株OF-1为革兰氏阴性、短杆状,在TCBS培养基上不生长.API 20E细菌鉴定系统、16S rRNA系统发育树分析结果证实,该菌株为美人鱼发光杆菌杀鱼亚种(Photobacterium damselae subsp.piscicida).该菌对庆大霉素、青霉素、氟哌酸、氧氟沙星、氨苄青霉素等药物高度敏感,对红霉素、链霉素、卡那霉素、苯唑青霉素等药物具有抗性.  相似文献   

19.
为系统解析凡纳滨对虾白便综合征 (white feces syndrome,WFS)的发生与环境因子、微生物因子、宿主免疫力和水体微生物群落组成的关系。实验利用水体理化因子、可培养细菌、对虾机体免疫酶活性以及高通量测序等检测技术对健康与患WFS的池塘养殖凡纳滨对虾进行比较分析。结果显示,与健康组相比,患病池塘的水温、溶解氧 (DO)、pH、盐度等水质理化因子波动趋势相似,波动范围分别为26.1~29.0 °C、4.26~6.08 mg/L、8.39~8.73和40~49,患病组DO和盐度比健康组高;健康组对虾肝胰腺内可培养细菌和弧菌含量为1.19×105~7.70×105和8.8×103~1.96×104 CFU/g,弧菌占比为2%~16%,患病组对虾肝胰腺内可培养细菌和弧菌含量在3.80×105~2.51×106和2.02×105~1.49×106 CFU/g范围内,比健康组高15~113倍,弧菌占比在55%~70%。碱性磷酸酶 (AKP)、酸性磷酸酶 (ACP)、溶菌酶 (LZM)、超氧化物歧化酶 (SOD)和酚氧化酶 (PO)活性在健康组内为1.21~5.64、9.17~15.25、3.56~7.43、4.83~6.70及3.10~4.55 U/mg,在患病组内为2.12~5.39、19.22~26.96、19.73~26.85、3.00~4.14及7.76~9.21 U/mg。比较分析表明,WFS的发生与可培养细菌含量、弧菌占比、ACP、LZM、PO的相关性较强。高通量测序分析表明,患病组水体菌群结构的Ace和Chao指数呈一定程度下降趋势,PCoA指数偏离度较高,放线菌门、变形菌门相对丰度降低,拟杆菌门、蓝藻门相对丰度显著升高;RDA关联分析表明,盐度、溶解氧、虾体细菌、虾体弧菌、水体细菌是影响患病对虾水体菌群结构组成的重要因子。相关研究结果为解析养殖生产中对虾WFS发生机制提供数据支撑,并为WFS的临床防控奠定理论基础。  相似文献   

20.
White spot syndrome virus (WSSV) has caused significant losses in shrimp farms worldwide. Between 2004 and 2006, Pacific white shrimp Litopenaeus vannamei (Boone) were collected from 220 farms in Taiwan to determine the prevalence and impact of WSSV infection on the shrimp farm industry. Polymerase chain reaction (PCR) analysis detected WSSV in shrimp from 26% of farms. Juvenile shrimp farms had the highest infection levels (38%; 19/50 farms) and brooder shrimp farms had the lowest (5%; one of 20 farms). The average extent of infection at each farm was as follows for WSSV‐positive farms: post‐larvae farms, 71%; juvenile farms, 61%; subadult farms, 62%; adult farms, 49%; and brooder farms, 40%. Characteristic white spots, hypertrophied nuclei and basophilic viral inclusion bodies were found in the epithelia of gills and tail fans, appendages, cephalothorax and hepatopancreas, and virions of WSSV were observed. Of shrimp that had WSSV lesions, 100% had lesions on the cephalothorax, 96% in gills and tail fans, 91% on appendages and 17% in the hepatopancreas. WSSV was also detected in copepoda and crustaceans from the shrimp farms. Sequence comparison using the pms146 gene fragment of WSSV showed that isolates from the farms had 99.7–100% nucleotide sequence identity with four strains in the GenBank database – China ( AF332093 ), Taiwan ( AF440570 and U50923 ) and Thailand ( AF369029 ). This is the first broad study of WSSV infection in L. vannamei in Taiwan.  相似文献   

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