Multilocus sequence analysis reveals different lineages of Pseudomonas anguilliseptica associated with disease in farmed lumpfish (Cyclopterus lumpus L.)

The bacterium Pseudomonas anguilliseptica has in recent years emerged as a serious threat to production of lumpfish in Norway. Little is known about the population structure of this bacterium despite its association with disease in a wide range of different fish species throughout the world. The phylogenetic relationships between 53 isolates, primarily derived from diseased lumpfish, but including a number of reference strains from diverse geographical origins and fish species, were reconstructed by Multi-Locus Sequence Analysis (MLSA) using nine housekeeping genes (rpoB, atpD, gyrB, rpoD, ileS, aroE, carA, glnS and recA). MLSA revealed a high degree of relatedness between the studied isolates, altough the seven genotypes identified formed three main phylogenetic lineages. While four genotypes were identified amongst Norwegian lumpfish isolates, a single genotype dominated, irrespective of geographic origin. This suggests the existence of a dominant genotype associated with disease in production of lumpfish in Norwegian aquaculture. Elucidation of the population structure of the bacterium has provided valuable information for potential future vaccine development.publishedVersio

Seasonal progression of microbial communities on the Faroe shelf

<div><p></p><p>Microorganisms, such as phytoplankton and bacterioplankton, are affected by turnover rates of nutrients and show great fluctuations over seasons. In productive coastal areas, the biomass of bacterioplankton can be in the same range as that of phytoplankton. In these coastal areas the initiation and intensity of the spring bloom is highly variable between years. This variability is reflected in higher trophic levels and is therefore of major importance for ecosystems such as that of the Faroe Islands. However, one of the major unknown components is the bacterioplankton. We report a study on seasonal dynamics from March–September of nutrients, phytoplankton composition and their co-fluctuation with bacterial succession. For this purpose SAR11, <i>Bacteroidetes</i>, <i>Roseobacter</i> and cyanobacteria were relatively quantified using real-time PCR based on 16S DNA and total bacteria was assessed by epifluorescence microscopy. The phytoplankton species were identified using the inverted microscope technique. These data showed a pronounced diatom spring bloom and autumn bloom reflected by a corresponding decrease in nitrate and silicate (<i>R</i>² = 0.72 and 0.77, respectively). The cessation of the phytoplankton bloom did not, however, seem to be explained by nutrient limitation. <i>Roseobacter</i> bloomed during the phytoplankton spring bloom, while the other bacterial groups increased during low phytoplankton biomass. This suggests that algal substrate availability and environmental conditions provide the opportunity for bacterial communities to develop a post-spring bloom. This study reveals how planktonic bacteria adapt with their surroundings, enhancing the microbial loop post-spring bloom and providing a potentially important food resource for higher trophic levels.</p></div

Culture Negative Listeria monocytogenes Meningitis Resulting in Hydrocephalus and Severe Neurological Sequelae in a Previously Healthy Immunocompetent Man with Penicillin Allergy

A previously healthy 74-year-old Caucasian man with penicillin allergy was admitted with evolving headache, confusion, fever, and neck stiffness. Treatment for bacterial meningitis with dexamethasone and monotherapy ceftriaxone was started. The cerebrospinal fluid showed negative microscopy for bacteria, no bacterial growth, and negative polymerase chain reaction for bacterial DNA. The patient developed hydrocephalus on a second CT scan of the brain on the 5th day of admission. An external ventricular catheter was inserted and Listeria monocytogenes grew in the cerebrospinal fluid from the catheter. The patient had severe neurological sequelae. This case report emphasises the importance of covering empirically for Listeria monocytogenes in all patients with penicillin allergy with suspected bacterial meningitis. The case also shows that it is possible to have significant infection and inflammation even with negative microscopy, negative cultures, and negative broad range polymerase chain reaction in cases of Listeria meningitis. Follow-up spinal taps can be necessary to detect the presence of Listeria monocytogenes

Localised Infection of Atlantic Salmon Epithelial Cells by HPR0 Infectious Salmon Anaemia Virus.

Infectious salmon anaemia (ISA) is an important, systemic viral disease of farmed Atlantic salmon, Salmo salar L. Endothelial cells are the main target cells for highly virulent HPR-deleted ISA virus (ISAV) types. Here we examine the pathogenesis of non-virulent ISAV HPR0 infections, presenting evidence of an epithelial tropism for this virus type, including actual infection and replication in the epithelial cells. Whereas all HPR0 RT-qPCR positive gills prepared for cryosection tested positive by immunohistochemistry (IHC) and immunofluorescent labelling, only 21% of HPR0 RT-qPCR positive formalin-fixed paraffin-embedded gills were IHC positive, suggesting different methodological sensitivities. Only specific epithelial cell staining was observed and no staining was observed in endothelial cells of positive gills. Furthermore, using an ISAV segment 7 RT-PCR assay, we demonstrated splicing of HPR0, suggesting initial activation of the replication machinery in the epithelial gill cells. Immunological responses were investigated by the expression of interferon-related genes (e.g. Mx and γIP) and by ELISA for presence of anti-ISAV antibodies on samples taken sequentially over several months during an episode of transient HPR0 infection. All fish revealed a variable, but increased expression of the immunological markers in comparison to normal healthy fish. Taken together, we conclude that HPR0 causes a localized epithelial infection of Atlantic salmon

MOESM1 of Infectious salmon anaemia virus (ISAV) mucosal infection in Atlantic salmon

Additional file 1. Statistical modelling of 4 immune marker expression profiles. Statistical modelling of 4 immune marker expression profiles, type I IFN (A), Mx (B), type II IFN (C) and ÎłIP (D) in hind gut of fish infected with high virulent (dashed line and triangles) or low virulent (solid line and circles) strains measured by real-time RT-qPCR. Dotted lines indicate 95% confidence intervals

Low virulent infectious salmon anaemia virus (ISAV) replicates and initiates the immune response earlier than a highly virulent virus in Atlantic salmon gills

International audienceObservations from the field and experimental evidence suggest that different strains of infectious salmon anaemia virus (ISAV) can induce disease of varying severity in Atlantic salmon. Variation in host mortality and dissemination of ISAV isolates with high and low virulence was investigated using immersion challenge; from which mortality, pathological, immunohistochemical and preliminary molecular results have been previously published. Here, real-time RT-PCR analysis and statistical modelling have been used to further investigate variation in virus load and the response of four select immune genes. Expression of type I and II interferon (IFN), Mx and γIFN induced protein (γIP) to high and low pathogenic virus infection were examined in gill, heart and anterior kidney. In addition, a novel RNA species-specific assay targeting individual RNA types was used to investigate the separate viral processes of transcription and replication. Unexpectedly, the low virulent ISAV (LVI) replicated and transcribed more rapidly in the gills compared to the highly virulent virus (HVI). Subsequently LVI was able to disseminate to the internal organs more quickly and induced a more rapid systemic immune response in the host that may have offered some protection. Contrary to this, HVI initially progressed more slowly in the gills resulting in a slower generalised infection. However HVI ultimately reached a higher viral load and induced a greater mortality

RT-qPCR of gills and gill swabs, and immunostaining on frozen gills from farm IV.

<p>RT-qPCR of gills and gill swabs, and immunostaining on frozen gills from farm IV.</p

Evolution of the <i>Piscine orthoreovirus</i> Genome Linked to Emergence of Heart and Skeletal Muscle Inflammation in Farmed Atlantic Salmon (<i>Salmo salar</i>)

Heart and skeletal muscle inflammation (HSMI) in farmed Atlantic salmon (Salmo salar) was first diagnosed in Norway in 1999. The disease is caused by Piscine orthoreovirus-1 (PRV-1). The virus is prevalent in farmed Atlantic salmon, but not always associated with disease. Phylogeny and sequence analyses of 31 PRV-1 genomes collected over a 30-year period from fish with or without HSMI, grouped the viral sequences into two main monophylogenetic clusters, one associated with HSMI and the other with low virulent PRV-1 isolates. A PRV-1 strain from Norway sampled in 1988, a decade before the emergence of HSMI, grouped with the low virulent HSMI cluster. The two distinct monophylogenetic clusters were particularly evident for segments S1 and M2. Only a limited number of amino acids were unique to the association with HSMI, and they all located to S1 and M2 encoded proteins. The observed co-evolution of the S1-M2 pair coincided in time with the emergence of HSMI in Norway, and may have evolved through accumulation of mutations and/or segment reassortment. Sequences of S1-M2 suggest selection of the HSMI associated pair, and that this segment pair has remained almost unchanged in Norwegian salmon aquaculture since 1997. PRV-1 strains from the North American Pacific Coast and Faroe Islands have not undergone this evolution, and are more closely related to the PRV-1 precursor strains not associated with clinical HSMI