705
Probiotics/Biological Control
There has been a great increase in the number of publications about probiotics over
the last two decades. There is much evidence that members of the natural aquatic
microfl ora, including components of the fi sh intestinal microfl ora (Fjellheim et al.
2007 ; Pérez-Sánchez et al. 2011 ), are effective at inhibiting fi sh pathogens, by competitive exclusion (e.g. Laloo et al. 2010 ) which may involve the production of
antibiotics or low molecular weight inhibitors. Dopazo et al. ( 1988 ) discovered the
presence in the marine environment of antibiotic-producing bacteria, which inhibited a range of bacterial fi sh pathogens, including Aer. hydrophila . These inhibitors
produced low molecular weight (<10 kDa) anionic, thermolabile antibiotics.
Subsequently, Chowdhury and Wakabayashi ( 1989 ); Austin and Billaud ( 1990 ) and
Westerdahl et al. ( 1991 ) reported the presence of microbial inhibitors of Fla. columnare, Ser. liquefaciens and V. anguillarum. Smith and Davey ( 1993 ) identifi ed a
fl uorescent pseudomonad which antagonised Aer. salmonicida. Apart from the lactic acid bacteria (e.g. Pérez-Sánchez et al. 2011 ), that are mostly linked with probiotic activity in terrestrial animals, aquaculture has utilised a wide range of
Gram-positive and Gram-negative bacteria, yeast, microalgae and even bacteriophages. The use of Gram-negative bacteria from genera associated with fi sh disease, e.g. Aeromonas and Vibrio, is of concern because of the perceived risk of the
introduction of virulence genes such as by horizontal gene transfer although this has
never occurred – yet! “Good” bacteria have been described for the control of numerous diseases, and there is a tendency that the probiotic works faster than an oral
vaccine (see Irianto and Austin 2002 ). The assumption that probiotics must be live
preparations was dashed when it was demonstrated that formalised suspensions of
cells were effective at controlling atypical Aer. salmonicida infection in goldfi sh
(Irianto et al. 2003 ) and furunculosis in rainbow trout (Irianto and Austin 2003 ),
when applied as feed additives. Furthermore, subcellular components, i.e. OMPs
and ECPs, of probiotics were immuno-reactive with V. harveyi antiserum (Arijo
et al. 2008 ) and were immunostimulatory and protected against challenge with Aer.
hydrophila in rohu (Giri et al. 2015a , b ). Along a similar theme, i.p. or i.p. injection
of cell wall proteins, OMPs, LPS and whole cell proteins of two probiotics, A.
sobria GC2 and Bacillus subtilis JB-1 protected rainbow trout against challenge
with Y. ruckeri (Abbass et al. 2009 ). There is evidence that feeding probiotics
enhances the resistance to disease when stocking density is high. Thus, TapiaPaniagua et al. ( 2014 ) described the use of She. putrefaciens Pdp11 in increasing the
stress tolerance of sole ( Solea senegalensis ) when farmed under high stocking levels. The fi sh which received Pdp11 better survived a natural outbreak of disease
caused by Vibrio spp. and modulated the intestinal microfl ora, which was correlated
with a high number of goblet cells (Tapia-Paniagua et al. 2014 ).
Apart from competitive exclusion, probiotics work by stimulation of the innate
immune response (Irianto and Austin 2003 ; Kim and Austin 2006 ) in which case
they could be considered as heterologous oral vaccines, and interference with adhesion to intestinal mucosal surfaces (Chabrillón et al. 2005 ). The benefi cial effect of
probiotics may be further enhanced by the use of prebiotic carbohydrates, notably
Farmed Fish
Probiotics/Biological Control
There has been a great increase in the number of publications about probiotics over
the last two decades. There is much evidence that members of the natural aquatic
microfl ora, including components of the fi sh intestinal microfl ora (Fjellheim et al.
2007 ; Pérez-Sánchez et al. 2011 ), are effective at inhibiting fi sh pathogens, by competitive exclusion (e.g. Laloo et al. 2010 ) which may involve the production of
antibiotics or low molecular weight inhibitors. Dopazo et al. ( 1988 ) discovered the
presence in the marine environment of antibiotic-producing bacteria, which inhibited a range of bacterial fi sh pathogens, including Aer. hydrophila . These inhibitors
produced low molecular weight (<10 kDa) anionic, thermolabile antibiotics.
Subsequently, Chowdhury and Wakabayashi ( 1989 ); Austin and Billaud ( 1990 ) and
Westerdahl et al. ( 1991 ) reported the presence of microbial inhibitors of Fla. columnare, Ser. liquefaciens and V. anguillarum. Smith and Davey ( 1993 ) identifi ed a
fl uorescent pseudomonad which antagonised Aer. salmonicida. Apart from the lactic acid bacteria (e.g. Pérez-Sánchez et al. 2011 ), that are mostly linked with probiotic activity in terrestrial animals, aquaculture has utilised a wide range of
Gram-positive and Gram-negative bacteria, yeast, microalgae and even bacteriophages. The use of Gram-negative bacteria from genera associated with fi sh disease, e.g. Aeromonas and Vibrio, is of concern because of the perceived risk of the
introduction of virulence genes such as by horizontal gene transfer although this has
never occurred – yet! “Good” bacteria have been described for the control of numerous diseases, and there is a tendency that the probiotic works faster than an oral
vaccine (see Irianto and Austin 2002 ). The assumption that probiotics must be live
preparations was dashed when it was demonstrated that formalised suspensions of
cells were effective at controlling atypical Aer. salmonicida infection in goldfi sh
(Irianto et al. 2003 ) and furunculosis in rainbow trout (Irianto and Austin 2003 ),
when applied as feed additives. Furthermore, subcellular components, i.e. OMPs
and ECPs, of probiotics were immuno-reactive with V. harveyi antiserum (Arijo
et al. 2008 ) and were immunostimulatory and protected against challenge with Aer.
hydrophila in rohu (Giri et al. 2015a , b ). Along a similar theme, i.p. or i.p. injection
of cell wall proteins, OMPs, LPS and whole cell proteins of two probiotics, A.
sobria GC2 and Bacillus subtilis JB-1 protected rainbow trout against challenge
with Y. ruckeri (Abbass et al. 2009 ). There is evidence that feeding probiotics
enhances the resistance to disease when stocking density is high. Thus, TapiaPaniagua et al. ( 2014 ) described the use of She. putrefaciens Pdp11 in increasing the
stress tolerance of sole ( Solea senegalensis ) when farmed under high stocking levels. The fi sh which received Pdp11 better survived a natural outbreak of disease
caused by Vibrio spp. and modulated the intestinal microfl ora, which was correlated
with a high number of goblet cells (Tapia-Paniagua et al. 2014 ).
Apart from competitive exclusion, probiotics work by stimulation of the innate
immune response (Irianto and Austin 2003 ; Kim and Austin 2006 ) in which case
they could be considered as heterologous oral vaccines, and interference with adhesion to intestinal mucosal surfaces (Chabrillón et al. 2005 ). The benefi cial effect of
probiotics may be further enhanced by the use of prebiotic carbohydrates, notably
Farmed Fish