The potential of bacteriophage therapy to control bacterial disease in farmed fish was tested using, as an example, furunculosis of Atlantic salmon, caused by Aeromonas salmonicida subsp. salmonicida.
In vivo testing with Atlantic salmon and rainbow trout (Oncorhynchus mykiss Walbaum) showed no adverse effects, with bacteriophage generally cleared within 96 h of administration by either intraperitoneal (i.p.) injection or oral in-feed.
Juvenile Atlantic salmon were administered a combination of bacteriophage O, R and B (1.9 × 108 pfu fish− 1) by i.p. injection, after they had been challenged with A. salmonicida subsp. salmonicida 78027, also by i.p. injection. The fish that were injected with bacteriophage immediately after challenge died at a significantly slower rate then those that were either not treated with bacteriophage, or treated 24 h post-challenge. However, the end result (100% mortality) was not affected.
In further experiments the effects of oral (1.88 × 105 pfu g− 1 fish− 1 daily for 30 days), bath (1.04 × 105 ml− 1 daily for 30 days) and i.p. (6.25 × 107 pfu fish− 1) phage treatment to control furunculosis in experimentally infected Atlantic salmon were compared with antibiotherapy (treatment with 10 mg kg− 1 bw− 1 day− 1 oxolinic acid for 10 days), using an indirect cohabitation challenge. No protection was offered by any of the bacteriophage treatments, compared to the positive challenge group, although significant protection was offered by the oxolinic acid treatment. Analysis of samples taken from the trials demonstrated that bacteriophage were correctly administered to the fish and, on occasion, were isolated from fish that had succumbed to furunculosis. It was also shown that bacteriophage resistant A. salmonicida subsp. salmonicida isolates could be recovered from mortalities in all the treatment groups.
The results suggest that, although there were no safety problems associated with the approach, furunculosis in Atlantic salmon is not readily controllable by application of bacteriophage. 相似文献
Atlantic salmon were fed 40, 300 or 1100 mgall-rac--tocopheryl acetate kg feed–1 for 12 weeks.After 6 weeks half of the fish in each group were marked and vaccinated (i.p.injection) against furunculosis and vibriosis. Liver -tocopherol levelsreflected the dietary input after 6 and 12 weeks of feeding. Noimmunomodulatoryeffects of dietary vitamin E on baseline levels of the immune parameters beforevaccination were detected in this study, as evaluated by antibody dependent andspontaneous plasma complement activities. In general, vaccination increasedplasma complement activities and the number of antigen specific antibodyproducing cells as compared with unvaccinated control fish, but with nodifferences with respect to the vitamin E regimes. Also the ability ofunvaccinated fish to withstand experimental furunculosis was unaffected bydietary vitamin E. The concentrations of -tocopherol and ascorbic acidinthe liver were, however, negatively affected 6 weeks post vaccination comparedto respective unvaccinated fish. 相似文献
Aeromonas salmonicida subsp. salmonicida is a fish pathogen. Analysis of its genomic characteristics is required to determine the worldwide distribution of the various populations of this bacterium. Genomic alignments between the 01-B526 pathogenic strain and the A449 reference strain have revealed a 51-kb chromosomal insertion in 01-B526. This insertion (AsaGEI1a) has been identified as a new genomic island (GEI) bearing prophage genes. PCR assays were used to detect this GEI in a collection of 139 A. salmonicida subsp. salmonicida isolates. Three forms of this GEI (AsaGEI1a, AsaGEI1b, AsaGEI2a) are now known based on this analysis and the sequencing of the genomes of seven additional isolates. A new prophage (prophage 3) associated with AsaGEI2a was also discovered. Each GEI appeared to be strongly associated with a specific geographic region. AsaGEI1a and AsaGEI2a were exclusively found in North American isolates, except for one European isolate bearing AsaGEI2a. The majority of the isolates bearing AsaGEI1b or no GEI were from Europe. Prophage 3 has also a particular geographic distribution and was found only in North American isolates. We demonstrated that A. salmonicida subsp. salmonicida possesses unsuspected elements of genomic heterogeneity that could be used as indicators to determine the geographic origins of isolates of this bacterium. 相似文献
A genetically attenuated strain of Aeromonas salmonicida has been developed that has a complete deletion of the aroA gene (Brivax II), making it suitable for development as a commercial vaccine. Brivax II was effectively cleared from Atlantic salmon, Salmo salar, a species highly susceptible to furunculosis, confirming that it is attenuated. Clearance rate was dependent on the vaccine dose administered, being longer with higher doses. Immunological studies using Brivax II injected in rainbow trout, Oncorhynchus mykiss, confirmed that live vaccines stimulate a greater response, in terms of generating leucocytes able to proliferate to a subsequent encounter with antigen, relative to killed vaccines. Development of strains of Brivax II as carriers of heterologous antigens was also investigated. Escherichia coli -galactosidase was chosen as the model antigen, and three strains containing plasmids with the LacZ gene were constructed (Brivax 12, Brivax 61 and Brivax 107). All three strains were shown to express -galactosidase in vivo in rainbow trout and to be cleared effectively. Interestingly, Brivax 107 was cleared faster than the other two Lac+ strains and had the highest level of -galactosidase activity. The two strains expressing lower levels of activity also behaved differently in vivo, in that Brivax 12 accumulated derivatives expressing lower levels of -galactosidase activity, suggesting that mutants are being selected in vivo. The potential advantages of live vaccines over killed vaccines are discussed. 相似文献