Agriculture Reference
In-Depth Information
In a study by Tapia-Paniagua
etal
. (2011) the authors evaluated modulation of the intestinal
allochthonous microbiota of gilthead sea bream (∼80 g) by administration of
Debaryomyces
hansenii
in combination with inulin. Experimental fish were fed either a commercial diet
(control diet) or adiet supplemented with
D. hansenii
strain L2 (10
6
CFU g
−1
) plus 3% inulin
(experimental diet II) for 4 weeks. After 2 and 4 weeks of feeding, samples of the whole intes-
tine were aseptically removed for allochthonous microbiota analysis using PCR-DGGE and
sequence analysis. Additionally, the expression of 12 selected genes related to the immune
response (IgM, MHCIα,MHCIIα,C3,IL-1β, TLR9A, TNFα, CSF-1R, NCCRP-1, Hep, TCRβ
and CD8) from the skin, intestine, liver and HK tissue were analysed by real-time PCR. Sam-
ples of blood and HK were obtained for the determination of humoral and cellular immune
parameters. The results showed that fish fed the experimental diet had lower intestinal micro-
bial species richness and greater similarity indices compared with fish fed the control diet
for 4 weeks. It is of interest to note that
Pseudomonas
spp. dominated the intestinal micro-
biota in both experimental groups. Peroxidase activity was the only haematological param-
eter that was significantly increased in fish fed the synbiotic diet. RT-PCR revealed that a
number of the selected immune-related genes were generally up-regulated in the skin and
intestine after 2 weeks of feeding the synbiotic diet. The maximum transcript levels were
reported in the intestine for the major histocompatibility complex (MHC) genes MHCI and
MHCII, which were significantly up-regulated. After 4 weeks of feeding, relatively lower
gene transcript levels were recorded in the skin and intestine, but higher levels of comple-
ment 3 (C3), the pro-inflammatory cytokine TNFα and colony stimulating factor 1 receptor
(CSF-1R), a receptor for a cytokine which controls macrophage production, differentiation and
function, were observed in the intestine. In addition, at week 4 a greater effect was observed
in the HK than at week 2. This was especially prominent in the up-regulation of C3, the
pro-inflammatory cytokine IL-1β, CSF-1R and non-specific cytotoxic cell receptor protein
1 (NCCRP-1, a surface protein which functions in target cell recognition and cytotoxicity).
Similar localized intestinal effects of synbiotics have been observed in Atlantic salmon fed
Pediococcus acidilactici
(10
6
CFU g
−1
) and scFOS (7g kg
−1
) for 63 days (Abid
et al
. 2013).
The synbiotic application modulated the allochthonous gut microbiota, including the presence
of
Ped. acidilactici
, and subsequently up-regulated the gene expression of pro-inflammatory
cytokines (IL1β,TNFα and IL8) and antiviral proteins (toll-like receptor 3 (TLR3) and Myx-
ovirus resistance protein (MX-1)). Both of these studies indicate elevated immune respon-
siveness and the potential for improved disease resistance. Indeed, Lin
et al
. (2012) observed
elevated peripheral total leukocyte counts, respiratory burst, lysozyme and superoxide activ-
ities, which afforded increased protection against
A
.
veronii
infection in koi fed a synbiotic
application of
Bacillus coagulans
and COS. In addition, the inclusion of the synbiotic signifi-
cantly improved SGR and FCR.
In three recent studies with gilthead sea bream, Cerezuela and colleagues evaluated the
effect of
Bacillus subtilis
and inulin on immune-related gene expression and disease resis-
tance against
P
.
damselae
subsp.
piscicida
(Cerezuela
et al
. 2012), gut microbiota and gut
histology (Cerezuela
et al
. 2013a), and expression of different genes in the anterior intestine
(Cerezuela
et al
. 2013b). Synbiotic administration significantly increased complement activ-
ity following 4 weeks of feeding, but not after 2 weeks of feeding. Respiratory burst activity
was not affected after 2 and 4 weeks feeding. Serum IgM level was significantly higher after
2 weeks of feeding but not after 4 weeks. The expression of immune-related genes in the HK
of fish fed synbiotic for 2 weeks displayed no significant effect, although the expressions of
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