Estacion de Investigaciones Hidrobiologicas de Guayana

La Salle, Venezuela

Estacion de Investigaciones Hidrobiologicas de Guayana

La Salle, Venezuela
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Bastardo A.,University of Santiago de Compostela | Ravelo C.,Estacion de Investigaciones Hidrobiologicas de Guayana | Romalde J.L.,University of Santiago de Compostela
Veterinary Microbiology | Year: 2012

A polyphasic analysis was carried out on Yersinia ruckeri strains isolated from recently outbreaks in vaccinated fish using a combination of different phenotypic and molecular typing methods in order to study their variability and epidemiological relationships. Eighty strains were subjected to biotyping with conventional tests and API 20E system, serotyping, outer membrane protein (OMP) and lipopolysaccharide (LPS) profiling, and genetic fingerprinting by ERIC-PCR and REP-PCR techniques. The strains showed a high diversity, as evidenced by the formation of different phenotypic groups mainly related to the serotypes, LPS and OMP profiles. The diversity among all isolates, calculated as Simpson's diversity index (Di), varied between 0.35 (REP-PCR) and 0.70 (OMP). The most discriminative values (Di value ≥0.86) were obtained from any combination of three methods including biotype, serotype, API 20E profile, LPS or OMP. With the combination of all typing methods used a Di value of 0.90 was obtained. Association between different groups to the host species was evidenced. Furthermore, it seems that strains with similar characteristics are associated with recent outbreaks occurred in vaccinated fish in certain geographical areas. Our results emphasize the usefulness of using a combination of several different typing methods for epidemiological and bacterial diversity studies. © 2012 Elsevier B.V.


Bastardo A.,University of Santiago de Compostela | Sierralta V.,National Major San Marcos University | Leon J.,National Major San Marcos University | Ravelo C.,Estacion de Investigaciones Hidrobiologicas de Guayana | Romalde J.L.,University of Santiago de Compostela
Aquaculture | Year: 2011

A total of 30 strains of Yersinia ruckeri causing recent outbreaks in Peruvian trout culture systems, were studied by means of biochemical characteristics, serology, lipopolysaccharide (LPS) and outer membrane protein (OMP) analysis, and ERIC and REP PCR fingerprinting. All the Peruvian isolates were found to be fermentative, oxidase negative and positive for decarboxylation of lysine and ornithine and utilization of glucose and mannitol, allowing their presumptive identification as Y. ruckeri. Sequencing of the 16S rRNA gene confirmed that isolates were indeed Y. ruckeri (>99.98% identity). Although most of the strains studied were motile and lipase positive corresponding to the biotype 1 of Y. ruckeri, 5 of these strains were negative from both tests, being identified as biotype 2. In addition, drug susceptibility tests determined high sensitivity to sulfamethoxazole/trimethoprim, oxytetracycline, ampicillin and enrofloxacin in all the isolates. Serologically, all the Peruvian strains studied were identified as belonging to the serotype O1 subgroup a. Analysis of the lipopolysaccharide (LPS) as well as total and outer membrane proteins (OMPs) profiles and the correspondent inmunoblotting, supported these results. Genotyping performed by means of ERIC- and REP-PCR determined major correlation of the Peruvian isolates with the type strain NCIMB 2194T regardless of the biotype. © 2011 Elsevier B.V.


Bastardo A.,University of Santiago de Compostela | Bohle H.,ADL Diagnostic Chile Ltd | Ravelo C.,Estacion de Investigaciones Hidrobiologicas de Guayana | Toranzo A.E.,University of Santiago de Compostela | Romalde J.L.,University of Santiago de Compostela
Diseases of Aquatic Organisms | Year: 2011

We investigated 11 strains of Yersinia ruckeri, the causative agent of enteric redmouth disease (ERM), that had been isolated from Atlantic salmon Salmo salar L. farmed in Chile and previously vaccinated against ERM. Phylogenetic analysis of the 16S rRNA gene sequences confirmed the identification of the salmon isolates as Y. ruckeri. A comparative analysis of the biochemical characteristics was made by means of traditional and commercial miniaturised methods. All studied isolates were motile and Tween 80 positive, and were identified as biotype 1. In addition, drug susceptibility tests determined high sensitivity to sulphamethoxazole/trimethroprim, oxytetracycline, ampicillin and enrofloxacin in all isolates. Serological assays showed the presence of O1a, O1b and O2b serotypes, with a predominance of the O1b serotype in 9 strains. Analysis of the lipopolysaccharide profiles and the correspondent immunoblot confirmed these results. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of the outer membrane proteins revealed that all Chilean strains had profiles with a molecular weight range between 34 and 55 kDa, with 3 distinct groups based on differences in the major bands. Genotyping analyses by enterobacterial repetitive intergenic consensus (ERIC-) and repetitive extragenic palindromic (REP-)PCR techniques clearly indicated intraspecific genetic diversity among Chilean Y. ruckeri strains. © Inter-Research 2011.


Winemiller K.O.,Texas A&M University | Montana C.G.,Texas A&M University | Montana C.G.,North Carolina State University | Roelke D.L.,Texas A&M University | And 8 more authors.
Ecological Monographs | Year: 2014

Variable hydrology of rivers strongly affects biophysical factors that influence primary production and population densities, thereby affecting the relative influence of bottom-up and top-down processes in trophic networks. Many tropical floodplain rivers have sustained seasonal flood pulses driven by precipitation patterns of the Intertropical Convergence Zone. These changes in flow alter concentrations of dissolved nutrients, aquatic primary productivity, and per-unit-area densities of aquatic organisms. Therefore, one would predict that the strength of top-down effects of animals on basal resources should shift as the annual flood pulse progresses. We conducted a series of field experiments in a Neotropical lowland river to test for effects of hydrologic phase, habitat (in-channel vs. floodplain aquatic habitat), and benthic-feeding fish and meiofauna on particulate organic matter, chlorophyll, and benthic microalgae. Net ecosystem productivity of this oligotrophic river is higher during the low phase of the annual flood cycle, which is also when resident fishes are at highest densities and there is a seasonal influx of migratory benthic-feeding fish. We therefore hypothesized that top-down effects of benthic-feeding fish would fluctuate temporally, with strongest effects during low water levels. We found that fish controlled the abundance of particulate organic matter and algae on solid substrates, but not on sand, during falling- and low-water phases within both channel and floodplain habitats. Except for diatom assemblages, which responded to fish exclusion, the taxonomic structure of algal and meiofauna assemblages was not significantly influenced by fish-exclusion treatments, but varied in relation to habitat type and hydrologic phase. Meiofauna densities were highest during the low-water period; experimental exclusion of meiofauna during this period had a significant effect on accumulation of particulate organic matter in sand. By controlling abundance of important basal resources, fishes and meiofauna have a large potential to influence other components of this tropical ecosystem. Our findings emphasize the predictable, gradual, changes in consumer-resource interactions associated with the seasonal flood pulse in tropical river systems. © 2014 by the Ecological Society of America.


Mora A.,Venezuelan Institute for Scientific Research | Pisapia D.,Estacion de Investigaciones Hidrobiologicas de Guayana | Gonzalez N.,Estacion de Investigaciones Hidrobiologicas de Guayana | Handt H.,Venezuelan Institute for Scientific Research | And 4 more authors.
Water, Air, and Soil Pollution | Year: 2015

This paper identifies the effects of red mud spills on several lagoons of the Orinoco River located surrounding the red mud deposits. Chemical and mineralogical analyses of sediments indicate that the geochemical signature of red mud is evident in Los Caribes and Guadita lagoons, with elevated concentrations of Fe, Al, and Na and the presence of goethite and hematite as the major mineral phases. Water quality analyses indicate that these lagoons have elevated values of dissolved oxygen, pH, conductivity, and dissolved Ca, Na, Ni, and Al. Also, elevated concentrations of Ca, Mg, and Mn in sediments suggest the precipitation of calcite, brucite a Mn-oxyhydroxides due to high pH values. Although Los Cardonales lagoon also showed evidence of red mud deposition, the enrichment of Mn, Zn, Ni, and Cd in sediments from this lagoon could be associated with wastewaters coming from landfills. The absence of vascular plants and the low abundance of fish communities in several lagoons can be related with the high pH values and the elevated concentrations of dissolved Al. The high concentrations of Fe and Mn in sediments of these lagoons can have adverse effects on benthic organisms, according to International Guidelines. Even though this lagunar system is impacted by red mud spills, hyperalkaline conditions (pH∈>∈13) were not found in superficial waters. Thus, dissolved trace element concentrations (Fe, Zn, Mn, Cr, Cu, Cd, and Pb) in waters were not high, mainly due to trace elements are immobilized by sorption or coprecipitation at circum-neutral pH. © 2015 Springer International Publishing Switzerland.


Bastardo A.,University of Santiago de Compostela | Ravelo C.,Estacion de Investigaciones Hidrobiologicas de Guayana | Castro N.,University of Santiago de Compostela | Calheiros J.,Quinta do Salmao | Romalde J.L.,University of Santiago de Compostela
Fish and Shellfish Immunology | Year: 2012

Lactococcus garvieae and Aeromonas hydrophila are bacterial pathogens affecting salmonids and other fish species and cause of heavy losses in aquaculture. Diseases caused by these bacteria can be controlled satisfactory by immunization using monovalent vaccines. In this study, the protective efficacy of two bivalent vaccines against L. garvieae and A. hydrophila was evaluated in rainbow trout (Oncorhynchus mykiss). Bivalent formulations, containing formalin-inactivated bacteria, were prepared as an aqueous bacterin and as an adjuvanted vaccine using montanide ISA-763. Protection against L. garvieae and A. hydrophila was tested at day 30 and 90 post-vaccination. High levels of protection were achieved for the aqueous and adjuvanted bivalent vaccines against L. garvieae (RPS of 100% and 95.3%) and A. hydrophila (RPS of 100% and 95.3%) at day 30 post-vaccination. Significant differences (p < 0.05) were found between the RPS at days 30 and 90 post-immunization with a decrease in the protection levels for the aqueous bivalent vaccine against L. garvieae (RPS 76.2%) and A. hydrophila (RPS 85%), but not for the adjuvanted vaccine (RPS of 90% against L. garvieae and 95% against A. hydrophila). In addition, high antibody levels were observed in the vaccinated fish at day 15 post-immunization using both vaccines. Our results demonstrate that these bivalent vaccines can effectively protect rainbow trout against L. garvieae and A. hydrophila and could offer an appropriate strategy to prevent these infections in rainbow trout farms. © 2012 Elsevier Ltd.


Bastardo A.,University of Santiago de Compostela | Ravelo C.,Estacion de Investigaciones Hidrobiologicas de Guayana | Romalde J.L.,University of Santiago de Compostela
Environmental Microbiology | Year: 2012

Yersinia ruckeri is the causative agent of enteric redmouth in fish and one of the major bacterial pathogens causing losses in salmonid aquaculture. Previously typing methods, including restriction enzyme analysis, pulsed-field gel electrophoresis and multilocus enzyme electrophoresis (MLEE) have indicated a clonal population structure. In this work, we describe a multilocus sequence typing (MLST) scheme for Y. ruckeri based on the internal fragment sequence of six housekeeping genes. This MLST scheme was applied to 103 Y. ruckeri strains from diverse geographic areas and hosts as well as environmental sources. Sequences obtained from this work were deposited and are available in a public database. Thirty different sequence types (ST) were identified, 21 of which were represented by a single isolate, evidencing high genetic diversity. ST2 comprised more than one-third of the isolates and was most frequently observed among isolates from trout. Two major clonal complexes (CC) were identified by eBURST analysis showing a common evolutionary origin for 94 isolates forming 21 STs into CC1 and for 6 isolates of 6 STs in the CC2. It was also possible to associate some unique ST with isolates from recent outbreaks in vaccinated salmonid fish. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.


Bastardo A.,University of Santiago de Compostela | Ravelo C.,Estacion de Investigaciones Hidrobiologicas de Guayana | Romalde J.L.,University of Santiago de Compostela
Applied Microbiology and Biotechnology | Year: 2012

Yersinia ruckeri is the causative agent of enteric redmouth diseases (ERM) and one of the major bacterial pathogens causing losses in salmonid aquaculture. Since recent ERM vaccine breakdowns have been described mostly attributed to emergence of Y. ruckeri biotype 2 strains, rapid, reproducible, and sensitive methods for detection are needed. In this study, a real-time polymerase chain reaction (PCR) primer/probe set based on recombination protein A (recA) gene was designed and optimized to improve the detection of Y. ruckeri. The primer/probe set proved to have a 100 % analytical specificity and a sensitivity of 1.8 ag μl-1, equivalent to 1.7 colony-forming units (CFU) ml-1, for purified DNA, 3.4 CFU g-1 for seeded liver, kidney, and spleen tissues, and 0.34 CFU/100 μl-1 for seeded blood, respectively. The assay was highly reproducible with low variation coefficient values for intra- and interrun experiments (2.9 % and 9.5 %, respectively). Following optimization, the assay was used to detect changes in the bacterial load during experimental infection. Rainbow trout (Onchorhynchus mykiss) were exposed to two strains of Y. ruckeri (biotype 1 and biotype 2) by intraperitoneal inoculation. Internal organs (liver, kidney, spleen) and blood were biopsied from dead fish daily for 15 days to quantify copies of pathogen DNA per gram of tissue. The findings showed the efficacy of this real-time PCR assay to quantify Y. ruckeri cells in the fish tissues and also confirmed this assay as a non-lethal method for the detection of this pathogen in blood samples. © Springer-Verlag 2012.


Bastardo A.,University of Santiago de Compostela | Ravelo C.,Estacion de Investigaciones Hidrobiologicas de Guayana | Romalde J.L.,University of Santiago de Compostela
Frontiers in Microbiology | Year: 2015

Phylogeographic patterns and population genetic structure of Yersinia ruckeri, the pathological agent of enteric redmouth disease (ERM) in salmonids, were investigated on the basis of concatenated multiloci sequences from isolates of different phenotypes obtained between 1965 and 2009 from diverse areas and hosts. Sequence analyses revealed genetic differentiation among subpopulations with the largest genetic distance occurring between subpopulations of Europe and Canada and/or South America. Bayesian analysis indicated the presence of three ancestral population clusters. Mismatch distribution displayed signatures characteristic of changes in size due to demographic and spatial expansions in the overall Y. ruckeri population, and also in the geographically separate subpopulations. Furthermore, a weak signal of isolation by distance was determined. A significant positive correlation between genetic and geographical distances was observed. These results revealed that the population of Y. ruckeri has undergone both ancient and recent population changes that were probably induced by biogeography forces in the past and, much more recently, by adaptive processes forced by aquaculture expansion. These findings have important implications for future studies on Y. ruckeri population dynamics, on the potential role of genetic structure to explain variations in ERM transmission, and on the effect of past evolutionary events on current estimations of gene flow. © 2015 Bastardo, Ravelo and Romalde.


PubMed | Estacion de Investigaciones Hidrobiologicas de Guayana and University of Santiago de Compostela
Type: | Journal: Frontiers in microbiology | Year: 2015

Phylogeographic patterns and population genetic structure of Yersinia ruckeri, the pathological agent of enteric redmouth disease (ERM) in salmonids, were investigated on the basis of concatenated multiloci sequences from isolates of different phenotypes obtained between 1965 and 2009 from diverse areas and hosts. Sequence analyses revealed genetic differentiation among subpopulations with the largest genetic distance occurring between subpopulations of Europe and Canada and/or South America. Bayesian analysis indicated the presence of three ancestral population clusters. Mismatch distribution displayed signatures characteristic of changes in size due to demographic and spatial expansions in the overall Y. ruckeri population, and also in the geographically separate subpopulations. Furthermore, a weak signal of isolation by distance was determined. A significant positive correlation between genetic and geographical distances was observed. These results revealed that the population of Y. ruckeri has undergone both ancient and recent population changes that were probably induced by biogeography forces in the past and, much more recently, by adaptive processes forced by aquaculture expansion. These findings have important implications for future studies on Y. ruckeri population dynamics, on the potential role of genetic structure to explain variations in ERM transmission, and on the effect of past evolutionary events on current estimations of gene flow.

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