Papel de las actividades superóxido dismutasa y catalasa en la ...

most efficient probiotics for aquaculture, as a consequence of the specificity of aquatic
microbiota [8]. Hence, we assessed the probiotic potential of bacteria of the genus
Shewanella, naturally present on seabream skin [36]. Moreover, the selection of the
probiotic Pdp11 was based on its adhesion to intestinal mucus, its resistance to intestinal
mucus and bile [37, 38] and its ability to increase several immunological parameters in
gilthead seabream [27, 29].
Despite of their affiliation within the same genus, Shewanella, and same origin of
both microorganisms assayed in this study, their effect on the respiratory burst activity
was completely different, as only Pdp11 strain produced statistically significant increase
in superoxide anion production by sole kidney phagocytes. This could suggest that the
immunostimulation of the respiratory burst of sole phagocytes is strain-dependent rather
than a general characteristic of a bacterial species. This strain-dependence has been
described for other characteristics such as the mucus adhesion of certain isolates of
lactic acid bacteria [56] and fish isolates [37, 38]. In a previous work it was reported
that Pdp11 strain did not induce an increase on the respiratory burst activity of
phagocytes from gilthead seabream when the microorganism was administered heatinactivated
[27]. These results are in agreement with Panigrahi et al. [24], who indicated
that probiotic viability could probably influence the induced immune responses. It was
found that viable lactic acid bacteria were more efficient in enhancing certain aspects of
immune response in rainbow trout (Oncorhynchus mykiss) compared to non-viable heatkilled
cells, although the respiratory burst activity in this case, was not affected.
Although several authors reported the induction of respiratory burst activity by
probiotics [23, 57-59]. The fact that the potential probiotic strain Pdp13 did not increase
superoxide anion production does not rule out that the possibility to induce a significant
change in other immunological parameters. This is supported by the fact that we
observed increased survival after the challenge with the pathogenic bacteria P. damselae
subsp. piscicida in fish fed with diet supplemented with Pdp13 strain, compared to
control fish (fed with normal diet) and fish fed with the diet supplemented with Pdp11.
Although the degree of protection achieved with Pdp13 was not very high (i.e. 20%
survival), the reduced and retarded mortality might provide additional time that could be
useful to prevent the infection by using other different treatments.
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