Biology Reference
In-Depth Information
Lactobacillus plantarum
) have been shown to protect 9-d-old larvae of turbot
(
Scophthalmus maximus
) when inoculated at high densities (10
7
CFU/mL)
against a pathogenic
Vibrio splendidus
(Vibrio P), with survival differences
of as much as 79% (Gatesoupe, 1994).
C. divergens
was also tested against a
pathogenic
V. pelagius
in turbot larvae but the results were inconclusive as
larvae mortalities were, at most, only delayed (Ringo, 1999).
Rainbow trout fry (1-2 g) and fi ngerlings were used to evaluate the
probiotic strain K1 of
Carnobacterium
sp., a strain capable of inhibiting
several bacterial pathogens (Jöborn
et al
.
, 1997; Robertson
et al
.
, 2000). This
strain could still be isolated from the intestines of fi sh fry after 10 d after
the end of the probiotic feeding period. In this study, only juveniles (20 g)
were challenged with two pathogens (
Aeromonas salmonicida
and
Yersinia
ruckeri
) with signifi cant survival enhancements in those organisms fed
with the probiont. If this probiont can also protect larvae or fry is still a
matter of speculation (Gildberg and Mikkelsen, 1998).
Although no infection challenges have been carried out with Gilt-head
sea bream (
Sparus aurata
) larvae to test potential probiotics, experiments
have been done to evaluate the stress response and stimulation of the gut
immune system of larvae. Larvae exposed to
Lactobacillus fructivorans
and
L. plantarum
colonized the gut differently after 35, 66, and 90 d post hatching
(Carnevali
et al
.
, 2004) and affected the bacterial genera decreasing potential
pathogenic groups such as Enterobacteriaceae and
Staphylococcus
(Rollo
et al., 2006). Stress response of the larvae was signifi cantly infl uenced by
the administration of the potential probionts; larvae exposed to pH stress
survived better as compared to untreated controls (Rollo
et al., 2006). The
gut immune system of
S. aurata
and
Dicentrarchus labrax
was stimulated by
the addition of
L. delbrueckii
subsp.
delbrueckii
and
L. fructivorans
combined
with
L. plantarum
orally via live carriers (
Artemia
sp. nauplii and rotifers)
(Abelli et al. 2009).
Atlantic cod (
Gadus morhua
) fry have also been challenged with a
pathogenic strain of
L. anguillarum
(strain LFI 1243) by supplementing
their feed with an unspecifi ed strain of
Carnobacterium divergens
(Gildberg
and Mikkelsen, 1998; Gildberg et al., 1997). Signifi cant reductions in
mortalities in treated fry were observed 12 d after infection but cumulative
mortalities level out after 4 wk. The probiotic bacterium was supplied
to the fry at a density of 2 x 10
9
CFU/g feed. In this study, fry were also
offered a diet with intact muscle protein (no bacteria added), and those
fi sh had the lowest cumulative mortalities (Gildberg
et al
.
, 1997). Mixed
cultures
in vitro
of both bacterial strains did not show an obvious inhibition
of the pathogen (Gildberg
et al
.
, 1997). Previously, this strain (identifi ed as
L. plantarum
) was fed to 5 d old larvae and after 4 d the bacterial fl ora
was dominated by it as compared to the controls (Strom and Ringo, 1993).
These results make it diffi cult to evaluate the true action of the probiont
