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Biomedical subjects

K Pedersen

Publications and source records attributed to K Pedersen.

At least 73 records · Page 4Linked to original sources
PubMed1997

Immunological reactivity of Vibrio anguillarum sero-subgroups O2a and O2b, and comparison of their lipopolysaccharide profiles.

One hundred and twenty-nine Vibrio anguillarum serogroup O2 strains were compared by slide agglutination and Western blotting for their lipopolysaccharide (LPS) structure. The strains showed six different LPS profiles, four different reaction patterns in Western blotting, and four different kinds of reaction in slide agglutination, when both unabsorbed and absorbed anti-O2a and anti-O2b sera were used. All in all, nine different groups were detected when the combination of these three methods was applied. The two serological methods gave corresponding results for almost all strains (96%). Most of these strains (84%) belonged to sero-subgroup O2a, while 12% of the strains belonged to sero-subgroup O2b. The remaining six strains had varying reactions in the used serological methods; therefore, their sero-subgroups could not be determined. These results suggest the existence of additional sero-subgroups within serogroup O2.

Immune Sera↗
PubMed1997

Typing of the fish pathogen Listonella (Vibrio) anguillara by pyrolysis mass spectrometry.

Twenty-eight representatives of Listonella (Vibrio) anguillara serovars O1, O2 and O3 were compared by Curie-point pyrolysis mass spectrometry (PyMS). The representatives of serovars O1 and O3 formed discrete, homogeneous groups in ordination plots of the PyMS data. Strains from serovar O2 were recovered in two groups, one of which encompassed six strains including the type strain of the species and the reference strain for serovar O2, and the other included two strains which showed cross-reactions between serovars O2 and O5. The almost complete agreement found between the PyMS and the serological data suggests that pyrolysis mass spectrometry will prove to be an effective method for interstrain comparison within the species Listonella anguillara.

Animals↗
PubMed1997

Pathogenicity of Vibrio anguillarum serogroup O1 strains compared to plasmids, outer membrane protein profiles and siderophore production.

The virulence of 18 strains of Vibrio anguillarum serogroup O1 was compared to plasmid content, expression of siderophores and outer membrane proteins. All strains, irrespective of plasmid content, produced siderophores and inducible outer membrane proteins under iron-limited conditions. Only strains that carried the 67 kbp virulence plasmid or derivatives of it produced the outer membrane protein, OM2. All virulent strains harboured the 67 kbp plasmid or derivatives of it, indicating its importance for virulence. However, some strains carrying the virulence plasmid or a derivative of it, produced siderophores as well as OM2 but were non-pathogenic to fish. Likewise, among the virulent strains, considerable variation in LD50 values was recorded. Plasmid profiling and restriction analysis showed that the virulence plasmid existed in various molecular weights from 26 to 80 kbp, with 65-67 kbp being the most common, and that this plasmid displayed various restriction profiles. The presence of other plasmids did not seem to affect the pathogenic properties.

Animals↗
PubMed1997

Phenotypic and genotypic characterization of Vibrio vulnificus: proposal for the substitution of the subspecific taxon biotype for serovar.

The classification of Vibrio vulnificus strains into two biotypes has been maintained on the basis of phenotypic properties and eel virulence. Biotype 2 is virulent for eels, negative for the indole reaction, and serologically homogeneous (serogroup E), whereas strains of biotype 1 are avirulent, indole positive, and serologically heterogeneous. In the present study, we phenotypically and genotypically characterized 21 V. vulnificus isolates, recovered mainly from northern Europe, by comparing them with reference strains of both biotypes to look for new isolates of biotype 2. The results of this work revealed that the majority of isolates virulent for eels presented phenotypic traits previously considered characteristics of biotype 2 and specific ribotypes with HindIII. However, among the new isolates we found (i) a serogroup E strain virulent for eels but indole positive and (ii) one isolate not belonging to serogroup E but pathogenic for eels. Since no biochemical test for specific serogroup can with certainty be associated with eel virulence, we propose to classify V. vulnificus strains into serovars instead of biotypes. Thus, we suggest serovar E as the denomination of those strains previously classified as biotype 2. Finally, the occurrence of serogroup E in eels cultured in Norway and Sweden, as well as from human infections and shrimp, has been demonstrated.

Bacterial Typing Techniques↗
PubMed1997

Vibrio damsela associated with diseased fish in Denmark.

A total of 26 Vibrio damsela strains were isolated in Denmark. Fifteen strains were isolated from the head kidney of rainbow trout (Oncorhynchus mykiss) in aquaculture, eight were from organs of two stingrays (Dasyatis pastinaca) held in captivity, two were from organs and pathological material of a nurse shark (Orectolobus ornatus) held in captivity, and one was from the water in the aquarium where the rays and shark were kept. This is the first report on the isolation of V. damsela in Denmark and the first report on this organism associated with diseased farmed rainbow trout. Ecological and epizootiological aspects of the observation are discussed on the basis of phenotypic and genotypic properties of the isolated strains.

Animals↗
PubMed1997

Evidence of ancient life at 207 m depth in a granitic aquifer.

The results of electron-microscopy investigations of calcite precipitated in a water-conducting fracture in a ca. 1800 Ma granitic rock from 207 m below sea level at the island of Aspo on the southeastern (Baltic) coast of Sweden are compared with measurements of carbon, oxygen, and sulfur isotope composition of the calcite and embedded pyrite. Parts of the calcite had extremely low delta 13C values, indicative of biological activity, and contained bacteria-like microfossils occurring in colonies and as typical biofllms. X-ray microanalysis demonstrated these fossils to be enriched in carbon. Our results provide evidence for ancient life in deep granitic rock aquifers and suggest that the modern microbial life found there is intrinsic. Modeling historical and present geochemical processes in deep granitic aquifers should, therefore, preferably include biologically catalyzed reactions. The results also suggest that the search for life on other planets, e.g., Mars, should include subsurface material.

Calcium Carbonate↗
PubMed1997

Occurrence and identification of microorganisms in compacted clay-based buffer material designed for use in a nuclear fuel waste disposal vault.

A full-scale nuclear fuel waste disposal container experiment was carried out 240 m below ground in an underground granitic rock research laboratory in Canada. An electric heater was surrounded by buffer material composed of sand and bentonite clay and provided heat equivalent to what is anticipated in a Canadian nuclear fuel waste repository. During the experiment, the heat caused a mass transport of water and moisture content gradients developed in the buffer ranging from 13% closest to the heater to 23% at the rock wall of the deposition hole. Upon decommissioning after 2.5 years, microorganisms could be cultured from all samples having a moisture content above 15% but not from samples with a moisture content below 15%. Heterotrophic aerobic and anaerobic bacteria were found in numbers ranging from 10(1) to 10(6) cells/g dry weight buffer. Approximately 10(2), or less, sulphate-reducing bacteria and methanogens per gram of dry weight buffer were also found. Identification of buffer population members was performed using Analytical Profile Index (API) strips for isolated bacteria and 16S rRNA gene sequencing for in situ samples. A total of 79 isolates from five buffer layers were identified with API strips as representing the beta, gamma and delta groups of Proteobacteria and Gram-positive bacteria. Sixty-seven 16S rRNA clones that were obtained from three buffer layers were classified into 21 clone groups representing alpha and gamma groups of Proteobacteria, Gram-positive bacteria, and a yeast. Approximately 20% of the population comprised Gram-positive bacteria. Members of the genera Amycolatopsis, Bacillus, and Nocardia predominated. Among Gram-negative bacteria, the genera Acinetobacter and Pseudomonas predominated. Analysis of lipid biomarker signatures and in situ leucine uptake demonstrated that the buffer population was viable. The results suggest that a nuclear fuel waste buffer will be populated by active microorganisms only if the moisture content is above a value where free water is available for active life.

Aluminum Silicates↗
PubMed1997

Antisense RNA-regulated programmed cell death.

Eubacterial plasmids and chromosomes encode multiple killer genes belonging to the hok gene family. The plasmid-encoded killer genes mediate plasmid stabilization by killing plasmid-free cells. This review describes the genetics, molecular biology, and evolution of the hok gene family. The complicated antisense RNA-regulated control-loop that regulates posttranscriptional and postsegregational activation of killer mRNA translation in plasmid-free cells is described in detail. Nucleotide covariations in the mRNAs reveal metastable stem-loop structures that are formed at the mRNA 5' ends in the nascent transcripts. The metastable structures prevent translation and antisense RNA binding during transcription. Coupled nucleotide covariations provide evidence for a phylogenetically conserved mRNA folding pathway that involves sequential dynamic RNA rearrangements. Our analyses have elucidated an intricate mechanism by which translation of an antisense RNA-regulated mRNA can be conditionally activated. The complex phylogenetic relationships of the plasmid- and chromosome-encoded systems are also presented and discussed.

Apoptosis↗
PubMed1997

Vibrio anguillarum serogroup O3 and V. anguillarum-like serogroup O3 cross-reactive species--comparison and characterization.

Forty-five Vibrio anguillarum-like isolates reacting with V. anguillarum serogroup O3 antiserum were examined in 30 characters to clarify their phenotypical properties, while their genotype was examined by ribotyping. The strains were isolated from diseased and dead fish or from environmental sources such as water, sediment, plankton, and faeces and gills of healthy fish. Phenotypically, the similarity of all the strains was more than 90%. However, significant differences between the fish-associated and environmental strains were detected. Biochemically, deviations were found in the Voges-Proskauer test and lysine decarboxylase reaction. Clustering analysis of the ribotypes showed two distinct clusters with a similarity of only 32%. Two strains representing each of these groups were used in a LD50 study, which showed some difference also in the pathogenicity between environmental and fish strains. It is suggested that the environmental strains belong to another species than V. anguillarum, but serologically cross-reacting with the V. anguillarum serogroup O3. The ribotyping as well as biochemical results indicated that the environmental strains possibly belong to Vibrio aestuarianus. The bona fide V. anguillarum serogroup O3 strains proved to be very homogeneous both phenotypically and genotypically, and the similarity of ribotypes was more than 96%. The V. anguillarum-like, serogroup O3-reactive strains from the environment were more heterogeneous in their biochemical behaviour, and showed an approximately 70% similarity in ribotypes.

Antigens, Bacterial↗
PubMed1997

Vaccination strategies in freshwater salmonid aquaculture.

The focus of this chapter is antibacterial vaccines. The main salmonid species in freshwater aquaculture is the rainbow trout. Other salmonid species are produced on a limited scale. The most important bacterial fish diseases in European freshwater aquaculture are the rainbow trout fry syndrome-RTFS-(Flavobacterium psychrophilum) and enteric redmouth disease-ERM-(Yersinia ruckeri) which are widespread and cause serious epizootics, while furunculosis (Aeromonas salmonicida) is endemic, only giving overt disease under extremely stressing conditions. In the hatchery, there is a need for vaccination against RTFS (not commercially available) and ERM; in the ponds it is urgent to vaccinate against ERM, while the importance of furunculosis vaccination is not clear. The fish for ongrowing in saltwater should be vaccinated against ERM, furunculosis and vibriosis. Commercial vaccines are available against these diseases, either as single component or combination vaccines for immersion and injection-and oral vaccines are under registration. Hitherto, there has not been much strategic research on vaccination in freshwater; however recent results suggest that with the regime of vaccines available (and soon available), fish should be vaccinated with an ERM immersion vaccine in the hatchery approximately four weeks before transfer to the ponds. To cover the growth period in fresh water an oral booster should be given two to three months later. There is a need for development and research in strategic use of an RTFS and a furunculosis vaccine in freshwater aquaculture.

Aeromonas↗
PubMed1997

Viability during storage and stability of plasmids during storage and subculturing in strains of Vibrio anguillarum.

The stability of plasmids, 3.3 kb - approximately 200 kb, in 8 strains of Vibrio anguillarum displaying different plasmid profiles and reactions with O-antisera was investigated over an 18 months period. All plasmid profiles proved to be resistant to storage at different temperatures but strains stored at 37 degrees C were only viable for a short period of maximum 2 months. Strains stored at 5 degrees C and 20 degrees C were viable for a longer period. Viable strains maintained their plasmid profile throughout the experiment, except in 2 cases where a 67 kb and a 200 kb plasmid were lost. Strains stored at -80 degrees C all remained viable and maintained their plasmid profile throughout the study. By subcultivating daily for up to 100 successive days, most strains maintained their plasmid profiles. Only 2 strains lost their plasmid. When picking 100 single colonies from agar plates, none of the colonies showed plasmid profiles deviating from the expected. The results suggest that plasmid profiles among V. anguillarium are very stable during subculturing, storage and laboratory handling using standard laboratory procedures, and thus, reliable for epidemiological investigations. In a second experiment, 2 pairs of 2 strains were grown together in mixed cultures. They were identical in all traits, except that one strain in each pair harboured the 67 kb pJM1-like virulence plasmid, whereas the other had lost this plasmid. The result showed that the growth rate was the same for strains with and without the plasmid, indicating that under laboratory conditions, this plasmid is neither a benefit nor the opposite for bacterial growth.

Animals↗
PubMed1996

Restriction fragment length polymorphism of the pMJ101-like plasmid and ribotyping in the fish pathogen Vibrio ordalii.

A total of 32 Vibrio ordalii strains were studied for their plasmid content and shown to carry a plasmid of approximately 32 kb. This plasmid was subsequently subjected to restriction fragment length polymorphism (RFLP) studies. Using Hind III, three different restriction patterns were identified while BamH I cleaved the plasmid into a single linear fragment. The results suggest that the 32 kb plasmid is highly conserved but that some variation in restriction pattern occurs. The same set of strains was subjected to ribotyping. Using Mlu I, six different restriction patterns were demonstrated. Strains from the USA and Canada shared profiles with strains from Australia and Japan. Strains from Australia generated a single pattern whereas strains from North America were subdivided into three patterns, and the Japanese strains fell into five patterns. The results suggest that ribotyping in combination with RFLP studies of the pMJ101-like plasmid may be useful in epidemiological studies of V. ordalii.

Animals↗
PubMed1996

Plasmid profiles, restriction fragment length polymorphisms and O-serotypes among Vibrio anguillarum isolates.

A total of 279 Vibrio anguillarum strains were serotyped and examined for plasmid content. Plasmids were subjected to digestion with restriction enzymes. Most strains belonged to serogroup O1 (39%) and O2 (16%). In total 164 strains (53%) carried plasmids. Of the O1 and O2 isolates, 92% and 30%, respectively, carried one or more plasmids. Restriction fragment length polymorphism (RFLP) analysis of plasmid DNA indicated that plasmids belonged to several groups. Each group seemed to be restricted to a single O-serovar. The largest group was the pJM1-like plasmids among most serovar O1 strains. Most of these plasmids were about 67 kb like the pJM1 plasmid, but various derivatives ranged from 26-77 kb. RFLP studies of the 67 kb plasmids revealed 17 different restriction patterns. Some patterns were dominant among European strains whereas others were dominant among North American strains. The results confirmed the applicability of O-serotyping together with plasmid profile and restriction analysis of plasmids for typing of V. anguillarum. They also indicated that plasmids among strains which belonged to the traditional fish pathogenic serogroups, O1 and O2, showed more homology than did strains from most other serogroups, that were usually non-pathogenic, environmental bacteria.

Plasmids↗