Probiotic Applications in Cold Water Fish Species - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 232

subtilis JB-1 conferred protection against A. salmonicida , Lc. garvieae , Streptococcus iniae ,
V .( L .) anguillarum , V. ordalii and Y. ruckeri in rainbow trout. The mode of action reflected
nutrition, production of inhibitory substances and stimulation of the innate immune responses.
The modulation of rainbow trout immune responses with probiotic bacteria has been the
subject of much attention and this property has been recognized as a key mode of action pro-
tecting fish against bacterial infections (Sharifuzzaman and Austin 2009). Sakai et al . (1995)
demonstrated that oral administration of Clostridium butyricum enhanced rainbow trout resis-
tance to vibriosis by increasing the phagocytic activity of leukocytes. The supplementation of
Aeromonas hydrophila A3-51, Vibrio fluvialis A3-47S, Carnobacterium sp. BA211 or Micro-
coccus luteus A1-6 was able to increase serum lysozyme activity in rainbow trout (Irianto and
Austin 2002). Moreover, higher serum lysozyme and total protein levels were recorded after
rainbow trout were fed Kocuria sp. SM1 and then challenged with V.anguillarum (Sharifuzza-
man and Austin 2009). Some LAB strains that are generally used as human probiotics, such as
Lactobacillus rhamnosus , have been considered for use in rainbow trout (Nikoskelainen et al .
2001a; Panigrahi et al . 2005) and have stimulated respiratory burst activity (Nikoskelainen
et al . 2003) and superoxide anion production of rainbow trout head kidney (HK) leukocytes
(Panigrahi et al . 2005). The production of pro-inflammatory and anti-inflammatory cytokines
is another immune mechanism that probiotics can modulate. In fact, administration of Entero-
coccus faecium , Lb. rhamnosus or B. subtilis was able to up-regulate interleukin-1β1(IL-1β1)
and transforming growth factor β (TGF-β) in rainbow trout (Panigrahi et al . 2007). Similarly,
Pérez-Sánchez et al . (2011) demonstrated that administration of Lactobacillus plantarum ,iso-
lated from the intestinal mucosa of rainbow trout, was able to up-regulate pro-inflammatory
cytokine gene expression in the HK and intestine. Dietary Pediococcus acidilactici treatment
may also potentiate the immune responsiveness of the rainbow trout intestine. Abid et al .
(2012) observed an up-regulation of the gene expression of the pro-inflammatory cytokines
IL-1β and IL-8 and down-regulation of the anti-inflammatory IL-10, compared to control fed
fish. In addition, the mRNA levels for the mucosal antibody IgT was also elevated in probiotic
fed fish.
Probiotics have also been suggested to have a beneficial effect in the digestive processes by
promoting nutrient uptake or providing nutrients and vitamins (Ringø and Gatesoupe 1998),
and also improving digestibility and weight gain. For instance, enhanced growth was observed
in rainbow trout after the supplementation of Saccharomyces cerevisiae (Tukmechi et al.
2011). Similar results have been reported using the same yeast species by Sheikhzadeh et al .
(2012), suggesting that yeast supplementation may promote lysozyme, protease, alkaline
phosphatase and esterase activities in rainbow trout. Dietary provision of S . cerevisiae var.
boulardii has also been reported to enhance rainbow trout intestinal enzymatic activities
(Waché et al . 2006). Although information on the effect of bacterial probiotics on intestinal
enzymatic function in trout is not presently available, limited studies have reported improved
digestive morphology (Merrifield et al . 2010d), feed utilization (Bagheri et al . 2008) and
growth performance (Bagheri et al . 2008). The majority of bacterial probiotic studies in trout
which have assessed growth performance, as listed in Table 9.1, report no benefits in growth
performance relative to control fed fish.
The present studies indicate that probiotic treatments offer a promising alternative to the
use of chemotherapeutic agents in the trout industry, but further studies are required to elu-
cidate the exact mechanisms of action involved, as well as the limitations in the use of these
microorganisms as a prophylactic or therapeutic measure in these production systems.