Biomedical subjects

J L Barja

Publications and source records attributed to J L Barja.

48 records · Page 3Linked to original sources

PubMed1988

Inhibitory activity of antibiotic-producing marine bacteria against fish pathogens.

The activity of antibiotic-producing marine bacteria was assayed against bacterial fish pathogens belonging to the genera Vibrio, Aeromonas, Pasteurella, Edwardsiella, Yersinia and Pseudomonas with the aim of evaluating the possible use of these marine strains for controlling epizootics in aquaculture. Inhibition tests on solid medium showed that, in general, the majority of fish bacteria were strongly sensitive to the marine bacteria. Only two strains (Edwardsiella tarda and Pseudomonas aeruginosa), were resistant to all the antibiotic-producing strains. The results of antagonism assays in sea water, however, varied according to the fish pathogens examined. Experiments conducted using cell-free supernatant fluids of marine bacteria demonstrated the involvement of antibiotic substances in the inhibition of fish pathogens.

Animals↗

PubMed1988

Virulence properties and enterotoxin production of Aeromonas strains isolated from fish.

The biological activities in vivo and in vitro of 59 motile Aeromonas spp. isolated from fish and water tanks were simultaneously analyzed in poikilothermic and homoiothermic systems. A total of 64.3% of the isolates tested were pathogenic for fish, and 62% of Aeromonas hydrophila and A. sobria isolates either virulent or nonvirulent for fish were enterotoxigenic. Although the majority of the strains were proteolytic and amylolytic and produced DNase, other activities, such as elastase and staphylolysis, were only present in A. hydrophila. Most of the strains (96%) produced hemolysins, and 68% had agglutinating capacity, but neither isolates pathogenic for fish nor enterotoxigenic isolates showed specificity for trout or human erythrocytes, respectively. The production of siderophores, agglutination in acriflavine, and precipitation after boiling were found not to be useful tests for screening virulent strains. Although statistical analysis revealed a significant relationship between virulence for fish and positive results for arabinose and sucrose fermentations, elastase, and hemolysis of human erythrocytes, only lysine decarboxylase showed a significant positive relationship with enterotoxigenicity. Using extracellular products from representative Aeromonas strains with different virulence markers and belonging to distinct O serogroups, we demonstrated a lack of correlation between cytotoxicity for fish and homoiothermic cell lines and pathogenicity. The extracellular products from selected pathogenic A. hydrophila strains were lethal for rainbow trout and displayed proteolytic, hemolytic, and cytotoxic activities which were simultaneously lost after heat treatment. The findings reported here indicate that it is not possible to establish a common and single mechanism involved in the invasion of Aeromonas spp. in poikilothermic and homoiothermic hosts.

Aeromonas↗

PubMed1988

Chromosome-mediated iron uptake system in pathogenic strains of Vibrio anguillarum.

We describe in this work a new iron uptake system encoded by chromosomal genes in pathogenic strains of Vibrio anguillarum. This iron uptake system differs from the plasmid-encoded anguibactin-mediated system present in certain strains of V. anguillarum in several properties. The siderophore anguibactin is not utilized as an external siderophore, and although characteristic outer membrane proteins are synthesized under iron-limiting conditions, these are not related to the plasmid-mediated outer membrane protein OM2 associated with ferric anguibactin transport. Furthermore, the siderophore produced by the plasmidless strains may be functionally related to enterobactin as demonstrated by bioassays with enterobactin-deficient mutants, although its behavior under various chemical treatments suggested major differences from that siderophore. Hybridization experiments suggested that the V. anguillarum chromosome-mediated iron uptake system is unrelated genetically to either the anguibactin or enterobactin-associated iron assimilation systems.

Animals↗

PubMed1986

Evaluation of different assay systems for identification of environmental Aeromonas strains.

Important biochemical reactions in conventional tests were compared with counterpart reactions in two multiple test systems, API-20E (Analytab Products, Plainview, N.Y.) and Aeromonas hydrophila medium, to evaluate their accuracy for the identification of motile Aeromonas spp. isolated from fish. In a total of 49 Aeromonas spp. isolates and 10 A. hydrophila reference strains, false-negative or -positive reactions were detected in the Voges-Proskauer test, indole production, gelatinase activity, production of gas, fermentation of arabinose, and lysine decarboxylase reaction. A good correlation was found, among the three identification systems, for the fermentation of mannitol and inositol as well as for the arginine dihydrolase and ornithine decarboxylase tests. The failure of A. hydrophila medium in the detection of gas indicates that this medium is not entirely suitable for defining aerogenic or anaerogenic strains. From the results of the present study, we consider that of the identification method and taxonomic scheme to be adopted for environmental Aeromonas spp. must be standardized.

Journal Article↗

PubMed1985

Plasmids mediating iron uptake in Vibrio anguillarum strains isolated from turbot in Spain.

Vibrio strains isolated from diseased turbot in an experimental fish farm on the Atlantic coast of northwest Spain were identified as Vibrio anguillarum. The isolates shared many biochemical characteristics with V. anguillarum strains obtained from other sources, and harboured a plasmid species that showed extensive homology with plasmid pJM1, carried by V. anguillarum strain 775 isolated from an epizootic in North America. Restriction endonuclease analysis showed that the two plasmids were very similar albeit not identical. The presence of the plasmid in the turbot isolates was associated with their ability to cause disease in fish. Plasmid-carrying bacteria could also grow under conditions of iron limitation. Two outer membrane proteins, of 86 and 79 kDal, were induced, and a similar siderophore activity to that produced by V. anguillarum 775 was also detected under these conditions. The 86 kDal outer membrane protein cross-reacted immunologically with antiserum raised against the outer membrane protein OM2 produced by strain 775. Nonvirulent plasmidless derivatives were unable to grow under iron-limiting conditions, and were also unable to produce either siderophore activity or the 86 kDal outer membrane protein, suggesting the plasmid-mediated nature of these components.

Animals↗

PubMed1985

Modified medium for the oxidation-fermentation test in the identification of marine bacteria.

Using the medium of ZoBell as a basal formulation, we developed a medium to determine the oxidative-fermentative metabolism in marine bacteria. Different oxidative and fermentative collection strains, as well as a group of unidentified marine bacteria, were tested on modified ZoBell medium and other conventional media. In general, superior results were obtained with the modified ZoBell medium since it supported good bacterial growth and gave more clear-cut oxidative reactions.

Journal Article↗

PubMed1984

Plasmid coding for transferable drug resistance in bacteria isolated from cultured rainbow trout.

The occurrence of drug resistance and plasmid-mediated transferability was investigated in 170 strains belonging to eight bacterial groups isolated from cultured rainbow trout. It was found that 87.6% of the strains were resistant to at least one drug, with the highest percentages of resistance being detected for ampicillin (54.7%), sulfadiazine (46.5%), nitrofurantoin (38.2%), and chloramphenicol (37.0%). Six enterobacteria, two Vibrio, and one Aeromonas isolate transferred resistance factors to Escherichia coli K-12. The most common transmissible R factor determined resistance to chloramphenicol and sulfadiazine, demonstrating an association between a specific plasmid and the resistance pattern transferred. The presence of chloramphenicol in fish food was detected by bioassay. In general, transfer frequencies were similar in primary and secondary matings, which indicate the potential water-borne dissemination of these R plasmids.

Animals↗

PubMed1983

Characterization of plasmids in bacterial fish pathogen.

Plasmid profiles of representative fish pathogens, Aeromonas salmonicida, Aeromonas hydrophila, Vibrio anguillarum, Pasteurella piscicida, Yersinia ruckeri, Edwardsiella tarda, and Renibacterium salmoninarum, were determined by agarose gel electrophoresis with four different plasmid detection methods. A combination of two methods was required to detect the plasmids present in these strains and to calculate precisely the molecular weights of the plasmids. Of 38 strains, 28 harbored one or more plasmids, with the majority of strains demonstrating multiplasmid banding. Similarity in plasmid banding between strains was noted and related to geographic source. Five strains of A. salmonicida possessed six plasmid bands having molecular weights of 8.6 X 10(6), 8.4 X 10(6), 8.1 X 10(6), 3.6 X 10(6), 3.5 X 10(6), and 3.4 X 10(6). Four P. piscicida isolates shared three plasmid bands having molecular weights of 37 X 10(6), 15 X 10(6), and 5 X 10(6), and five A. hydrophila strains harbored a common plasmid having a molecular weight of ca. 20 X 10(6) to 30 X 10(6). The highest-molecular-weight plasmids (145 X 10(6) and 130 X 10(6) were detected in V. anguillarum. From curing experiments, it was found that in A. hydrophila strain 79-62, a loss of resistance to tetracycline was associated with loss of plasmid content in all susceptible derivatives, suggesting plasmid-mediated tetracycline resistance. Cell surface characteristics and metabolic properties were also modified in cured derivatives of A. hydrophila strain 79-62.

Aeromonas↗

PubMed1983

Molecular factors associated with virulence of marine vibrios isolated from striped bass in Chesapeake Bay.

On the basis of cultural and biochemical properties as well as DNA homology assays, 81 Vibrio strains isolated from diseased striped bass and from Chesapeake Bay water were assigned to eight distinct groups. All organisms belonging to two of the groups were pathogenic for striped bass and were identified as Vibrio anguillarum, whereas organisms classified in the other six groups were nonpathogenic and were designated as Vibrio spp. Unlike the pathogenic V. anguillarum strain 775 isolated in the Pacific Northwest, strains pathogenic for striped bass did not contain any plasmids; however, they were similar to the Northwest isolates in that virulence was correlated with their ability to grow in the presence of nonimmune striped bass serum or under conditions of iron limitation. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of outer membranes showed that additional proteins were induced in those organisms capable of growth under conditions of iron limitation. It was of interest that 22 of the nonpathogenic isolates harbored one or more plasmids which, by restriction endonuclease analyses, were shown to be clearly different from the virulence plasmid pJM1.

Animals↗

PubMed1983

Mechanism of poliovirus inactivation by cell-free filtrates of marine bacteria.

The mechanism of enterovirus inactivation by marine bacteria was investigated using poliovirus type 1 as a model virus and with strains of Pseudomonas and Vibrio isolated from the marine environment. Treatment of virus with cell-free filtrates from late log phase bacterial cultures produced alterations in the viral capsid as shown by a reduction in efficiency of adsorption to host cells, increased sensitivity to ribonuclease, and by the release of ribonucleic acid from the treated virions. Filtration of 14C-labelled, treated virus through 25-nm filters revealed that the majority of the isotope (85-96%) passed the filters, indicating extensive capsid disruption. However, the most rapid and pronounced change observed during virus inactivation was the loss of infectivity, suggesting that enzymatic degradation is not the first event in the poliovirus inactivation process by marine bacteria.

Adsorption↗

PubMed1982

Antiviral activity of antibiotic-producing marine bacteria.

The stability of poliovirus 1 in estuarine water and sediment was examined. The present data indicated that a 2 log reduction in virus titer at 15 degrees c occurred within 6-7 days in water samples taken from estuarine waters on both sides of the Atlantic Ocean. The antiviral effect decreased significantly when the seawater was subjected to autoclaving but not when it was filtered. That the antiviral activity activity of the seawater was related to the growth activities of microorganisms was corroborated by the isolation of antibiotic-producing marine bacteria that had marked activity against poliovirus (net inactivation greater than or equal to 2 logs within 6-8 days). These organisms retained this activity following repeated subcultivation on laboratory media. Since comparable inactivation rates were observed in cell-free filtrates from these marine strains, extracellular products appear to be involved in the virus-inactivation process. Other enteric viruses, Coxsackie B-5 and ECHO-6, were also inactivated by these marine bacteria. The addition of sediment to natural seawater increased the length of poliovirus survival more than three times over that in seawater alone. However, this was not found under sterile conditions, suggesting that the sediment can protect the viruses from inactivation by the marine microflora.

Anti-Bacterial Agents↗

PubMedDate not supplied

Electrotransformation of Yersinia ruckeri by plasmid DNA.

Yersinia ruckeri, a fish pathogenic bacterium in aquaculture, was used to evaluate the electroporation as a new transformation method for this species. DNA used for the electrotransformation were plasmids of molecular mass ranging from 2.3 kb to 33 kb, and diverse replicons. To optimize this method we used Y. ruckeri 11.29 strain (from serotype 02) and pSU2718 DNA. The best transformation efficiency (6.0 x 10(5) transformants/micrograms DNA) was obtained with 12.5 kV/cm, 25 microF, 400 omega and 2 hours of incubation after pulse. When these conditions were applied to other strains belonging to different serotypes and other plasmids, we obtained transformants in all strains assayed, but only when using low molecular weight plasmids. Plasmid vectors and resident plasmid were not modified in host strains after electrotransformation. In studies of conformation we confirmed that only circular DNA was able for transformation. The utilization of this technique for direct cloning in Y. ruckeri makes possible further studies on recombinant DNA.

Cell Division↗