Findings and measures to eradicate methicillin resistant Staphylococcus aureus clonal complex 7 spa-type t091 in two Norwegian pig farms: a case report.

BACKGROUND: The Norwegian LA-MRSA surveillance and control strategy in pig farms has been largely successful in preventing the establishment of MRSA in the pig population by identifying positive pig herds and eradicating MRSA from these. It can, however, be challenging to determine whether a particular type of MRSA is livestock-associated, particularly in cases where there is little evidence available to aid in classification. CASE PRESENTATION: In two Norwegian pig farms linked by trade of live pigs, MRSA CC7 t091 was found in samples from pigs and their environment. Longitudinal sampling, with a time interval of 25 days, in one farm demonstrated an increase in samples positive for MRSA CC7 t091, supporting a classification of the finding as livestock associated. Measures to eradicate MRSA from both farms were imposed by the National Food Safety Authority. Different measures of MRSA sanitation were applied in the two farms, and MRSA was successfully eradicated from both farms. CONCLUSIONS: A high-cost, labor intensive and a lower-cost, less labor intensive MRSA eradication protocol, both including total depopulation and repopulation were successful in eradicating MRSA CC7 t091 from two case farms.

Inferring Atlantic salmon post-smolt migration patterns using genetic assignment.

Understanding migratory patterns is important for predicting and mitigating unwanted consequences of environmental change or anthropogenic challenges on vulnerable species. Wild Atlantic salmon undergo challenging migrations between freshwater and marine environments, and the numbers of salmon returning to their natal rivers to reproduce have declined over several decades. Mortality from sea lice linked to fish farms within their seaward migration routes is proposed as a contributing factor to these declines. Here, we used 31 microsatellite markers to establish a genetic baseline for the main rivers in the Hardangerfjord, western Norway. Mixed stock analysis was used to assign Atlantic salmon post-smolts caught in trawls in 2013-2017 back to regional reporting units. Analyses demonstrated that individuals originating from rivers located in the inner region of the fjord arrived at the outer fjord later than individuals from middle and outer fjord rivers. Therefore, as post-smolts originating from inner rivers also have to migrate longer distances to exit the fjord, these data suggest that inner fjord populations are more likely to be at risk of mortality through aquaculture-produced sea lice, and other natural factors such as predation, than middle or outer fjord populations with earlier exit times and shorter journeys. These results will be used to calibrate models estimating mortality from sea lice on wild salmon for the regulation of the Norwegian aquaculture industry.

Effects of laboratory salmon louse infection on Arctic char osmoregulation, growth and survival.

High salmon lice (Lepeophtheirus salmonis) infestation levels resulting from intensive salmonid sea-cage aquaculture can threaten populations of wild salmonid hosts. This includes anadromous Arctic char (Salvelinus alpinus), which rely on short migrations into more productive seawater environments to build energy stores for maturation, spawning and over-wintering in freshwater. Elevated salmon lice burdens may limit the benefits of migration by constraining osmoregulation, growth, survival and reproduction. To test for these effects, we simulated anadromous migration in tanks by transferring individually tagged Arctic char smolts (n = 352, averaging 133 g) to seawater where they were infected with salmon lice or left as uninfected controls for 1 month, and then transferring them back to freshwater for 2 months. After the seawater phase, infected post-smolts had a mean of 0.33 (range of 0.09-0.91) mobile lice g-1 fish weight. At this point, specific growth rates (SGRs) dropped in infected compared to control fish (0.1% vs. 1.6% day-1). Higher plasma Na+ and osmolality in infected fish also indicate osmoregulatory impairment. Throughout the study, mortality was 18.2% and 1.7% in infected and control groups, but sexual maturation was low and comparable between groups. Infection intensity correlated positively with mortality rate and plasma Cl-, and correlated negatively with SGR and condition factor (CF). CF dropped (ΔCF < 0) at intensities of >0.09 lice g-1 fish weight, and intensities of >0.3 causing zero or negative SGRs and increased mortality were particularly concerning. If infection intensities reach these levels in the wild, char could be impacted by growth restrictions and increased mortality rates, which potentially cause shorter migration durations, lowered reproductive success and possibly also selection against anadromy. This study provides vital information for conservation practitioners wanting to understand the physiologically derived burden salmon lice can have on Arctic char populations, and can be used to define thresholds in the monitoring and conservation of Arctic char populations affected by aquaculture-driven salmon lice infestations.

Sea trout adapt their migratory behaviour in response to high salmon lice concentrations.

Sea trout face growth-mortality trade-offs when entering the sea to feed. Salmon lice epizootics resulting from aquaculture have shifted these trade-offs, as salmon lice might both increase mortality and reduce growth of sea trout. We studied mortality and behavioural adaptations of wild sea trout in a large-scale experiment with acoustic telemetry in an aquaculture intensive area that was fallowed (emptied of fish) synchronically biannually, creating large variations in salmon lice concentrations. We tagged 310 wild sea trout during 3 years, and gave half of the individuals a prophylaxis against further salmon lice infestation. There was no difference in survival among years or between treatments. In years of high infestation pressure, however, sea trout remained closer to the river outlet, used freshwater (FW) habitats for longer periods and returned earlier to the river than in the low infestation year. This indicates that sea trout adapt their migratory behaviour by actively choosing FW refuges from salmon lice to escape from immediate mortality risk. Nevertheless, simulations show that these adaptations can lead to lost growth opportunities. Reduced growth can increase long-term mortality of sea trout due to prolonged exposure to size-dependent predation risk, lead to lower fecundity and, ultimately, reduce the likelihood of sea migration.

Timecourse of oocyte development in saithe Pollachius virens.

Wild caught North Sea saithe Pollachius virens were monitored for growth, sex steroid profiles and oocyte development pre-spawning and measured for egg size and group fecundity during the spawning season in the laboratory. Vitellogenesis commenced in late October-early November, at a leading cohort size (CL ) of c. 250 µm, after which oocytes grew rapidly in size until spawning started in February. Notably, a distinct cortical alveoli stage was virtually absent with yolk granules observed in developing oocytes at the very beginning of vitellogenesis. Little atresia was observed pre-spawning, but atretic re-absorption of remnant oocytes containing yolk granules was found in all females immediately post-spawning. As expected, concentrations of sex steroids, oestradiol-17ß (females), testosterone (both sexes) and 11-ketotestosterone (both sexes), increased pre-spawning before dropping post-spawning. The present experiment provides the first validation of sex steroid levels in P. virens. Post-ovulatory follicles were visible in histological sections from female gonads 9-11 months post-spawning, but then disappeared. Spawning commenced around a CL of c. 750 µm (700-800 µm). Hydrated oocytes (eggs) measured between 1·04 and 1·31 mm (mean = 1·18 mm) with decreasing sizes towards the end of spawning. The average estimated realized fecundity was c. 0·84 million eggs (median female total length, LT = 60 cm). Spawning lasted from 13 February to 29 March.

Alterations in the Atlantic cod (Gadus morhua) hepatic thiol-proteome after methylmercury exposure.

Proteomic studies in general have demonstrated that the most effective and thorough analysis of biological samples requires subfractionation and/or enrichment prior to downstream processing. In the present study, Atlantic cod (Gadus morhua) liver samples were fractionated using activated thiol sepharose to isolate hepatic proteins containing free/reactive cysteines. This subset of proteins is of special interest when studying the physiological effects attributed to methylmercury (MeHg) exposure. Methylmercury is a persistent environmental contaminant that has a potent affinity toward thiol groups, and can directly bind proteins via available cysteine residues. Further, alterations in the cod thiol-proteome following MeHg exposure (2 mg/kg body weight) were explored with two-dimensional gel electrophoresis combined with downstream mass spectrometry analyses for protein identifications. Thirty-five protein spots were found to respond to MeHg exposure, and 13 of these were identified when searching cod-specific databases with acquired mass spectrometry data. Among the identified thiol-containing proteins, some are known to respond to MeHg treatment, including constituents of the cytoskeleton, and proteins involved in oxidative stress responses, protein synthesis, protein folding, and energy metabolism. Methylmercury also appeared to affect cod heme metabolism/turnover, producing significantly altered levels of hemoglobin and hemopexin in liver following metal exposure. The latter finding suggests that MeHg may also affect the hematological system in Atlantic cod.

Precision-cut liver slices of Atlantic cod (Gadus morhua): an in vitro system for studying the effects of environmental contaminants.

The Atlantic cod (Gadus morhua) is an economically important species commonly consumed by humans. The widespread distribution of cod in the North Atlantic Ocean makes it vulnerable to effluents from human activities, such as coastal industries and offshore petroleum exploration. It has been demonstrated that many effluents have adverse effects on cod reproduction and health, e.g. by disrupting endocrine signaling pathways. The liver, expressing important components of the biotransformation and the endocrine system, is one of the main target organs. Thus, reliable and reproducible in vitro systems of the liver are important for studying effects of environmental contaminants. The aim of this study was to investigate precision-cut liver slices (PCLS) as an alternative in vitro system for toxicological studies of the Atlantic cod liver. Slices of 8 mm in diameter and 250 µm thickness were prepared and cultivated from immature cod. Several analyses to measure the liver slice viability were performed: enzyme assays, histology, and morphometric analysis, all confirming cell viability for up to 72 h in culture. The liver slices were also exposed to two well-known model environmental contaminants, ß-naphthoflavone (BNF) and 17α-ethynylestradiol (EE2), representing established agonists for the aryl hydrocarbon receptor (AHR) and the estrogen receptor (ER), respectively. The results showed increased transcription of the target genes cytochrome P450 1A (CYP1A) and vitellogenin (VTG), both well-established biomarkers for exposure of fish to the selected compounds. In conclusion, PCLS is a promising in vitro system for toxicological studies of cod liver cells. The liver slices are viable in culture for several days and respond to environmental contaminants in a dose- and time-specific manner.

The effect of dietary lipid content and stress on egg quality in farmed Atlantic cod Gadus morhua.

The present study assessed differences in fecundity and egg quality from Atlantic cod Gadus morhua fed isoproteic diets containing 13% fat (low fat, LF) or 20% fat (high fat, HF) and either stressed or left unstressed as a control over the spawning season. Each diet was fed to triplicate groups of G. morhua from June 2009, through to first maturation and spawning. In January 2010 sub-groups of G. morhua were moved to land-based spawning tanks where the experimental trial was carried out. At the start of the experiment, G. morhua fed the high-fat diet were significantly larger than G. morhua fed low-fat diet. These differences were maintained through the spawning season, although with a loss of mass in both dietary groups. Relative fecundity through the season was significantly lower in stressed G. morhua fed LF compared to unstressed G. morhua fed the same diet. Stressed G. morhua had a higher variability in weekly amount of eggs spawned, spawning occurred more irregularly, and the spawning period lasted longer than in unstressed G. morhua. Several egg quality variables were also affected: eggs from G. morhua fed LF and exposed to stress had lower fertilization and hatching rates compared to the unstressed G. morhua fed the same diet as well as all G. morhua fed HF. Gadus morhua fed a low-fat diet appeared less tolerant to stress than fish fed a high-fat diet.

High temperature Seebeck coefficient and resistance measurement system for thermoelectric materials in the thin disk geometry.

A versatile apparatus to measure the cross-plane Seebeck coefficient and the resistivity of bulk samples shaped as disks or thin plates, over a temperature range of 300 K-620 K with possible extension to higher temperatures, is presented. It is constructed from readily available equipment and instrumentation with parts that are easily manufactured. The Seebeck coefficient is measured over an average region of the sample under steady-state conditions. The sample resistance is measured using a four-point alternating current method and scaled to room temperature measurements with known geometry to calculate resistivity. A variety of sample shapes are supported. Most importantly, the support of the thin disk geometry allows for the very same samples to be used in a laser flash instrument. The design allows for rough vacuum, high vacuum, or purging with inert gases in the sample chamber. Measurements on thermoelectric ZnSb and a Ni reference material are presented.

Identification of a bacterial di-haem cytochrome c peroxidase from Methylomicrobium album BG8.

The nucleotide sequence of an open reading frame (corB) downstream of the copper-repressible CorA-encoding gene of the methanotrophic bacterium Methylomicrobium album BG8 was obtained by restriction enzyme digestion and inverse PCR. The amino acid sequence deduced from this gene showed significant sequence similarity to the surface-associated di-haem cytochrome c peroxidase (SACCP) previously isolated from Methylococcus capsulatus (Bath), including both c-type haem-binding motifs. Homology analysis placed this protein, phylogenetically, within the subfamily containing the M. capsulatus SACCP of the bacterial di-haem cytochrome c peroxidase (BCCP) family of proteins. Immunospecific recognition confirmed synthesis of the M. album CorB as a protein non-covalently associated with the outer membrane and exposed to the periplasm. corB expression is regulated by the availability of copper ions during growth and the protein is most abundant in M. album when grown at a low copper-to-biomass ratio, indicating an important physiological role of CorB under these growth conditions. corB was co-transcribed with the gene encoding CorA, constituting a copper-responding operon, which appears to be under the control of a sigma(54)-dependent promoter. M. album CorB is the second isolated member of the recently described subfamily of the BCCP family of proteins. So far, these proteins have only been described in methanotrophic bacteria.

The presence of multiple c-type cytochromes at the surface of the methanotrophic bacterium Methylococcus capsulatus (Bath) is regulated by copper.

Identification of surface proteins is essential to understand bacterial communication with its environment. Analysis of the surface-associated proteins of Methylococcus capsulatus (Bath) revealed a highly dynamic structure responding closely to the availability of copper in the medium in the range from approximately 0 to 10 microM. Several c-type cytochromes, including three novel multihaem proteins, are present at the cellular surface, a feature that is otherwise a peculiarity of dissimilatory metal-reducing bacteria. At low copper concentrations, the cytochrome c(553o) and the cytochrome c(553o) family protein, encoded by the MCA0421 and MCA0423 genes, respectively, are major constituents of the surfaceome and show a fine-tuned copper-dependent regulation of expression. Two novel members of the cytochrome c(553o) family were identified: MCA0338 was abundant between 5 and 10 microM copper, while MCA2259 was detected only in the surface fraction obtained from approximately 0 microM copper cultures. The presence at the bacterial surface of several c-type cytochromes, generally involved in energy transduction, indicates strongly that redox processes take place at the bacterial surface. Due to the unique role of copper in the biology of M. capsulatus (Bath), it appears that c-type cytochromes have essential functions in copper homeostasis allowing the cells to adapt to varying copper exposure.

A quantitative study of valence electron transfer in the skutterudite compound CoP(3) by combining x-ray induced Auger and photoelectron spectroscopy.

We use the sum of the ionization and Auger energy, the so-called Auger parameter, measured from the x-ray photoelectron spectrum, to study the valence electron distribution in the skutterudite CoP(3). The electron transfer between Co and P was estimated using models relating changes in Auger parameter values to charge transfer. It was found that each P atom gains 0.24 e(-), and considering the unit formula CoP(3) this is equivalent to a donation of 0.72 e(-) per Co atom. This is in agreement with a recent electron energy-loss spectroscopy study, which indicates a charge transfer of 0.77 e(-)/atom from Co to P.

Parameter estimation from Rician-distributed data sets using a maximum likelihood estimator: application to T1 and perfusion measurements.

General expressions are presented to calculate the maximum likelihood (ML) estimator and corresponding Fisher matrix for Rician-distributed data sets. This estimator results in the most precise, unbiased estimations of T1 from magnitude data sets, even when low signal-to-noise ratios (<6) are present. By optimizing the sample point distributions for inversion-recovery experiments, a 32% increase in precision of the estimated T1 is obtained, compared with a linear sampling scheme. Perfusion rates are estimated from combined data sets of the slice- and nonslice-selective inversion-recovery experiments, as obtained with the flow-sensitive alternating inversion recovery (FAIR) technique. The ML estimator for the combined data set results in the most precise, unbiased estimations of the perfusion rate. Error analysis shows that very high signal-to-noise ratios are required for precise estimation of perfusion rates from FAIR experiments.

Absolute metabolite quantification by in vivo NMR spectroscopy: IV. Multicentre trial on MRSI localisation tests.

The difference between the experimental and theoretical spatial response function (SRF) of a narrow tube with water is used for a localization test for magnetic resonance spectroscopic imaging (MRSI). From this difference a quantitative performance parameter is derived for the relative amount of signal within a limited region in the field of view. The total signal loss by the MRSI experiment and eddy currents is described by a parameter SL derived from the signal intensities of two echoes. Results of a European multi-centre trial show that this approach is suited for assessment of MRSI localization performance.

In vitro evaluation of a novel bioreactor based on an integral oxygenator and a spirally wound nonwoven polyester matrix for hepatocyte culture as small aggregates.

BACKGROUND/AIMS: The development of custom-made bioreactors for use as a bioartificial liver (BAL) is considered to be one of the last challenges on the road to successful temporary extracorporeal liver support therapy. We devised a novel bioreactor (patent pending) which allows individual perfusion of high density cultured hepatocytes with low diffusional gradients, thereby more closely resembling the conditions in the intact liver lobuli. METHODS: The bioreactor consists of a spirally wound nonwoven polyester matrix, i.e. a sheet-shaped, three-dimensional framework for hepatocyte immobilization and aggregation, and of integrated hydrophobic hollow-fiber membranes for decentralized oxygen supply and CO2 removal. Medium (plasma in vivo) was perfused through the extrafiber space and therefore in direct hepatocyte contact. Various parameters were assessed over a period of 4 days including galactose elimination, urea synthesis, lidocaine elimination, lactate/pyruvate ratios, amino acid metabolism, pH, the last day being reserved exclusively for determination of protein secretion. RESULTS: Microscopic examination of the hepatocytes revealed cytoarchitectural characteristics as found in vivo. The biochemical performance of the bioreactor remained stable over the investigated period. The urea synthesizing capacity of hepatocytes in the bioreactor was twice that of hepatocytes in monolayer cultures. Flow sensitive magnetic resonance imaging (MRI) revealed that the bioreactor construction ensured medium flow through all parts of the device irrespective of its size. CONCLUSIONS: The novel bioreactor showed encouraging efficiency. The device is easy to manufacture with scale-up to the liver mass required for possible short-term support of patients in hepatic failure.

L-ornithine vs. L-ornithine-L-aspartate as a treatment for hyperammonemia-induced encephalopathy in rats.

BACKGROUND/AIMS: The effect of L-ornithine (ORN) and L-ornithine-L-aspartate (OA) therapy on "extracerebral" nitrogen metabolism, brain metabolism and neurotransmission has been investigated in portacaval shunted rats with hyperammonemia-induced encephalopathy. METHODS: One day before ammonium-acetate infusion, a portacaval shunt was performed in three experimental groups: 1-control rats, 2-ORN-treated rats and 3-OA-treated rats. Ammonium-acetate was given as an intravenous bolus injection (0.4 mmol.kg bw-1) followed by a constant infusion (1.9 mmol.kg bw-1.h-1) so that steady-state blood ammonia concentrations (500-800 microM) were obtained in the course of 5 h. After 1 h, ammonium-acetate infusion, either L-ornithine or L-ornithine-L-aspartate, was infused for the next 4 h (3.0 mmol.kg bw-1.h-1) in the treated groups. The following parameters were measured: clinical grade of encephalopathy, EEG activity (n = 10 - 20/group), amino acids in plasma (n = 10 - 20/group) and brain dialysate (n = 5 - 9/group), and brain metabolites obtained by in vivo cerebral 1H-MRS (n = 4 - 6/group). RESULTS: ORN and OA treatment resulted in significantly lower blood (34% and 39%) and brain (42% and 22%) ammonia concentrations, significantly higher urea production (39% and 86%) and significantly smaller increases in brain glutamine and lactate concentrations than in controls. These changes were associated with a significantly smaller increase in clinical grade of encephalopathy in ORN- and OA-treated rats, and a significant improvement in EEG activity in ORN-treated rats. OA-treated rats showed a significant increase in aspartate and glutamate concentrations in brain dialysate. CONCLUSIONS: The beneficial effects of both treatments on the manifestations of hyperammonemia-induced encephalopathy can be explained by a reduction in blood and brain ammonia concentrations. It is suggested that when OA is administered, the effect of ornithine is partly counteracted by aspartate, inducing high brain extracellular concentrations of the two excitatory amino acids glutamate and aspartate, and perhaps causing overstimulation of NMDA receptors.

Spatial resolution and spectral information content of proton NMR spectroscopic imaging of tumour metabolism.

The value of metabolic proton NMR spectroscopic imaging to detect and classify tumours increases with the spatial resolution and the information content of the spectra. Several factors influencing these quantities are discussed.