Probiotic Applications in Crustaceans - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 297

transcription) and the antioxidant enzyme superoxide dismutase activity (SOD) of the white
shrimp. They also showed that this effect was associated with increased pathogen clearance
efficiency and resistance to a pathogenic V. alginolyticus strain, suggesting that the probiotic
was able to induce immune modulation and a subsequent increase in resistance to bacterial
infection. Additional studies suggested a similar effect of LAB on the immune and antiox-
idant defences of shrimp resulting in higher resistance to bacterial infections (Castex et al.
2009; 2010; Viera et al. 2007; 2008).
Finally, the effect of LAB on some nutritional aspects in different marine shrimp species
has also received some attention (Uma et al. 1999; Venkat et al. 2004; Castex 2009). Never-
theless, future studies should highlight the potential and the precise mode of action of LAB as
probiotics for crustaceans.
11.2.3 Other Gram-positive bacteria
A number of other Gram-positive bacteria have also received attention as potential probiotics
for crustacean culture. Li etal. (2006) compared an Arthrobacternicotianae strain to an antibi-
otic treatment (Chloramphenicol) to protect Chinese shrimp post larvae from pathogenic Vibrio
spp. To the authors' knowledge this study is the first evaluation of Arthrobacter sp. as a possi-
ble probiotic bacterium in aquaculture. While bath infection with a combination of pathogenic
Vibrio spp. ( V. parahaemolyticus , Vibrio anguillarum and Vibrio nereis ), isolated from sick
'red-leg' shrimps, led to 43% mortality of the post larvae at the end of the 14 day experimental
period, the shrimps receiving the probiotic bath treatment showed an 82.6% survival rate which
was a level of protection similar to that obtained with the antibiotic treatment. The authors iso-
lated the strain from Fenneropenaeuschiniensis culture water samples but did not clearly report
why this particular microorganism was selected. Nevertheless, they evoked several interesting
properties of microorganisms from the genus Arthrobacter such as the production of antimi-
crobial compounds, the ability to nitrify and to use a wide range of organic substances, or
again their ability to produce amino acids, vitamins and polysaccharides. Recently, Pai et al.
(2010) also concluded that an Arthrobacter sp. strain (MCCB 104) functioned as probiotic in
P. monodon larvae but suggested immunostimulatory and digestive enzyme-supporting modes
of action in the absence of in vitro antagonistic effects toward Vibrio spp.
A recent study from Antony et al. (2011) showed the effect of three probiotic preparations
containing a Bacillus strain and a Micrococcus strain alone, or in combination, on sub-adult
black tiger shrimps. Even though Micrococcus sp. has been rarely identified as a normal inhab-
itant of the GI tract of penaeid shrimps, these authors focused their investigation on the putative
effect of one strain on the immunity and the subsequent ability of the shrimp to resist a white
spot syndrome virus (WSSV) challenge. The study revealed that the probiont administered
individually or in combination with a Bacillus sp. was found to modulate the level of expression
of antimicrobial peptide genes in P. monodon , leading to higher survival rate of the shrimps
following a WSSV infection. However, the Micrococcus strain was found to be less effective
than the Bacillus strain when tested alone.
11.2.4 Gram-negative bacteria
Gram-negative bacteria, especially Gammaproteobacteria, are also being used extensively as
probiotics for crustaceans. Indeed members of the Gammaproteobacteria phylum are
amongst the most commonly reported, and often most abundant, species present in the