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Six various motile Areromonas strains were evaluated with regard to their induction of agglutinin and precipitin production in the serum of immunised rabbits. The results were compared with immunogenic activities of the strains against MAS in carp. A total of 74 Aeromonas sp. strains were involved in carrying out agglutination and precipitation tests. No relationship between agglutinin production and the immunogenic properties of the strains used was determined. In contrast, strains inducing precipitin production against a wide antigen spectrum of non-homologous Aeromonas sp. strains demonstrated the highest immunogenic activity in carp. The immunity of carp derived from vaccinations with the antigens of certain motile Aeromonas strains effectively protected against both homologous and non-homologous strains from this group of microorganisms.
This report presents the data considered by the author as the most important reasons for difficulties in the diagnosis and control of MAS and MAI caused by motile Aeromonas bacteria in fish. The difficulties are chiefly attributed to the properties of these microorganisms, such as their wide variety and variability. Furthermore, numerous studies into certain aspects involved in the pathogenecity of motile Aeromonas in fish have been indicated; however, the comparison of the results of these studies is limited or impossible. The necessity of investigations which may improve diagnostic procedures as well as lead to more applicable, efficient and reasonable methods of the control of MAS and MAI has been stressed.
The relationship between the prevalence of normal serum agglutinins and precipitins to Aeromonas hydrophila and A. veronii biotype sobria in carp and the sensitivity of the fish to infection with these bacteria was studied. The presence of these antibodies depended on carp population and on individual fish. No correlation between the prevalence of agglutinins and the sensitivity of carp to infection was found. On the contrary, the fish having the precipitins to particular Aeromonas strains revealed significantly lower sensitivity to infections with the respective homologous strains than those without the precipitins.
The taxonomy and virulence of four unknown bacterial isolates (11S9306, 16S9306, 12E9306, 13E9306) associated with erytrodermatitis-like symptoms of carp have been examined. The isolates differed from currently known bacteria pathogenic for carp. Characteristics of the isolates were nearly identical with those of Chromobacterium violaceum. Differences concern indole production and d-mannitol utilization (isolates+, Ch. Violaceum -). In virulence tests (subcutaneous injection of 1x10⁷ cfu, and intraperitoneal injection of 5x10⁵ cfu) the isolates appeared to be more pathogenic than pathogenic strains of Aeromonas hydrophila and A. salmonicida var. achromogenes. This phenomenon was a little more pronounced at 21°C than at 13°C.
The aim of the study was to determine the relationship between serogroups, species, and virulence of Aeromonas sp. Isolates from common carp and rainbow trout were tested for species designation and virulence phenotype and then serogrouped. A total of 558 isolates were tested. The bacteria were identified to species level using PCR-RFLP method. The ß-haemolysin, gelatinase, and caseinase activities were selected for virulence determination. The following species were dominant: A. hydrophila (35), A. bestiarum (103), A. salmonicida (98), A. sobria (101), A. veronii bt. sobria (171), and A. encheleia (30). 380 isolates were classified as virulent for fish. The isolates were serogrouped by agglutination tests according to the scheme of Sakazaki and Shimada. 478 isolates were serologically typeable (they did not show R type antigen or autoagglutination) and for 419 (87.6%) O-antigen was identified. The dominant serogroups among both carp and trout isolates were: O:11, O:16, O:18, O:33, PGO1, and PGO2. Groups O:3, O:6, O:41, PGO4, and PGO6 dominated among carp isolates and groups O:21, O:29, PGO5, and PGO9 were only represented by trout isolates. The relationship between Aeromonas serogroups and species was not found. Of the 15 dominant serogroups, eight groups included only isolates with virulence phenotype and two groups included only non-pathogenic isolates. The remaining groups were represented by virulent, as well as non-virulent isolates. Agglutination test can be used as alternative or complementary method to differentiate pathogenic and non-pathogenic isolates from carp and trout cultured in Poland.
The present study compares the protective effect of two autologous vaccines against homologous and heterologous Yersinia ruckeri strains. These studies were preceded by determining optimal vaccination conditions (antigen dose and fish exposition time to the vaccine suspension). Each of the vaccines contained antigens prepared from one of two strains of Y. ruckeri: YR1 or Pt426, which originated from different farms and exhibited some biochemical differences. The fish were immersed in the vaccines containing 108 of antigens for 60 sec. (conditions determined as optimal). Six weeks after immunization, the fish that had been immunized with the different vaccines were divided into four groups. One of them was infected with the strain that is homologous to the vaccine. Each of the remaining groups was infected with one of the three heterologous strains. The relative percentage of survival (RPS) after infection with homologous strains was 90.5% for YR1 and 87% for Pt426, while for heterologous strains RPS it was markedly lower at a range of 33 to 67%. The results indicate that vaccines prepared using Y. ruckeri strains originating from particular farms and applied only in these farms may result in the best prophylaxis against yersiniosis in rainbow trout.
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The aim of the paper was to present the clinical data in four cases of flavobacteria infections in fish cultured in Poland and to characterize the isolates. The cases occurred in September 2005 and in February and March 2006 in three trout farms and one carp farm. In the first case, Fl. psychrophilum and Fl. columnare were isolated from apparently healthy rainbow trout. In the second case, common carp showed clinical signs specific for columnaris disease and abundant growth of bacteria producing yellow colonies was observed in skin and gills samples. The bacteria of separated isolates were identified as Fl. columnare. In the third case, abundant growth of flavobacteria was obtained from rainbow trout fry population with haemorrhages in the yolk sac and numerous mortalities. Separated isolates were identified as Fl. psychrophilum and Fl. branchiophilum. In the fourth case, skin darkening and mortalities were observed in rainbow trout after moving to another farm. An abundant growth of bacteria from kidney and intestine samples was obtained and yellow colonies grew uniformly or predominated over other bacterial flora. Fl. psychrophilum was identified among the isolates. In total, 17 isolates were identified. All the isolates showed characteristics specific for flavobacteria: they grew on Cytophaga agar, produced yellow colonies with spreading, wrinkled or whole edges (dependend on bacteria species). Cultures comprised Gram-negatie, long cells without spores or fruiting bodies (except for three isolates). Other phenotypic properties were consistent with those of reference strains used in the studies. The isolates identified as Fl. columnare, Fl. branchiophilum or Fl. psychrophilum varied little in their range of properties with regard to data of other authors.
The studies aimed to evaluate the effect of experimental Aeromonas hydrophila vaccine on the total number of leukocytes, the number of neutrophils and T-lymphocytes and the phagocytic activity of the neutrophils and monocytes of carp (Cyprinus carpio L). The vaccine was given intraperitoneally or in an 1-hour bath. The number of leukocytes and the phagocytic activity were examined several times during a 42-day period after immunisation. Examinations were conducted at 12°C and 23°C. A visible increase of the total number of leukocytes and T-lymphocytes (21 days after immunisation) and neutrophils (7 to 14 days after immunisation) was found at 12°C. The percentage of engulfing phagocytes and their activity were significantly higher than those in the controls during the whole experimental period. A marked decrease in the total number of leukocytes was seen as early as 14 days after immunisation at 23°C; moreover, the number of neutrophils and T-lymphocytes was significantly lower on day 21 post immunisation as compared to that in the controls. On the other hand, the phagocytic activity was visibly higher than that in control fish but differences were less marked than those at 12°C.
The aim of the study was to evaluate the influence of monovalent A.hydrophila and A. sobria vaccine on the induction of the protective immunity against the heterologous strains of Aeromonas genus in carp (C. carpio L.). Additionally, the level of immunity in carp after single and double vaccinations was compared. Separate groups of carp were immunised with 1S-95 (A.hydrophila) or 4R-96 (A.sobria) antigens by intrapesi to neal injection or by immersion. The immunisation efficiency was evaluated using challenge tests with various heterologous strains of Aeromonas genus. Carp revealed a partial immunity against the heterologous strains irrespective of the antigen kind and the route of vaccine administration. Fish immunised by immersion demonstrated a particularly high level of immunity. Antigen 1S-95 (A.hydrophila) protected more efficiently against another heterogenous strain of A.hydrophila than against A.sobria strain and vice versa. Double immunisation failed to increase the protective immunity as compared to that produced by a single immunisation.
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