Search

Las algas rojas se han considerado como una fuente importante de polisacáridos con propiedades inmunomodulatorias potenciales. Los polisacáridos de la pared celular del alga roja Porphyridium cruentum pueden componer más de 50% de su biomasa; sin embargo, poco se sabe sobre su composición bioquímica y sus propiedades inmunomoduladoras. Consecuentemente, el objetivo de este estudio fue evaluar el efecto de los polisacáridos de P. cruentum sobre la producción del factor de necrosis tumoral-α (TNF-α, de interleucina-6 (IL-6) y de óxido nítrico (NO). Los polisacáridos de P. cruentum se extrajeron y purificaron mediante una precipitación con bromuro de N-cetilpiridinio, y se caracterizaron por espectroscopía infrarroja con transformada de Fourier. El efecto de la actividad de la línea celular de macrófagos murinos RAW 264.7 fue examinada mediante una cuantificación de la producción de TNF-α, IL-6 y NO utilizando un ensayo por inmunoabsorción ligado a enzimas. Los resultados mostraron que los polisacáridos de P. cruentum indujeron la acumulación de TNF-α e IL-6. La producción de TNF-α fue significativamente más alta que la observada en el control (lipopolisacárido bacteriano, LPS) cuando la concentración de polisacáridos fue mayor a 6.25 μg mL-1. El añadir niveles de polisacáridos arriba de 25 μg mL-1 produjó niveles de IL-6 que fluctuaron entre 3.4 y 4 ng mL-1, lo cual fue similar a la producción de IL-6 inducida con 50 ng mL-1 de LPS (3.3± 0.3). En contraste a IL-6 y TNF-α, la producción de NO sólo fue detectada cuando las concentraciones de polisacáridos fueron mayores que 25 μg mL-1. Estos resultados indican por primera vez que los polisacáridos de P. cruentum inducen activamente la producción de citoquinas. [ABSTRACT FROM AUTHOR]

The article provides information on the study concerning the susceptibility of Photobacterium damselae subspecies piscicida strains to several antibacterial agents in Great Britain. The author infers that the diseases of bacterial origin are likely the most substantial cause of economic losses in the aquaculture industry. Moreover, antibiotic treatment of bacterial diseases affecting farmed fish has been used for years. Photobacterium damselae subspecies piscicida is a fish pathogen responsible for significant losses in fish aquaculture worldwide.

Most studies carried out to select microorganisms as candidate probiotics have focused onin vitroantagonism tests, such as the production of inhibitory compounds against pathogenic microorganisms. However, attachment to mucous surfaces could be another criterion to be considered when selecting potential probiotics for aquaculture. Nineteen isolates obtained from farmed Senegalese sole,Solea senegalensisKaup, and gilthead sea bream,Sparus aurataL., have been evaluated for their capacity to adhere to skin and intestinal mucus of Senegalese sole, and their antagonistic effect againstPhotobacterium damselaesubsp.piscicida, an important pathogen for farmed sole. The isolates from gilthead sea bream showed the highest percentage of adhesion to sole mucus, whilst the pathogenic microorganisms assayed and the isolates from sole showed, in general, a lower ability to adhere to sole mucus. The results suggest that the adhesion to fish mucus was more dependent on the isolate tested than on the host mucus. The isolates from gilthead sea bream also showed a higher antagonistic activity againstP. damselaesubsp.piscicidathan those from Senegalese sole. Four isolates were selected, on the basis of their adhesive ability and antagonistic effect onP. damselaesubsp.piscicida, to study their interactions with the pathogen in respect of adhesion to skin and intestinal mucus under exclusion, competition and displacement conditions. The results obtained show the ability of three isolates to reduce the adhesion ofP. damselaesubsp.piscicidato sole mucus under displacement and competition conditions. The adhesion of the pathogen to sole intestinal mucus was also significantly reduced when three isolates were assayed under exclusion conditions. [ABSTRACT FROM AUTHOR]

The kinetics of adhesion of Listonella anguillarum cells to skin, intestinal and gill mucus suspensions of gilt-head seabream was studied. A Langmuir adsorption isotherm was calculated, and the results obtained indicated that this microorganism showed a saturation kinetics. The pretreatment of the mucus suspensions with a surface extract obtained from L. anguillarum cells promoted a very important inhibition of the number of adhered bacteria to the different mucus suspensions. The potential role of surface structures on the adhesion of L. anguillarum to mucus of gilt-head seabream is discussed. [ABSTRACT FROM AUTHOR]

Discusses the survival of photobacterium damselae subsp. piscicida against hydrogen peroxide under different culture conditions. Increased levels of catalase activity; Percentage of colony forming units recovered compared with untreated samples; Increase rates of survival of the non-virulent strain; Effect of iron in the culture on survival.

An abstract of the article "Biofiltration of Fishpond Effluents by Using Macroalgae and the Use Algal Biomass As Functional Feed," by R. M. Rico and colleagues is presented.

Pleuronectiforms are an important group of fish, and one of their species, Solea senegalensis (Kaup 1858), has been extensively studied at different levels, although information about its intestinal microbiota and the effects of different factors on it is very scarce. Modern aquaculture industry demands strategies which help to maintain a microbiologically healthy environment and an environmentally friendly aquaculture. In this context, probiotics seem to offer an attractive alternative. The intake of probiotics could modify the composition of the intestinal microbiota, which is a key component in excluding potential invaders and maintaining health. The aim of this study was to evaluate by 16S rRNA gene analysis using polymerase chain reaction-denaturing gradient gel electrophoresis the effect of administering fresh or lyophilized cells of Pdp11 on the intestinal microbiota of farmed Senegalese sole, using sodium alginate to facilitate the incorporation of bacterial cells to the feed. The results obtained showed that the composition of fish intestinal microbiota was affected when fish received a diet supplemented with sodium alginate and fresh or lyophilized probiotic cells. In all cases, the dominant bacterial groups belonged to γ-Proteobacteria and mainly the Vibrio species. The use of sodium alginate reduced the incidence of populations with <97% 16S rRNA gene sequence identity to uncultured microorganisms in the intestinal microbiota until non-detected limits. On the other hand, the supplementation of the diet with probiotics produced an increase of the predominant species related to Vibrio genus.

The in vitro effects of four heat-inactivated bacterial species on the cellular innate immune responses of the gilthead seabream (Sparus aurata L.) were investigated. Head-kidney leucocytes were isolated and incubated for 30 min with two bacteria isolated from seabream skin (Pdp11 and 51M6; members of the Vibrionaceae and in the genus Shewanella) and two bacteria used as probiotics in humans and cattle (Lactobacillus delbrüeckii subsp. lactis and Bacillus subtilis) at 5 x 10(5), 5 x 10(6) or 5 x 10(7)CFU/ml. After incubation, different cellular innate immune parameters (leucocyte peroxidase content, phagocytosis, respiratory burst activity and cytotoxicity) were evaluated. The leucocyte peroxidase content was significantly higher after incubation with 51M6 at 5 x 10(7)CFU/ml. Head-kidney phagocytes were able to engulf the four bacterial species in all four cases, L. delbrüeckii subsp. lactis and B. subtilis being the most actively phagocytized. The incubation of seabream leucocytes with 51M6, L. delbrüeckii subsp. lactis and B. subtilis resulted in a great increase in respiratory burst activity. Cytotoxic activity was generally stimulated in a dose-dependent manner, the enhancement obtained with 5 x 10(7)CFU/ml being statistically significant. The usefulness of in vitro assays for screening and selecting candidate probiotic bacteria, as well as for optimising their effective dose, is discussed in relation with their immune-modulatory properties.

The effects of the dietary administration of two heat-inactivated whole bacteria from the Vibrionaceae family, singly or combined, on innate immune response of the seabream were studied. The two bacteria (Pdp11 and 51M6), which were obtained from the skin of gilthead seabream, showed in vitro characteristics that suggested they could be considered as potential fish probiotics. The fish were fed four different diets: control (non-supplemented), or diets supplemented with heat-inactivated bacteria at 10(8) cfu g(-1) Pdp11, 10(8) cfu g(-1) 51M6 or with 0.5 x 10(8) cfu g(-1) Pdp11 plus 0.5 x 10(8) cfu g(-1) 51M6 for 4 weeks. Six fish were sampled at weeks 1, 2, 3 and 4, when the main humoral (natural haemolytic complement activity and serum peroxidase content) and cellular innate immune responses (leucocyte peroxidase content, phagocytosis, respiratory burst and cytotoxicity) were evaluated. The serum peroxidase content and the natural haemolytic complement activity increased with time, reaching the highest values in the third and fourth weeks of feeding, respectively. The phagocytic ability of specimens fed the mixture of the two inactivated bacteria was significantly higher than in the controls after 2 and 3 weeks of treatment. The same activity increased significantly in seabream fed the Pdp11 diet for 2 weeks or the 51M6 diet for 3 weeks. Respiratory burst activity was unaffected by all the experimental diets at all times assayed. Cytotoxic activity had significantly increased after 3 weeks in fish fed the 51M6 diet. These results are discussed in terms of the usefulness of incorporating inactivated probiotic bacteria into fish diets.