ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00822.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.A total of eight reference strains and 43 environmental isolates ofVibriospecies that are potential fish pathogens, were assayed for the production and utilization of siderophores. Chemical and biological assays indicated that all species produced phenolate compounds and only some strains ofV. choleraenon‐O1,V. parahaemolyticusandV. fluvialisproduced hydroxamates. Bioassays indicated that all species produced compounds that stimulated the growth of the homologous and the heterologous species in low‐iron media. The catechol‐type siderophores produced may be functionally related to enterobactin as demonstrated by bioassays with enterobactin‐deficient mutants. However, the chromatographic analysis and absorption spectra of supernatants and their extracts showed some differences among catechols excreted byVibrio species.The hydroxamate compounds produced by some strains ofV. fluvialisandV. parahaemolyticuswere different from the aerobactin. The synthesis of iron‐regulated outer membrane proteins was also examined in representative strains of each species. The molecular size of the main induced proteins ranged between 74 and 95kDa, and were relatively species

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00823.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Aeromonas salmonicidaproduces many extracellular enzymes, some of which are known to play an important role in pathogenesis and virulence, while the role of others is presently speculative. The latter group includes amylase, aryl‐sulphatase, glucosidases, esterases and lysophospholipase. There are two enzymes which are known to be of prime importance in pathogenesis: a 70‐kDa protease (caseinase) and a 25‐kDa phospholipase (glycerophospholipid: cholesterol acyltransferase, GCAT). The protease causes extensive tissue liquefaction, activates the blood clotting system and is lethal for fish at 2·4 μg/g fish. It is inhibited by α2‐macroglobulin but resistant to all the other serum protease inhibitors. Its rolein vivoappears to be as a broad spectrum protease providing amino acids forin vivogrowth. The GCAT is mainly present in a high molecular weight complex with LPS. The complex is extremely haemolytic for fish (but not mammalian) erythrocytes. It is the most lethal component of the exotoxins (lethal dose 45 ng/g fish). The complex with LPS confers enhanced toxicity to the GCAT and stability to heat and proteolytic degradation.In vitro, this toxin also has high leucocytolytic and cytolytic (RTG‐2) activity. On injection into fish, it causes very little histopathology other than a marked degranulation of eosinophilic granular cells (EGCs) in the gills. Its precise mode of pathogenesis is uncertain and appears complex. The protease and the GCAT/LPS have an additive relationship in respect to lethal doses and mixtures of the two produce extensive liquefactive and haemorrhagic lesions typical of furuncles. The possible relationship of the GCAT/LPS to other less well characterized factors (cytotoxin, leucocytolysin, haemolysin, salmolysin)

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00824.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Columnaris disease,Flexibacter columnarisinfection, was first described in North America. Recent publications indicate that its distribution is worldwide. Both warmwater and coldwater fish are infected withF. columnaris.All freshwater fish are probably susceptible to the disease under environmental conditions favourable to the bacterium and stressful to the fish.Flexibacter columnariscannot tolerate sea water. Generally, outbreaks occur when the average water temperatures reach 15°C. The bacterium apparently enters the fish through the skin and gills. The swarms of bacteria involved give the lesions a characteristic yellow pigmentation. The external lesions destroy the skin, muscle and gill tissues. It is relatively easy to isolate the bacteria from the internal organs of the diseased fish, but there is no evidence of internal tissue damage. In this short review, emphasis is placed on several factors relative to water environment which play a role in the development of outbreaks of columnaris disease:1The optimum temperature for an outbreak ofF. columnarisinfection is thought to be between 20 and 30°C. Mortalities seldom occur at temperatures below 15°C, although highly virulent strains can kill fish at lower temperatures.2Flexibacter columnariscan survive longer in water of normal to high hardness, as well as in water containing small amounts of sodium, potassium, calcium or magnesium salts, but it cannot live in sea water.3Flexibacter columnarisgrows well on paniculate fish feeds so that such deposits in the water may act as reservoirs of infection.4An important source of infection is feral fish. In the Columbia River or the Fraser River, resident coarse fish such as suckers,Catostomusspp., are thought to transmit the infection to returning adult salmon.5Flexibacter columnarisfails to invade fish in the presence of competitive bacteria likeCitrobacter freundiiwhen its initial numbers are approximately one in a 100 less than those of the competitors.6Crowding seems to be not only a stressor for fish, but also a factor that increases the chance of adhesion ofF. columnaristo the external tissues of fi

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00825.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Selected salmonid fish farms in England and Wales were sent a questionnaire designed to collect data on enteric redmouth disease (ERM) vaccination and the usage of antimicrobial agents. The response to the survey was 41·5%. The results indicated that 22% of responding farms have had ERM diagnosed since 1982, half of them have experienced the disease every year since the initial confirmation and it occurs primarily between April and September; mainly in rainbow trout,Oncorhynchus mykiss(Walbaum), of 222/kg‐200g. Although larger fish were also affceted. The incidence of ERM coincides with a rise or fall in water temperature, over‐crowding, poor water quality or grading. Vaccination against ERM is used on 53% of the responding farms. In addition, 45% of these farms considered immunization to have failed, mainly due to the poor condition of the fish and the low water temperatures at vaccination. On those farms whieh employed vaccination, the commonest ehemotherapeutant used against ERM is oxolinic acid. However, oxytetracycline is the most frequently used antibiotic on farms not employing a vaccine. The use of an antimicrobial agent as a prophylactic or the use of another compound when the first treatment is completed occurred on some farms. The average annual cost for vaccination and treatment has been calcul

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00826.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Two haemolysin genes (AHH4 and AHH‐2) ofAeromonas hydrophilaATCC7966 were cloned into a plasmid vector inEscherichia coliK‐12. An open reading frame (ORF) of the AHH‐1 haemolysin gene was 1734 base pairs (bp). and corresponded to a protein of 577 amino acid residues. Analysis of the deduced amino sequence indicated a highly hydrophobic N‐terminal region which had the characteristics of a leader peptide. The sequence also included the ‐10 region and the ‐35 region of a promoter, and a ribosome‐ binding site upstream from the ORF. The termination site was located downstream from the ORF. The haemolysin was a thermolabile protein with the predicted molecular mass of 60 kDa. The AHH‐1 gene is distributed in variousA. hydrophilaandA. salmonicidastrains. The nucleotide sequence of a 981 bp ORF of the AHH‐2 gene was encoded with the predicted molecular mass of 377 kDa polypeptides. The homology of the nucleotide sequence was very low between the AHH‐1 and AHH‐2 genes, and also with the aerolysin gene cloned by Howard&Buckley (19S6). No leader peptide was found in the N‐terminal region of the ORF of the AHH2 gene. The AHH‐2 gene was detected in the original strain ATCC7966, but was not detected in other tested strains ofA. hy

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00827.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Twenty‐fiveAeromonas hydrophilastrains, isolated from freshwater fish and from freshwater samples were identified, using API 20NE and CH50. They were screened for the one plasmid (20 kb), and a third group (four strains) contained two or three plasmids. A 20 kb plasmid was common to all plasmid‐positive strains. Although their plasmid profile differs, all groups are very similar with regard to their biochemical and physiological characterization. However, the differences observed using clustering can be explained by characteristics, some of which have been reported as virulence associated. No relationship between these factors and the presence of plasmids is found. The possibility of differentiating A. hydrophila strains on the basis of biochemical characteristics using a cluster analysis is conside

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00828.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Aeromonas salmonicidawas studied at fish farms producing salmonid smolts in northern and central Finland from 1982 onwards.Aeromonas salmonicidasubsp.salmonicidahas been causing epizootics in salmon,Salmo salarL., and trout,S. truttaL., 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 atypicalA. salmonicidaproved 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 atypicalA‐salmonicidacaused mortality among brown trout at one farm in northern Finland and one in centra

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00829.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.The degree of resistance to an atypical strain ofAeromonas salmonicida, the causative bacterium of carp erythrodermatitis, was examined in two strains of carp,Cyprinus carpioL.: a Polish line. R3, sixth generation of conventional inbreeding (full‐sib matings); and a Hungarian line. R8, fifth generation of conventional inbreeding. Comparisons were made between and within the two strains. Results showed a significant difference (P<0·001) in the degree of resistance, with the Hungarian carp showing greater resistance than the Polish carp. Differences within each strain were also observed indicating a maternal influence on resistance. Two transferrin genotypes in three genetic combinations were identified (DD, DG, GG) but were not found to influence resistan

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00830.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.The efficacy of florfenicol against laboratory‐induced infection withAeromonas salmonicidawas tested in Atlantic salmon,Salmo salarL., parr. Medication at three dose levels in the feed was started 24 h after bath challenge withA. salmonicida.The specific mortality rate in the unprotected infected control group was 75% compared with 5, 13 and 17% when florfenicol was given at dose levels of 20, 10 and 5 mg per kg body weight per day, respectively. Florfenicol was palatable to the fish at doses in excess of effective therapeutic levels and feeding for 10 days at 100 mg per kg, or for prolonged periods at 50 mg per kg and 10 mg per kg, resulted in no feeding problems or histopathological abnormalities. Florfenicol appears to have a good therapeutic index and considerable potential in the control of furunculosis in salmo

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00831.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY