PhD Thesis MJProl .pdf - digital-csic Digital CSIC - Consejo Superior ...

New strategies for the control of bacterial infections in marine fish larval rearing 11
Carnevali et al., 2004; Gatesoupe, 1991, 1994; Planas et al., 2004; Plante et al., 2007;
Villamil et al., 2003; Suzer et al., 2008). Commercial yeasts have also been proposed as
probiotics (Tovar-Ramírez et al., 2002).
A better strategy, that avoids the introduction of non-native microorganisms to the
system, is to select probiotic candidates among strains isolated from healthy fish (Meuer
et al., 2006; Olsson et al., 1992; Ottesen and Olafsen, 2000; Westerdahl et al., 1991) or
hatchery facilities (Hjelm et al., 2004a, b; Huys et al., 2001). The efficacy of
autochthonous probiotics is likely to be highest in the host species from which the
bacteria were isolated from (Verschuere et al., 2000).
Generally, selection is based on the antagonistic effect of the potential probiotic
against pathogenic bacteria responsible of high mortalities in larvae, such as Listonella
anguillarum (Olsson et al., 1992; Planas et al., 2006), Vibrio sp (Gatesoupe, 1994;
Vine, 2004a, b) or Aeromonas sp (Ringø and Vadstein, 1998; Vine, 2004a, b), but in
vitro growth and adhesion to mucus, immunostimulation or enhancement of enzymatic
activity have been also used as criteria for probiotic selection (Gatesoupe, 1994;
Picchetti et al., 2009; Suzer et al., 2008; Vine et al., 2004a, b). It is important to notice
that probiotics can be added directly to the seawater or introduced into the system
previously bioencapsulated in live feed (Table 1.1). In some cases the final effect may
depend on the selected way of delivery.
• Synbiotics
A synbiotic is defined as a combination of a probiotic with a prebiotic, usually a
selective substrate, which ensures the growth and the permanence of the associated
probiotic (Ziemer and Gibson, 1998). In aquaculture, the use of synbiotics has been
proposed by Vine et al. (2006) but, at the present moment, only in vitro trials have been
conducted to assay the potential of non-digestible carbohydrates and other prebiotics on
the growth of probiotics (Rurandwa et al., 2009).