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1.
Abstract. The survival of Aeromonas salmonicida subsp. salmonicida was investigated in sea water under a variety of conditions. Survival in different types of microcosms (glass or dialysis bags); of bacteria grown under both in vivo and in vitro (broth culture) conditions; and in sterile and non-sterile sea water were compared. In all cases, survival was found to be of short duration (<10 days) and did not conflict with the previously stated obligate nature of the pathogen. The spread of furunculosis may depend less on its ability to survive in the environment than on its rate of shedding from infected fish and prevailing hydrographic conditions. Survival was extended and growth occurred in sterile sea water to which nutrients (tryptone soya broth) had been added. However, sea water obtained from beneath a commercial salmon cage, which would have been expected to be nutrient rich, did not prolong the survival of the pathogen. In vivo infectivity studies provided no evidence for the existence of unculturable but infective forms of A. salmonicida subsp. salmonicida which, therefore, validates the use of colony-forming units as a measure of survival. 相似文献
2.
E.-M. BERNOTH 《Journal of fish diseases》1991,14(3):419-422
Abstract. A method is described which improves both the specificity and paracticability of immune identification of Aeromonas salmonicida. The modified assay employs antisera raised against outer membrane proteins (OMP) of A. salmonicida cells and is carried out as a dot blot test on nitrocellulose membranes. Performance of the test with 55 non- A. salmonicida bacterial isolates from fish and water revealed weak cross reactivity in five cases. However, these cross reactive only occur at very high antigen concentrations and can be overcome by adequate dilution. 相似文献
3.
Four non-pigment-producing isolates and two pigment-producing isolates of Aeromonas salmonicida sp. salmonicida were isolated from the head-kidney of diseased farmed Atlantic salmon, Salmo salar L. The cultural, morphological and biochemical features of the isolates were compared with those of reference strains. Injection and cohabitation experiments were performed. The only difference between the non-pigment-producing isolates and the pigment producing reference strains of A. salmonicida ssp. salmonicida was the inability of the former to produce pigment. In the injection experiments, the investigated non-pigment-producing isolate produced a significantly higher mortality compared with the mortality caused by the reference strain, whereas no difference in mortality was detected in the cohabitation experiments. 相似文献
4.
Plasma samples obtained from rainbow trout either experimentally infected with Aeromonas salmonicida or injected with either A. salmonicida lipopolysaccharide (LPS) or a commercial A. salmonicida vaccine (Lipogen) were analysed by enzyme immunoassay to evaluate changes in rainbow trout ladderlectin (RTLL) concentrations during the acute phase response (APR). Plasma RTLL concentrations in fish injected with A. salmonicida LPS, vaccine or live A. salmonicida varied over a 10 day period, but did not significantly increase. In contrast, fish experimentally infected with A. salmonicida exhibited a modest, but statistically significant ( P < 0.05), decrease in RTLL concentration. These studies demonstrate that RTLL is not detectably induced during the trout APR to sterile inflammation or A. salmonicida infection, but plasma concentration of this protein may be reduced during bacterial infection. 相似文献
5.
Abstract. A method using 1-MDS electropositive filters for the concentration of Aeromonas salmonicida from hatchery water was developed. The procedure consisted of passing hatchery water at ambient pH through the filters followed by the elution of the adsorbed bacteria in a small volume of 3% beef extract solution (pH 10.0). A 300-fold reduction in volume of hatchery water and an average recovery of 35% of the seeded bacteria was achieved. 相似文献
6.
Abstract. The infectivity of the bacterial fish pathogen Aeromonas salmonicida subsp. salmonicida to Atlantic salmon, Salmo salar L., in sea water was investigated and found to be similar to that reported for fresh water. The minimal infective dose in short duration bath exposures (1–3 days) was 104 colony-forming units (cfu) per ml, while prolonged exposure for three weeks, but not for 1 week, produced infection with 102 cfu/ml. Intragastric intubation of A. salmonicida established infection with doses of >105 cfu. Release of bacteria from dead or morbid infected fish was monitored and found to be in the order of 105 –108 cfu/fish/h. These results emphasize the importance of removing dead fish from farm sites. 相似文献
7.
Abstract. Aeromonas salmonicida ssp, salmonicida is shown to produce several extracellular proteins having gelatinolytic activity. Among the six isolates tested, two (NCMB 1102 and 84–14–R) produced both high (89–100 kDa) and low molecular (37 kDa) weight gelatinases, while the other four demonstrated only the 89–100 kDa forms. The low molecular form (metalloprotease 1: MP 1, 37 kDa) was isolated by ammonium sulphate precipitation, hydrophobic, ion exchange and size exclusion chromatography. The isolated enzyme was inhibited by the metal-chelating agents o-phenantroline and EDTA, and by excess Zn ions, and thus was defined as a metalloprotease. Its pH-optimum was 7–5, optimal activity was at 40°C and its pI 5.2. Specificity studies demonstrated cleavage of gelatin and azocoll, but not casein. 相似文献
8.
Abstract. The fate of the fish pathogen Aeromonas salmonicida in the marine environment was examined by culture, epifluorcscence microscopy, the indirect fluorescent antibody technique (1FAT), direct viable counts (= Kogure technique) and the assessment of respiratory activity by the reduction of tetrazolium compounds to coloured formazans. In laboratory- based systems containing sediment, water, algae and invertebrates, cells of A. salmonicida were observed microscopically after plate counts on tryptone soya agar declined to zero. Survival was maximal at a salinity of 25%o , and in wood and sediment, notably mud, rather than the water column. 相似文献
9.
Abstract. Eighty isolates of Aeromonas salmonicida , recovered from separate outbreaks of furunculosis in farmed and wild salmon in Scotland during 1988 and 1989, were examined for susceptibility to the β-lactam antibiotic amoxycillin. Susceptibility was determined in terms of minimum inhibitory concentration (MIC). All of the A. salmonicida subsp. salmonicida isolates investigated were susceptible to amoxycillin, with MICs of 0.30–1.50mg1-1 . All of the A. salmonicida subsp. achromogenes isolates tested were resistant to amoxycillin, with MICs in excess of 500mgl-1 . The A. salmonicida subsp. achromogenes produced a β-lactamase enzyme with a pI of approximately 8.0. The enzyme was inducible and its production was unaffected by plasmid curing with ethidium bromide, suggesting that resistance was chromosomal rather than plasmid mediated. 相似文献
10.
To determine the dynamics of the transmission of Aeromonas salmonicida ssp. salmonicida infection, chinook salmon, Oncorhynchus tshawytscha, were exposed to bacteria by cohabitation. The latent period (time between exposure and infectivity) was determined by exposing a group of chinook salmonid fingerlings to A. salmonicida by bath, then, at daily intervals, by holding five exposed (donor) fish with approximately 50 naive fish for 24 h. The latent period was 3 days post-infection and the time period between the initial exposure to bacteria and the beginning of bacterial shedding was 4.5 days for the same animals. The prevalence and intensity of infection in the donor fish, to which recipient fish were exposed, i.e. the level of exposure, was highly correlated with the development of disease in recipient (susceptible) chinook salmon (r2 = 0.57). An experiment was conducted to determine the daily progress of infection and development of a furunculosis epidemic among recipient fish by cohabiting a single exposed fish with 43 unexposed salmon. At daily intervals, all fish (in seven treatment tanks and one control tank daily) were sacrificed and tested for the presence of A. salmonicida in the kidney (n = 3520). Over 10 days, mean prevalence among recipient fish reached 75% and disease related mortality exceeded 50%. Bacterial concentrations in the water continued to increase over the duration of the experiment in concert with the number of infected animals present in the population. 相似文献
11.
The aerobiological (aerosol) pathway of Aeromonas salmonicida subspecies salmonicida (ATCC 33658) was investigated. Results indicate that viable A. salmonicida can travel as an aerosol/droplet spray at least 104.1 cm (limits of the test chamber used) when carried by air currents. Additionally, viable A. salmonicida was recovered from water exposed to an experimentally generated aerosol/droplet spray of A. salmonicida downwind from the contaminant source. It is possible that viable bacterial aquatic animal pathogens can be spread via the airborne route. This possible route of pathogen introduction could effect current management or system designs, especially when aquaculture systems consist of tanks in close proximity. 相似文献
12.
Aeromonas salmonicida in Finland: pathological problems associated with atypical and typical strains 总被引：3，自引：0，他引：3
Abstract. Aeromonas salmonicida was studied at fish farms producing salmonid smolts in northern and central Finland from 1982 onwards. Aeromonas salmonicida subsp. salmonicida has been causing epizootics in salmon, Salmo salar L., and trout, S. trutta L., at two coastal farms in northern Finland sinee 1986, involving 1–29% mortality in the fish-rearing units affceted. The disease causes more serious losses of sea trout yearlings and brood fish than of salmon. The achromogenic atypical A. salmonicida proved to be the most common bacterial disease in brown and sea trout at one farm in northern Finland throughout the period, causing constant heavy losses, mainly of fingerlings, especially in 1982–1986. It was found only occasionally in central Finland. Pigment-producing atypical A- salmonicida caused mortality among brown trout at one farm in northern Finland and one in central Finland. 相似文献
13.
Abstract. The histopathology of an atypical Aeromonas salmonicida found in Atlantic cod, Gadus morhua L., is described. Unlike members of the Salmonidae, the cod showed a well-developed host reaction to A. salmonicida involving encystment of the bacteria. When Atlantic salmon, Salmo salar L., were given an intramuscular injection with suspensions of cultures of this strain of A. salmonicida no cellular host reaction was observed. When cod were given a similar injection the bacteria showed degenerative changes, leucocytes accumulated, and cyst formation was seen in the spleen and kidney. Since cod can be infected by this organism the possibility exists that they could act as carriers, a source of infection for salmonids in saltwater cage culture or in the wild. 相似文献
14.
Abstract. Oxolinic acid and two new fluoroquinolones, ciprofloxacin and norfloxacin, were evaluated for in vitro antibacterial activity against Aeromonas salmonicida. Although oxolinic acid was as active as ciprofloxacin in terms of minimum inhibitory concentration (MIC), fluoroquinolones were significantly more active in terms of their ability to kill both oxolinic acid sensitive and resistant strains of A. salmonicida. Furthermore, the fluorinated drugs were active against non-dividing A. salmonicida. It would appear worthwhile to carry out further investigations with fluoroquinolones as they may be more effective in treating A. salmonicida infections than the current regime of oxolinic acid. 相似文献
15.
裸盖鱼(Anoplopoma fimbria)是一种名贵的冷水经济鱼类,已在我国北方地区开展小规模的工厂化繁育和养成.目前,我国关于裸盖鱼的病害研究仍是空白.本研究对山东烟台一养殖场自然发生疥疮病的裸盖鱼进行了病原分析,从发病鱼体内分离得到形态一致的优势菌株,命名为AF-1,并对其进行了致病性检测、菌种鉴定及药物敏感性研究.人工感染实验证明,AF-1对裸盖鱼有致病性,呈现症状与自然发病状态一致;结合形态观察、革兰氏染色、生理生化特征、16S rRNA和gyrB基因序列进化树分析,将AF-1鉴定为杀鲑气单胞菌(Aeromonas salmonicida);药物敏感性实验结果显示,AF-1对青霉素、阿莫西林、头孢噻吩等13种抗生素具有耐药性,对氟苯尼考、氟甲喹等16种抗生素敏感.综上所述,本研究首次报道了我国养殖裸盖鱼感染杀鲑气单胞菌病例,为裸盖鱼养殖过程中的疾病防控和疫苗开发提供了参考. 相似文献
16.
Jørgen B Lødemel Terry M Mayhew Reidar Myklebust Rolf E Olsen Sigrun Espelid & Einar Ringø 《Aquaculture Research》2001,32(12):935-945
Arctic charr ( Salvelinus alpinus L.) were fed diets based on a commercial recipe supplemented with either linseed, soybean or marine oil prior to cohabitant challenge with Aeromonas salmonicida ssp. s almonicida . Mortality varied significantly between the three dietary groups. Highest mortality (48%) was observed in fish fed the marine oil and the lowest mortality (20%) was in the group fed soybean oil. Transmission electron microscopy (TEM) examination of the digestive tract of uninfected fish demonstrated substantial numbers of bacterial cells between microvilli. However, only a few bacteria were recovered that were associated with the microvilli of infected fish. Immunocytochemical staining/labelling investigations using TEM and an immunogold method were performed on mid-gut segments of fish fed the marine oil diet and showed augmentation of goblet cells and the presence of A. salmonicida ssp. salmonicida in the gastrointestinal tract of diseased fish after challenge with the pathogen. It is suggested that the gastrointestinal tract could be an infection route of A. salmonicida ssp. salmonicida. The greater prevalence of goblet cells supports the suggestion that sloughing off mucus is a protective response against bacterial infections. These results make an important contribution to our understanding of how nutrition can affect the disease resistance of fish. 相似文献
17.
D. K. SAKAI 《Journal of fish diseases》1987,10(3):171-179
Abstract. The transformation of Aeromonas salmonicida with DNA fragments from bacterial cell-free sonicates was investigated with intraspecific, interspecific band intergeneric fish pathogenic bacteria including Aeromonas salmonicida, Aeromonas hydrophila, Pseiidomonas fluorescens and Vibrio anguillarum strains as donor bacteria. A phenotypic marker for transformation was extracellular protease production since a protease-deficient mutant NTG-1 induced from pathogenic A. salmonicida strain A-7301 by mutagenesis was used as a recipient. This mutant was non-pathogenic to rainbow trout. The mutant was incubated with each sonicate at 20°C for 20 days with a nutrient-poor medium containing a trace (5 μg/ml each) of both humic acid and tryptone in the presence of clean river sand (100 g/100 ml medium) corresponding with an environment of rivers. During the incubation, the survival of mutant NTG-1 cells was observed and protease positive NTG-1 cells were isolated from each culture. The protease production of the isolates was due to the transmission of protease genes of the donor strains. The activity of proteases produced by the transformants extra-cellularly was determined. These transformants induced with the sonicates of the parent strain, intraspecific strain and with the sonicates of the interspecific A. hydrophila strain were pathogenic to rainbow trout, whereas the transformants derived with the sonicates of the intergeneric strains P. fluorescens and V. anguiUarum showed non-pathogenicity, although all the donor strains, with the exception of the P. fluorescens strain, were pathogenic. These findings are interesting since they demonstrate that trausformation in A. salmonicida occurs with considerable ease even intergenencally and interspecifically, as well as intraspecifically in river environments, and that there is a large difference in the lethal toxicity of extracellular protease produced by these bacteria. 相似文献
18.
Two extracellular metalloproteases were purified from a culture filtrate derived from Aeromonas salmonicida ssp. salmonicida . One enzyme, leucine aminopeptidase (LAP), which had a molecular mass 37 kDa, hydrolysed aminoterminal l -leucine and l -phenylalanine. The activity was inhibited by 1,10-o-phenanthroline, but not by EDTA. The addition of excess Zn2+ to an o-phenanthroline-inhibited enzyme restored most of its activity. The peptidase was temperature stable, and had an optimum temperature and pH of 60 °C and 8, respectively. The other enzyme, metalloprotease 3 (MP3), which had a molecular mass 20 kDa, was an endoprotease, and hydrolysed azocoll and hide powder-azure, but not gelatine. The MP3 enzyme had an optimum temperature and pH of ≈40 °C and 7.5, respectively, and a cationic isoelectrical point. 相似文献
19.
Abstract. The indirect immunoperoxidase technique (IPT) was used to examine specific superficial colonies of organisms observed on the gills of salmonids. The evidence obtained suggested that the superficial colonies were not a form of Aeromonas salmonicida , the causative agent of furunculosis. Application of the IPT to bacterial smears and previously stained histological sections from a case of furunculosis, confirmed the sensitivity of the technique and suggested the presence of common antigens between A. salmonicida and members of the Vibrionaceae, Pseudomonaceae and Enterobacteriaceae. 相似文献
20.
Abstract. The ability of A-layer-positi ve (A+ ) and A-layer-negative (A− ) strains of Aeromonas salmonicida to utilize haem sources of iron under conditions of iron-restriction was evaluated. In a plate bioassay, only A+ strains of A. salmonicida were able to utilize haem from a variety of sources including haem, haemin, myoglobin, haemoglobin, haemoglobin- haptoglobin and haem-albumin complexes. Trypsin-digestion of whole cells abolished haem- binding, indicating that binding was cell-surface associated, involving a protein binding site or receptor. Competitive binding studies indicated that all haem compounds were bound by a common receptor, which was not iron-regulated and was associated with the presence of the 49-kDa A-layer protein. The ability of both typical A+ (siderophore-positive) and atypical A+ (siderophore-negative) strains to utilize haem indicated that the mechanism of haem utilization was not siderophore-mediated and that A. salmonicida possesses both siderophore-dependent and siderophore-independent mechanisms to overcome iron-restricted conditions encountered in vivo. 相似文献