Publications by authors named "D Saulnier"

92 Publications

Dual RNAseq highlights the kinetics of skin microbiome and fish host responsiveness to bacterial infection.

Anim Microbiome 2021 May 7;3(1):35. Epub 2021 May 7.

Ifremer, IRD, Institut Louis-Malardé, Univ Polynésie Française, EIO, F-98719 Taravao, Tahiti, Polynésie Française.

Background: Tenacibaculum maritimum is a fish pathogen known for causing serious damage to a broad range of wild and farmed marine fish populations worldwide. The recently sequenced genome of T. maritimum strain NCIMB 2154 provided unprecedented information on the possible molecular mechanisms involved in the virulence of this species. However, little is known about the dynamic of infection in vivo, and information is lacking on both the intrinsic host response (gene expression) and its associated microbiota. Here, we applied complementary omic approaches, including dual RNAseq and 16S rRNA gene metabarcoding sequencing using Nanopore and short-read Illumina technologies to unravel the host-pathogen interplay in an experimental infection system using the tropical fish Platax orbicularis as model.

Results: We showed that the infection of the host is characterised by an enhancement of functions associated with antibiotic and glucans catabolism functions but a reduction of sulfate assimilation process in T. maritimum. The fish host concurrently displays a large panel of immune effectors, notably involving innate response and triggering acute inflammatory response. In addition, our results suggest that fish activate an adaptive immune response visible through the stimulation of T-helper cells, Th17, with congruent reduction of Th2 and T-regulatory cells. Fish were, however, largely sensitive to infection, and less than 25% survived after 96 hpi. These surviving fish showed no evidence of stress (cortisol levels) or significant difference in microbiome diversity compared with controls at the same sampling time. The presence of T. maritimum in resistant fish skin and the total absence of any skin lesions suggest that these fish did not escape contact with the pathogen, but rather that some mechanisms prevented pathogens entry. In resistant individuals, we detected up-regulation of specific immune-related genes differentiating resistant individuals from controls at 96 hpi, which suggests a possible genomic basis of resistance, although no genetic variation in coding regions was found.

Conclusion: Here we focus in detail on the interplay between common fish pathogens and host immune response during experimental infection. We further highlight key actors of defence response, pathogenicity and possible genomic bases of fish resistance to T. maritimum.
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http://dx.doi.org/10.1186/s42523-021-00097-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8106148PMC
May 2021

Description of the unusual digestive tract of and the potential impact of infection.

PeerJ 2020 24;8:e9966. Epub 2020 Sep 24.

MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, Montpellier, France.

Background: Ephippidae fish are characterized by a discoid shape with a very small visceral cavity. Among them has a high economic potential due to its flesh quality and flesh to carcass ratio. Nonetheless, the development of its aquaculture is limited by high mortality rates, especially due to infection, occurring one to three weeks after the transfer of fishes from bio-secure land-based aquaculture system to the lagoon cages for growth. Among the lines of defense against this microbial infection, the gastrointestinal tract (GIT) is less studied. The knowledge about the morphofunctional anatomy of this organ in is still scarce. Therefore, the aims of this study are to characterize the GIT in non-infected juveniles to then investigate the impact of on this multifunctional organ.

Methods: In the first place, the morpho-anatomy of the GIT in non-infected individuals was characterized using various histological techniques. Then, infected individuals, experimentally challenged by were analysed and compared to the previously established GIT reference.

Results: The overlapped shape of the GIT of is probably due to its constrained compaction in a narrow visceral cavity. Firstly, the GIT was divided into 10 sections, from the esophagus to the rectum. For each section, the structure of the walls was characterized, with a focus on mucus secretions and the presence of the Na/K ATPase pump. An identification key allowing the characterization of the GIT sections using histology is given. Secondly, individuals challenged with exhibited differences in mucus type and proportion and, modifications in the mucosal and muscle layers. These changes could induce an imbalance in the trade-off between the GIT functions which may be in favour of protection and immunity to the disadvantage of nutrition capacities.
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http://dx.doi.org/10.7717/peerj.9966DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7520087PMC
September 2020

The transfer of clinical prediction models for early trauma care had uncertain effects on mistriage.

J Clin Epidemiol 2020 12 22;128:66-73. Epub 2020 Aug 22.

Department of Global Public Health, Karolinska Institutet, Stockholm, Sweden.

Objectives: This study aimed to assess how transfers of clinical prediction models for early trauma care between different care contexts within a single health system affected mistriage rates.

Study Design And Setting: Patients aged 15 years or older, registered between 2011 and 2016 in the Swedish national trauma registry, SweTrau, were included. Three data set groups were created: high- and low-volume centers, metropolitan and nonmetropolitan centers, and multicenters and single centers. Clinical prediction models were developed using logistic regression in each data set group and transferred between data sets within groups. Model performance was evaluated using mistriage rate, undertriage rate, and overtriage rate. Multiple imputation using chained equations was used to handle missing data. Model performance was reported as medians with 95% confidence intervals (CIs).

Results: A total of 26,965 patients were included. Changes in mistriage rates after transfer ranged from -0.25 (95% CI -0.21 to 0.04) to 0.29 (95% CI 0.13-0.39). Both overtriage and undertriage rates were affected.

Conclusions: Transferring clinical prediction models for early trauma care is associated with substantial uncertainty in regards to the effect on model performance. Depending on the care context, model transfer led to either increased or decreased mistriage. Overtriage was more affected by model transfer than undertriage.
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http://dx.doi.org/10.1016/j.jclinepi.2020.08.014DOI Listing
December 2020

Quorum Sensing Inhibitory and Antifouling Activities of New Bromotyrosine Metabolites from the Polynesian Sponge n. sp.

Mar Drugs 2020 May 21;18(5). Epub 2020 May 21.

IRD, Université de la Polynésie française, Ifremer, ILM, EIO, Papeete F-98713, French Polynesia.

Four new brominated tyrosine metabolites, aplyzanzines C-F (-), were isolated from the French Polynesian sponge n. sp., along with the two known 2-aminoimidazolic derivatives, purealidin A () and previously isolated, respectively, from the sponges and Verongula sp. Their structures were assigned based on the interpretation of their NMR and HRMS data. The compounds exhibited quorum sensing inhibition (QSi) and antifouling activities against several strains of bacteria and microalgae. To our knowledge, the QSi activity of this type of bromotyrosine metabolite is described here for the first time.
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http://dx.doi.org/10.3390/md18050272DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7281015PMC
May 2020

Genetic diversity and population structure of Tenacibaculum maritimum, a serious bacterial pathogen of marine fish: from genome comparisons to high throughput MALDI-TOF typing.

Vet Res 2020 May 7;51(1):60. Epub 2020 May 7.

Université Paris-Saclay, INRAE, UVSQ, VIM, 78350, Jouy-En-Josas, France.

Tenacibaculum maritimum is responsible for tenacibaculosis, a devastating marine fish disease. This filamentous bacterium displays a very broad host range and a worldwide geographical distribution. We analyzed and compared the genomes of 25 T. maritimum strains, including 22 newly draft-sequenced genomes from isolates selected based on available MLST data, geographical origin and host fish. The genome size (~3.356 Mb in average) of all strains is very similar. The core genome is composed of 2116 protein-coding genes accounting for ~75% of the genes in each genome. These conserved regions harbor a moderate level of nucleotide diversity (~0.0071 bp) whose analysis reveals an important contribution of recombination (r/m ≥ 7) in the evolutionary process of this cohesive species that appears subdivided into several subgroups. Association trends between these subgroups and specific geographical origin or ecological niche remains to be clarified. We also evaluated the potential of MALDI-TOF-MS to assess the variability between T. maritimum isolates. Using genome sequence data, several detected mass peaks were assigned to ribosomal proteins. Additionally, variations corresponding to single or multiple amino acid changes in several ribosomal proteins explaining the detected mass shifts were identified. By combining nine polymorphic biomarker ions, we identified combinations referred to as MALDI-Types (MTs). By investigating 131 bacterial isolates retrieved from a variety of isolation sources, we identified twenty MALDI-Types as well as four MALDI-Groups (MGs). We propose this MALDI-TOF-MS Multi Peak Shift Typing scheme as a cheap, fast and an accurate method for screening T. maritimum isolates for large-scale epidemiological surveys.
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http://dx.doi.org/10.1186/s13567-020-00782-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7204230PMC
May 2020
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