Probiotic Applications in Temperate and Warm Water Fish Species - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 261

immunostimulatory effects after combined oral administration. This was possibly due to the
close phylogenetic relationship between the two bacteria assayed and thus no complementary
effect was attained. However, both heat-inactivated bacterial species were capable of modulat-
ing the sea bream innate immune system, showing their potential to induce immune responses
probably with the recognition by mucosal cells of bacterial antigens or other surface bound
structures rather than a host response against probiotic metabolic products or active participa-
tion of the probiont in the interactions with the epithelial surface. In fact in a following study,
Salinas et al . (2008) demonstrated that heat-inactivated Lb. delbrueckii subsp. lactis and B.
subtilis applied via the diet to gilthead sea bream induced effects on the systemic humoral and
cellular innate immune system as well as on local cellular defences in the gut, confirming that
an active participation by the probiont is not always necessary. To assess whether or not the
bacterial strains or their origin were related to the immunomodulatory properties of probiotics,
Salinas and colleagues (2006) conducted a further study assaying the in vitro immunostimula-
tory properties of four heat-inactivated bacterial species: Sh. putrefaciens Pdp11, Shewanella
sp. 51M6, Lb. delbrueckii subsp . lactis and B. subtilis . The analysis of the individual bacte-
rial species revealed a similar in vitro immunostimulatory effect for all the studied strains,
which was strongly related to the bacterial concentration, confirming that the use of appropri-
ate bacterial concentrations and administration times is critical to achieve the desired effect on
the immune system in aquacultured fish. In addition to the studies on the juvenile and adult
sea bream immune system, Picchietti et al . (2007) assessed the potential immunomodulatory
properties of lactobacilli ( Lb. fructivorans AS17B and Lb. plantarum ) on the developing sea
bream immune system to evaluate the beneficial effects of microbial products on larval intesti-
nal immunity. In particular, the work demonstrated that probiotic applications could increase
the density of Ig + cells (Figure 10.1A), total acidophilic granulocytes (Figure 10.1B-D) and
in particular a subpopulation of acidophilic granulocytes (shown to be phagocytic against V.
anguillarum ) (Chaves-Pozo et al . 2005) in the gut of sea bream. However, these effects were
dependent on the larval age and/or the duration of the treatment.
The modulation of the intestinal microbiota and immune system of gilthead sea bream
was also evaluated following the probiotic administration of the yeast Debaromyces hansenii
L2 both singly (Reyes-Becerril et al . 2012) or in conjunction with inulin (Tapia-Paniagua
et al. 2011). In these studies, changes in the intestinal microbiota in fish receiving the supple-
mented diet were detected. These changes coincided with an up-regulation of the expression
of immunological genes in the skin and HK at 2 and 4 weeks, respectively (Tapia-Paniagua
et al . 2011; Reyes-Becerril et al . 2012). In addition, Romàn and colleagues (2012) evalu-
ated the in vitro effects of the probiotic Vagococcus fluvialis, on sea bream leukocytes. In
particular Vagococcus fluvialis, , both live and inactivated, produced dose-dependent incre-
ments of respiratory burst activity in sea bream leukocytes as previously described by Salinas
et al. (2006) after treatment with four different probiotic strains. In addition, the comple-
ment activity, serum IgM level, respiratory burst, phagocytic activity and expression of seven
selected immune-related genes were also evaluated in sea bream HK samples following com-
bined or individual dietary administration with microalgae ( Phaeodactylum tricornutum and
Tetraselmis chuii ) and B. subtilis (Cerezuela et al . 2012a). The dietary applications of B.
subtilis , Tetraselmis chuii and Phaeodactylum tricornutum , singly or in combination, exhibit
up-regulating effects on gilthead sea bream immune parameters, although Phaeodactylum
tricornutum demonstrated the highest immunomodulatory activity. Despite this no protec-
tion was afforded when sea bream were challenged with Photobacterium damselae subsp.