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Sergio H. Marshall - One of the best experts on this subject based on the ideXlab platform.

  • Defining the role of Caligus rogercresseyi in transmission and spreading of Piscirickettsia salmonis
    Aquaculture, 2020
    Co-Authors: Alvaro Labra, Sandra Bravo, Sergio H. Marshall
    Abstract:

    Abstract The epidemiological role of the association of Piscirickettsia salmonis and Caligus rogercresseyi in infected salmonid fishes has not been clearly elucidated, which has led to speculation and insecurity regarding the design of efficient therapeutic strategies for dual infections. We therefore decided to assess if there is a functional association between transmission and/or spreading of the bacteria in dually infected fish under in vivo and in vitro conditions. This was done by kinetically analysing expression of the bacteria in the parasite from naturally as well as in induced infections. We observed that under any of the conditions assayed, biological expression of the bacteria could not be detected neither in any developmental stages of the parasite, nor in target organs of the dually infected fish. Thus, we suggest that Caligus rogercresseyi does not act as a biological vector for P. salmonis, neither as a mechanical vector, as in this study, P. salmonis was not able to remain on the lice for 1 h after becoming detached from the infected host. Notwithstanding, a transient association between the two agents was detected early in their encounters with the fish, a situation that might explain the ambiguities about their functional interactive roles in the literature.

  • Selection and validation of reliable housekeeping genes to evaluate Piscirickettsia salmonis gene expression.
    Infection genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases, 2018
    Co-Authors: P. Flores-herrera, Sergio H. Marshall, Oscar Arredondo-zelada, Fernando A. Gómez
    Abstract:

    Piscirickettsia salmonis is a highly aggressive facultative intracellular bacterium that challenges the sustainability of Chilean salmon production. Due to the limited knowledge of its biology, there is a need to identify key molecular markers that could help define the pathogenic potential of this bacterium. We think a model system should be implemented that efficiently evaluates the expression of putative bacterial markers by using validated, stable, and highly specific housekeeping genes to properly select target genes, which could lead to identifying those responsible for infection and disease induction in naturally infected fish. Here, we selected a set of validated reference or housekeeping genes for RT-qPCR expression analyses of P. salmonis under different growth and stress conditions, including an in vitro infection kinetic. After a thorough screening, we selected sdhA as the most reliable housekeeping gene able to represent stable and highly specific host reference genes for RT-qPCR-driven P. salmonis analysis.

  • Draft genomes and reference transcriptomes extend the coding potential of the fish pathogen Piscirickettsia salmonis
    Elsevier, 2018
    Co-Authors: Angela D. Millar, Sergio H. Marshall, Paz Tapia, Fernando A. Gómez, Derie E. Fuentes, Jorge H. Valdes
    Abstract:

    Background: Draft and complete genome sequences from bacteria are key tools to understand genetic determinants involved in pathogenesis in several disease models. Piscirickettsia salmonis is a Gram-negative bacterium responsible for the Salmon Rickettsial Syndrome (SRS), a bacterial disease that threatens the sustainability of the Chilean salmon industry. In previous reports, complete and draft genome sequences have been generated and annotated. However, the lack of transcriptome data underestimates the genetic potential, does not provide information about transcriptional units and contributes to disseminate annotation errors. Results: Here we present the draft genome and transcriptome sequences of four P. salmonis strains. We have identified the transcriptional architecture of previously characterized virulence factors and trait-specific genes associated to cation uptake, metal efflux, antibiotic resistance, secretion systems and other virulence factors. Conclusions: This data has provided a refined genome annotation and also new insights on the transcriptional structures and coding potential of this fish pathogen.How to cite: Millar AD, Tapia P, Gomez FA, et al. Draft genomes and reference transcriptomes extend the coding potential of the fish pathogen Piscirickettsia salmonis. Electron J Biotechnol 2018;33. https://doi.org/10.1016/j.ejbt.2018.04.002. Keywords: Bacterial genomes, Coding potential, Comparative analysis, Draft genome, Piscirickettsia salmonis, Reference transcriptome, Refined annotation, Salmon Rickettsial Syndrome, Salmonid

  • Draft genomes and reference transcriptomes extend the coding potential of the fish pathogen Piscirickettsia salmonis
    Electronic Journal of Biotechnology, 2018
    Co-Authors: Angela D. Millar, Sergio H. Marshall, Paz Tapia, Fernando A. Gómez, Derie E. Fuentes, Jorge Valdés
    Abstract:

    Background: Draft and complete genome sequences from bacteria are key tools to understand genetic determinants involved in pathogenesis in several disease models. Piscirickettsia salmonis is a Gram-negative bacterium responsible for the Salmon Rickettsial Syndrome (SRS), a bacterial disease that threatens the sustainability of the Chilean salmon industry. In previous reports, complete and draft genome sequences have been generated and annotated. However, the lack of transcriptome data underestimates the genetic potential, does not provide information about transcriptional units and contributes to disseminate annotation errors. Results: Here we present the draft genome and transcriptome sequences of four P. salmonis strains. We have identified the transcriptional architecture of previously characterized virulence factors and trait-specific genes associated to cation uptake, metal efflux, antibiotic resistance, secretion systems and other virulence factors. Conclusions: This data has provided a refined genome annotation and also new insights on the transcriptional structures and coding potential of this fish pathogen.

  • Genome-scale metabolic reconstruction for the insidious bacterium in aquaculture Piscirickettsia salmonis
    Bioresource technology, 2016
    Co-Authors: Pablo Fuentealba, Sergio H. Marshall, Camila Aros, Yesenia Latorre, Irene Martínez, Pau Ferrer, Joan Albiol, Claudia Altamirano
    Abstract:

    Abstract Piscirickettsia salmonis is a fish bacterium that causes the disease piscirickettsiosis in salmonids. This pathology is partially controlled by vaccines. The lack of knowledge has hindered its culture on laboratory and industrial scale. The study describes the metabolic phenotype of P. salmonis in culture. This study presents the first genome-scale model ( i PF215) of the LF-89 strain of P. salmonis , describing the central metabolic pathway, biosynthesis and molecule degradation and transport mechanisms. The model was adjusted with experiment data, allowing the identification of the capacities that were not predicted by the automatic annotation of the genome sequences. The i PF215 model is comprised of 417 metabolites, 445 reactions and 215 genes, was used to reproduce the growth of P. salmonis (μ max 0.052 ± 0.005 h −1 ). The metabolic reconstruction of the P. salmonis LF-89 strain obtained in this research provides a baseline that describes the metabolic capacities of the bacterium and is the basis for developing improvements to its cultivation for vaccine formulation.

Pablo Conejeros - One of the best experts on this subject based on the ideXlab platform.

  • Host genetic variation explains reduced protection of commercial vaccines against Piscirickettsia salmonis in Atlantic salmon.
    Scientific reports, 2020
    Co-Authors: Carolina Figueroa, Pablo Conejeros, Pamela Veloso, Lenin Espin, Brian Dixon, Débora Torrealba, Islam Said Elalfy, Juan Manuel Afonso, Carlos Soto, José A. Gallardo
    Abstract:

    Vaccination is a widely used control strategy to prevent Piscirickettsia salmonis causing disease in salmon farming. However, it is not known why all the currently available commercial vaccines generally fail to protect against this pathogenic bacteria. Here, we report, from two different populations, that between-family variation is a strong intrinsic factor that determines vaccine protection for this disease. While in some full-sib families, the protection added by vaccination increased the survival time in 13 days in comparison with their unvaccinated siblings; in other families, there was no added protection by vaccination or even it was slightly negative. Resistance to P. salmonis, measured as days to death, was higher in vaccinated than unvaccinated fish, but only a moderate positive genetic correlation was obtained between these traits. This disputes a previous hypothesis, that stated that both traits were fully controlled by the same genes, and challenges the use of unvaccinated fish as gold standard for evaluating and selecting fish resistant to P. salmonis, particularly if the offspring will be vaccinated. More studies are necessary to evaluate if variation in the host immune response to vaccination could explain the between-family differences in resistance observed in vaccinated fish.

  • Electrochemical detection of Piscirickettsia salmonis genomic DNA from salmon samples using solid-phase recombinase polymerase amplification
    Analytical and Bioanalytical Chemistry, 2016
    Co-Authors: Jonathan Sabaté Río, Pablo Conejeros, Marketa Svobodova, Paulina Bustos, Ciara K. O’sullivan
    Abstract:

    Electrochemical detection of solid-phase isothermal recombinase polymerase amplification (RPA) of Piscirickettsia salmonis in salmon genomic DNA is reported. The electrochemical biosensor was constructed by surface functionalization of gold electrodes with a thiolated forward primer specific to the genomic region of interest. Solid-phase RPA and primer elongation were achieved in the presence of the specific target sequence and biotinylated reverse primers. The formation of the subsequent surface-tethered duplex amplicons was electrochemically monitored via addition of streptavidin-linked HRP upon completion of solid-phase RPA. Successful quantitative amplification and detection were achieved in less than 1 h at 37 °C, calibrating with PCR-amplified genomic DNA standards and achieving a limit of detection of 5 · 10^−8 μg ml^−1 (3 · 10^3 copies in 10 μl). The presented system was applied to the analysis of eight real salmon samples, and the method was also compared to qPCR analysis, observing an excellent degree of correlation. Graphical abstract Schematic of use of electrochemical RPA for detection of Psiricketessia salmonis in salmon liver

  • Electrochemical detection of Piscirickettsia salmonis genomic DNA from salmon samples using solid-phase recombinase polymerase amplification.
    Analytical and bioanalytical chemistry, 2016
    Co-Authors: Jonathan Sabaté Del Río, Pablo Conejeros, Marketa Svobodova, Paulina Bustos, Ciara K. O'sullivan
    Abstract:

    Electrochemical detection of solid-phase isothermal recombinase polymerase amplification (RPA) of Piscirickettsia salmonis in salmon genomic DNA is reported. The electrochemical biosensor was constructed by surface functionalization of gold electrodes with a thiolated forward primer specific to the genomic region of interest. Solid-phase RPA and primer elongation were achieved in the presence of the specific target sequence and biotinylated reverse primers. The formation of the subsequent surface-tethered duplex amplicons was electrochemically monitored via addition of streptavidin-linked HRP upon completion of solid-phase RPA. Successful quantitative amplification and detection were achieved in less than 1 h at 37 °C, calibrating with PCR-amplified genomic DNA standards and achieving a limit of detection of 5 · 10−8 μg ml−1 (3 · 103 copies in 10 μl). The presented system was applied to the analysis of eight real salmon samples, and the method was also compared to qPCR analysis, observing an excellent degree of correlation.

  • MHC mediated resistance to Piscirickettsia salmonis in salmonids farmed in Chile
    Aquaculture, 2011
    Co-Authors: Daniela Gómez, Pablo Conejeros, Sofia Consuegra, Sergio H. Marshall
    Abstract:

    Abstract Piscirickettsia salmonis is the most persistent and threatening pathogen for Chilean aquaculture. In our search for alternatives to control the disease, we analyzed class II polymorphic genes of the Major Histocompatibility Complex (MHC) in juvenile fish trying to find alleles that may confer resistance or susceptibility to the agent in the three major salmonid species cultured in Chile: Salmo salar, Oncorhynchus mykiss and Oncorhynchus kisutch . DNA from farmed fish naturally exposed to the pathogen in different aquaculture centers in Chile were analyzed via PCR for the MHC class II alpha and beta loci ( DAA and DAB ), and characterized by denaturant gradient gel electrophoresis (DGGE) followed by DNA sequencing. The comparison between alleles present in either healthy or diseased individuals clearly demonstrated allelic differences between the two populations, specifically for the DAB locus in the three species and only for the DAA locus in S. salar. We conclude that a thorough analysis of the allelic differences identified between fish naturally susceptible/resistant to P. salmonis could potentiate MHC to become a powerful genetic marker for both prophylactic and breeding purposes.

  • immunological characterization of a bacterial protein isolated from salmonid fish naturally infected with Piscirickettsia salmonis
    Vaccine, 2007
    Co-Authors: Sergio H. Marshall, Pablo Conejeros, Marcela Zahr, Jorge Olivares, Fernando Jimenez Gomez, Patricio Cataldo, Vitalia Henriquez
    Abstract:

    The Salmon Rickettsia syndrome (SRS) remains a major infectious disease in the Chilean aquaculture. A limited number of Piscirickettsia salmonis proteins have been characterized so far for their use as potential candidates for vaccines studies. In this study, we identified and expressed a highly immunogenic protein of P. salmonis extracted by selective hydrophobicity from crude-cell macerates of naturally infected salmonid fish. One and two-D PAGE gels followed by Western blot analysis with a battery of polyclonal anti-P. salmonis antibodies have allowed the isolation of the target protein. Basic local alignment search (BLAST) done after partial sequencing of the pure protein identified it as a member of the heat-shock protein (HSP) family of prokaryotes. The protein, named ChaPs, was cloned as a single open reading frame encoding 545 amino acid residues with a predicted molecular mass of 57.3 kDa. The amplicon representing the entire novel gene was expressed in vitro in different heterologous systems: the PurePro Caulobacter crescentus expression system from where most of the characterization was attained, and also in the Escherichia coli BL-21 CodonPlus model for commercially potential purposes. The immunologic potential of ChaPs was determined with serum from naturally infected fish.

Jaime Figueroa - One of the best experts on this subject based on the ideXlab platform.

  • Protein-Based Vaccine Protect Against Piscirickettsia salmonis in Atlantic Salmon (Salmo salar)
    Frontiers in immunology, 2021
    Co-Authors: Juan Pablo Pontigo, Jaime Figueroa, Carla Espinoza, Mauricio Hernández, Guillermo Nourdin, Cristian Oliver, Ruben Avendaño-herrera, Cecilia Rauch, José M. Troncoso, Luis Vargas-chacoff
    Abstract:

    An effective and economical vaccine against the Piscirickettsia salmonis pathogen is needed for sustainable salmon farming and to reduce disease-related economic losses. Consequently, the aquaculture industry urgently needs to investigate efficient prophylactic measures. Three protein-based vaccine prototypes against Piscirickettsia salmonis were prepared from a highly pathogenic Chilean isolate. Only one vaccine effectively protected Atlantic salmon (Salmo salar), in correlation with the induction of Piscirickettsia-specific IgM antibodies and a high induction of transcripts encoding pro-inflammatory cytokines (i.e. Il-1β and TNF-α). In addition, we studied the proteome fraction protein of P. salmonis strain Austral-005 using multidimensional protein identification technology. The analyzes identified 87 proteins of different subcellular origins, such as the cytoplasmic and membrane compartment, where many of them have virulence functions. The other two prototypes activated only the innate immune responses, but did not protect Salmo salar against Piscirickettsia salmonis. These results suggest that the knowledge of the formulation of vaccines based on P. salmonis proteins is useful as an effective therapy, this demonstrates the importance of the different research tools to improve the study of the different immune responses, resistance to diseases in the Atlantic salmon. We suggest that this vaccine can help prevent widespread infection by P. salmonis, in addition to being able to be used as a booster after a primary vaccine to maintain high levels of circulating protective antibodies, greatly helping to reduce the economic losses caused by the pathogen.

  • protein based vaccine protect against Piscirickettsia salmonis in atlantic salmon salmo salar
    Frontiers in Immunology, 2021
    Co-Authors: Juan Pablo Pontigo, Jaime Figueroa, Carla Espinoza, Mauricio Hernández, Guillermo Nourdin, Cristian Oliver, Cecilia Rauch, José M. Troncoso, Ruben Avendanoherrera, Luis Vargaschacoff
    Abstract:

    An effective and economical vaccine against the Piscirickettsia salmonis pathogen is needed for sustainable salmon farming and to reduce disease-related economic losses. Consequently, the aquaculture industry urgently needs to investigate efficient prophylactic measures. Three protein-based vaccine prototypes against Piscirickettsia salmonis were prepared from a highly pathogenic Chilean isolate. Only one vaccine effectively protected Atlantic salmon (Salmo salar), in correlation with the induction of Piscirickettsia-specific IgM antibodies and a high induction of transcripts encoding pro-inflammatory cytokines (i.e., Il-1β and TNF-α). In addition, we studied the proteome fraction protein of P. salmonis strain Austral-005 using multidimensional protein identification technology. The analyzes identified 87 proteins of different subcellular origins, such as the cytoplasmic and membrane compartment, where many of them have virulence functions. The other two prototypes activated only the innate immune responses, but did not protect Salmo salar against P. salmonis. These results suggest that the knowledge of the formulation of vaccines based on P. salmonis proteins is useful as an effective therapy, this demonstrates the importance of the different research tools to improve the study of the different immune responses, resistance to diseases in the Atlantic salmon. We suggest that this vaccine can help prevent widespread infection by P. salmonis, in addition to being able to be used as a booster after a primary vaccine to maintain high levels of circulating protective antibodies, greatly helping to reduce the economic losses caused by the pathogen.

  • Transcriptional analysis of metabolic and virulence genes associated with biofilm formation in Piscirickettsia salmonis strains.
    FEMS microbiology letters, 2020
    Co-Authors: A Zúñiga, Alejandro J. Yáñez, C Cartes, D Haussmann, C Solis, G Nourdin, A. Alcaraz Romero, Jaime Figueroa
    Abstract:

    Piscirickettsia salmonis is a facultative intracellular bacterium that generates piscirickettsiosis affecting salmonids in Chile. The bacterium has the adaptability to survive in the marine environment under multiple stressful conditions. In this sense, this work focused on the analysis of a gene battery associated with biofilm formation under different culture conditions and on the adaptability of this biofilm to different media. The results indicated that the strains LF-89, IBM-034 and IBM-040 were strong biofilm producers, evidencing adaptability to the media by increasing the amount of biofilm through successive growths. Transcript levels of six genes described in various bacteria and P. salmonis, considered to have metabolic functions, and playing a relevant role in biofilm formation, were analyzed to evaluate bacterial functionality in the biofilm. The genes mazE-mazF, implicated in biofilm and stress, were markedly overexpressed in the biofilm condition in the three strains. For its part, gene gltA, an indicator of metabolic activity and related to virulence inhibition in Salmonella typhimurium, also seems to restrain the pathogenesis process in P. salmonis by inhibiting the expression of the virulence-associated genes liso and tcf. Finally, the expression of the glnA gene suggests the use of glutamine as an essential element for the growth of the biofilm.

  • Analysis of single nucleotide polymorphisms (SNPs) associated with antibiotic resistance genes in Chilean Piscirickettsia salmonis strains.
    Journal of fish diseases, 2019
    Co-Authors: Jaime Figueroa, Ruben Avendaño-herrera, Alejandro J. Yáñez, Adolfo Isla, C Cartes, F Lagos, D Castro, D Haussmann
    Abstract:

    The aetiological agent of Piscirickettsiosis is Piscirickettsia salmonis, a Gram-negative intracellular pathogen, and high doses of antibiotics have regularly been employed to treat this infection. Seven florfenicol and/or oxytetracycline resistance genes (tet pump, tetE, Tclor/flor, Tbcr, TfloR, ompF and mdtN) were identified in strains by in silico genome analyses. Later, the number of single nucleotide polymorphisms (SNPs) and its relationship with the resistance to these antibiotics were identified and analysed, using the original LF-89 strain as reference. Trials to determine and compare the minimum inhibitory concentration (MIC) of oxytetracycline and florfenicol in each strain, as well as to quantify the gPCR transcripts levels in the selected genes, were performed. Therefore, variations in the resistance to both antibiotics were observed, where the strain with fewer SNPs showed the highest susceptibility. Consistently, the in silico 3D analyses of proteins encoded by the selected genes revealed structural changes, evident in the sequences with the highest number of SNPs. These results showed that the bacterial resistance to oxytetracycline was mainly linked to the presence of SNPs in relevant sites, antibiotic resistance genes and an OmpF porin, leading to important changes in the protein structure.

  • Search and analysis of genes involved in antibiotic resistance in Chilean strains of Piscirickettsia salmonis.
    Journal of fish diseases, 2016
    Co-Authors: C Cartes, Alejandro J. Yáñez, Adolfo Isla, F Lagos, D Castro, M Muñoz, D Haussmann, Jaime Figueroa
    Abstract:

    Piscirickettsia salmonis is the pathogen causing Piscirickettsiosis. For treatment, the industry mainly uses oxytetracycline and florfenicol, so it is essential to understand the degree of susceptibility of this pathogen to these drugs. But this is still unknown for a large number of P. salmonis strains, as are the molecular mechanisms responsible for greater or lesser susceptibility. However, genes that confer resistance to these antimicrobials have been reported and characterized for this and other bacterial species, among which are membrane proteins that take out the drug. Our results identified differences in the degree of susceptibility to both antibiotics among different Chilean isolated of these bacteria. We analysed 10 available genomes in our laboratory and identified ~140 genes likely to be involved in antibiotic resistance. We analysed six specific genes, which suggests that some of them would eventually be relevant in conferring resistance to both antibiotics, as they encode for specific transporter proteins, which increase the number of transcripts when grown in media with these antibiotics. Our results were corroborated with EtBr permeability analysis, which revealed that the LF-89 strain accumulates this compound and has a reduced capacity to expulse it compared with the field strains.

P A Smith - One of the best experts on this subject based on the ideXlab platform.

  • Apoptosis inhibition of Atlantic salmon (Salmo salar) peritoneal macrophages by Piscirickettsia salmonis.
    Journal of fish diseases, 2017
    Co-Authors: S Díaz, M E Rojas, M Galleguillos, C Maturana, P I Smith, F Cifuentes, I Contreras, P A Smith
    Abstract:

    To improve the understanding of the piscirickettsiosis pathogenesis, the in vivo apoptosis modulation of peritoneal macrophages and lymphocytes was studied in juvenile Salmo salar intraperitoneally injected with Piscirickettsia salmonis. Five fish were sampled at post-exposure days 1, 5, 8 (preclinical), 20 (clinical) and 40 (post-clinical period of the disease), and the leucocytes of their coelomic washings were analysed by flow cytometry (using the JC-1 cationic dye), TUNEL and cytology to detect apoptotic cells. A selective and temporal pattern of apoptosis modulation by P. salmonis infection was observed. Apoptosis in lymphocytes was not affected, whereas it was inhibited in macrophages but only during the preclinical stage of the induced piscirickettsiosis. Hence, it is postulated that P. salmonis inhibits macrophage apoptosis at the beginning of the disease development to survive, multiply and probably be transported inside these phagocytes; once this process is complete, macrophage apoptosis is no longer inhibited, thus facilitating the exit of the bacteria from the infected cells for continuing their life cycle.

  • Short Communication Infectivity of Piscirickettsia salmonis in immersion-bath exposed rainbow trout Oncorhynchus mykiss (Walbaum) fry
    2016
    Co-Authors: P A Smith, M E Rojas, J R Contreras, A Guajardo, A Carbonero
    Abstract:

    Piscirickettsia salmonis is an obligate bacterial patho-gen which causes piscirickettsiosis, a systemic dis-ease affecting some anadromous and marine teleost fish species. To investigate the pathogenesis of this disease, a time-course study was conducted, using immunohistochemistry, after challenging rainbow trout Oncorhynchus mykiss (Walbaum) fry by an immersion bath with P. salmonis. To carry out this assay, fish (total n = 72; weight 2.5 g) were allotted to six subgroups (12 fish each) held in individual 50-L tanks sup-plied with a flow-through freshwater system (25 L h1) at 15.4 °C (SD 0.8). The SLGO-95 strain of P. salmonis (Smith et al. 1996b) was used. Bacteria, after thawing, were cul

  • Evidence of exotoxin secretion of Piscirickettsia salmonis, the causative agent of piscirickettsiosis.
    Journal of fish diseases, 2013
    Co-Authors: M E Rojas, M Galleguillos, S Díaz, A Machuca, Alfonso Carbonero, P A Smith
    Abstract:

    Piscirickettsia salmonis is the aetiological agent of piscirickettsiosis, a disease which affects a variety of teleost species and that is particularly severe in salmonid fish. Bacterial-free supernatants, obtained from cultures of three isolates of Piscirickettsia salmonis, were inoculated in Atlantic salmon, Salmo salar L., and in three continuous cell lines in an effort to determine the presence of secretion of extracellular products (ECPs) by this microorganism. Although steatosis was found in some liver samples, no mortalities or clinical signs occurred in the inoculated fish. Clear cytotoxicity was observed after inoculation in the cell lines CHSE-214 and ASK, derived from salmonid tissues, but not in MDBK, which is of mammalian origin. The degree of cytotoxicity of the ECPs was different among the P. salmonis isolates tested. The isolate that evidenced the highest cytotoxicity in its ECPs exhibited only an intermediate virulence level after challenging fish with bacterial suspensions of the three P. salmonis isolates. Almost complete inhibition of the cytotoxic activity of ECPs was seen after proteinase K treatment, indicating their peptidic nature, and a total preclusion of the cytotoxicity was shown after their incubation at 50 °C for 30 min. Results show that P. salmonis can produce ECPs and at least some of them are thermolabile exotoxins that probably play a role in the pathogenesis of piscirickettsiosis.

  • Culture of Piscirickettsia salmonis on enriched blood agar.
    Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians Inc, 2008
    Co-Authors: Michael J. Mauel, Cynthia Ware, P A Smith
    Abstract:

    Piscirickettsia salmonis is the etiologic agent of piscirickettsiosis, an economically significant disease of fish. Isolation of P. salmonis by culturing on fish cell lines has been the standard technique since the initial isolation of the organism. The ability to grow P. salmonis on artificial media would relieve facilities of the cost of maintaining cell lines, permit isolation at fish culture sites with fewer contamination problems, and allow easier transport of isolates to diagnostic facilities for confirmation assays. This report describes the successful culture of P. salmonis on enriched blood agar.

  • Experimental infection of coho salmon Oncorhynchus kisutch by exposure of skin, gills and intestine with Piscirickettsia salmonis
    Diseases of aquatic organisms, 2004
    Co-Authors: P A Smith, M E Rojas, J. Contreras, A Guajardo, M. A. Morales, J Larenas
    Abstract:

    Piscirickettsiosis pathogenesis was examined using some tissues as entry portals of Piscirickettsia salmonis in coho salmon. Juvenile fish, weighing approximately 8.4 g, were used in this trial. Inocula were prepared using the strain SLGO-95 of P. salmonis. The micro-organism was cultured in the CHSE-214 cell line as described by Fryer et al. (1990) and doses containing 10 4.7 and 10 3.7 TCID50 were prepared. Each dose was used to infect the fish via skin, gills and intestine. Skin and gills were exposed by calibrated drops, and the intestine by an intubation through the anal opening. Some fish were injected intraperitoneally with the same P. salmonis doses, as positive virulence controls. Sham-inoculated fish for each of the tested routes were also included as negative controls. Piscirickettsiosis was experimentally reproduced with all the inoculation methods. Cumula- tive mortalities and survival analyses showed that the most effective entry portal was skin followed by intestinal intubation and finally by gill infection.

Fernando Bustamante - One of the best experts on this subject based on the ideXlab platform.

  • prevalence geographic distribution and phenotypic differences of Piscirickettsia salmonis em 90 like isolates
    Journal of Fish Diseases, 2017
    Co-Authors: José Saavedra, Harry Bohle, Patricio Henríquez, Horst Grothusen, Esteban Navas, N. Hernandez, A Osses, A Castillo, A Cancino, Fernando Bustamante
    Abstract:

    Early reports accounted for two main genotypes of Piscirickettsia salmonis, a fish pathogen and causative agent of piscirickettsiosis, placing the single isolate EM-90 apart from the prototypic LF-89 and related isolates. In this study, we provide evidence that, contrary to what has been supposed, the EM-90-like isolates are highly prevalent and disseminated across Chilean marine farms. Molecular analysis of 507 P. salmonis field isolates derived from main rearing areas, diverse hosts and collected over 6 years, revealed that nearly 50% of the entire collection were indeed typed as EM-90-like. Interestingly, these isolates showed a marked host preference, being recovered exclusively from Atlantic salmon (Salmo salar) samples. Although both strains produce undistinguishable pathological outcomes, differences regarding growth kinetics and susceptibility to the antibiotics and bactericidal action of serum could be identified. In sum, our results allow to conclude that the EM-90-like isolates represent an epidemiologically relevant group in the current situation of piscirickettsiosis. Based on the consistency between genotype and phenotype exhibited by this strain, we point out the need for genotypic studies that may be as important for the Chilean salmon industry as the continuous surveillance of antimicrobial susceptibility patterns.

  • The Genome Sequence of an Oxytetracycline-Resistant Isolate of the Fish Pathogen Piscirickettsia salmonis Harbors a Multidrug Resistance Plasmid.
    Genome announcements, 2017
    Co-Authors: Harry Bohle, Patricio Henríquez, Horst Grothusen, Esteban Navas, Fernando Bustamante, Patricio Bustos, Marcos Mancilla
    Abstract:

    ABSTRACT The amount of antibiotics needed to counteract frequent piscirickettsiosis outbreaks is a major concern for the Chilean salmon industry. Resistance to antibiotics may contribute to this issue. To understand the genetics underlying Piscirickettsia salmonis-resistant phenotypes, the genome of AY3800B, an oxytetracycline-resistant isolate bearing a multidrug resistance plasmid, is presented here.

  • Prevalence, geographic distribution and phenotypic differences of Piscirickettsia salmonis EM‐90‐like isolates
    Journal of fish diseases, 2017
    Co-Authors: José Saavedra, Harry Bohle, Patricio Henríquez, Horst Grothusen, Esteban Navas, N. Hernandez, A Osses, A Castillo, A Cancino, Fernando Bustamante
    Abstract:

    Early reports accounted for two main genotypes of Piscirickettsia salmonis, a fish pathogen and causative agent of piscirickettsiosis, placing the single isolate EM-90 apart from the prototypic LF-89 and related isolates. In this study, we provide evidence that, contrary to what has been supposed, the EM-90-like isolates are highly prevalent and disseminated across Chilean marine farms. Molecular analysis of 507 P. salmonis field isolates derived from main rearing areas, diverse hosts and collected over 6 years, revealed that nearly 50% of the entire collection were indeed typed as EM-90-like. Interestingly, these isolates showed a marked host preference, being recovered exclusively from Atlantic salmon (Salmo salar) samples. Although both strains produce undistinguishable pathological outcomes, differences regarding growth kinetics and susceptibility to the antibiotics and bactericidal action of serum could be identified. In sum, our results allow to conclude that the EM-90-like isolates represent an epidemiologically relevant group in the current situation of piscirickettsiosis. Based on the consistency between genotype and phenotype exhibited by this strain, we point out the need for genotypic studies that may be as important for the Chilean salmon industry as the continuous surveillance of antimicrobial susceptibility patterns.

  • Comparative Genome Analysis of Two Isolates of the Fish Pathogen Piscirickettsia salmonis from Different Hosts Reveals Major Differences in Virulence-Associated Secretion Systems.
    Genome announcements, 2014
    Co-Authors: Harry Bohle, Patricio Henríquez, Horst Grothusen, Esteban Navas, Fernando Bustamante, Patricio Bustos, Alvaro Sandoval, Marcos Mancilla
    Abstract:

    ABSTRACT Outbreaks caused by Piscirickettsia salmonis are one of the major threats to the sustainability of the Chilean salmon industry. We report here the annotated draft genomes of two P. salmonis isolates recovered from different salmonid species. A comparative analysis showed that the number of virulence-associated secretion systems constitutes a main genomic difference.