Agriculture Reference
In-Depth Information
8.3.1
Carnobacterium
spp.
In most of the early investigations on the intestinal LAB in fish,
Carnobacterium
and
Lactobacillus
were not easily distinguished (Ringø and Gatesoupe 1998). Today, however,
based on new information and technological advances, it is easy to distinguish
Carnobac-
terium
from
Lactobacillus
by the presence of meso-diaminopimelic acid in the cell wall, the
isomers of lactic acid produced, production of citrulline from arginine, growth on acetate and
CTAS agar plates and 16S rRNA sequencing (Ringø and Gatesoupe 1998).
During the last 15 years, several strains of
Carnobacterium
have shown potential for
successful probiotic applications with fish species. These include
Carnobacterium mal-
taromaticum
(Kim and Austin 2006) (
C
.
maltaromaticum
was previously
Carnobacterium
piscicola
, but this was reclassified in 2003: Mora
et al
. 2003),
Carnobacterium divergens
(Gildberg
et al
. 1995; 1997; Gildberg and Mikkelsen 1998; Ringø 1999; Kim and Austin
2006; Gopalakannan and Arul 2011),
Carnobacterium inhibens
(previously
Carnobacterium
strain K1) (Jöborn
etal
. 1997; Robertson
etal
. 2000; Irianto and Austin 2002) and unidentified
Carnobacterium
spp. (Irianto and Austin 2002). Furthermore, some studies have suggested
that carnobacteria have the potential to colonize the digestive tract of cold water fish such as
salmonids (Gildberg
et al
. 1995; Jöborn
et al
. 1997; Robertson
et al
. 2000; Irianto and Austin
2002; Kim and Austin 2006) and Atlantic cod
Gadus morhua
(Gildberg
et al
. 1997; Gildberg
and Mikkelsen 1998) (Table 8.2).
The early study by Jöborn
et al
. (1997) demonstrated that
C. inhibens
(originally isolated
from the gut of Atlantic salmon and designated as strain K1, later identified as
C. inhibens
:
Jöborn
et al
. 1999) grew well in rainbow trout intestinal mucus
in vitro
and showed in
in vivo
experiments that
C.inhibens
was able to survive gastric passage and persist within the digestive
tract of rainbow trout fingerlings.
C. inhibens
was administered via the feed at levels of 4 ×
10
7
CFU g
-1
and faecal
Carnobacterium
levels were reported at 10
6
-10
7
CFU g
-1
during the
supplemented feeding phase. Despite this, and the observed
in vitro
adhesion to and growth
within intestinal mucus,
C. inhibens
cells were not detected within the intestinal mucus, and
so the authors suggested that
invivoC.inhibens
populates the lumen rather than the mucosa of
the intestinal tract. Following this, Robertson
et al
. (2000) fed rainbow trout fry, rainbow trout
fingerlings and Atlantic salmon fingerlings
C. inhibens
,at5× 10
7
cells g
-1
for up to 28 days,
and reported that
C.inhibens
remained viable within the digestive tract of the salmonids during
feeding and that a clear time-dependent relationship was evident. For example, in rainbow trout
fingerlings,
Carnobacterium
reached maximum levels (7.4 × 10
6
g
-1
intestine) after 28 days
of probiotic feeding. Similar results were reported by Irianto and Austin (2002) where high
levels of carnobacteria were detected in fish fed
Carnobacterium inhibens
and an unidentified
Carnobacterium
spp. (isolate BA211) for 7 days. The recovery of
C. inhibens
displayed a
clear relationship with the duration of feeding; intestinal levels increased fourfold over the 7
day period from 5.5 × 10
6
to 2.1 × 10
7
CFU g
-1
after 1 and 7 days feeding, respectively. This
time-dependent response was not observed for
Carnobacterium
spp. isolate BA211 which
remained present at high levels (ca. 5 × 10
6
CFU g
-1
) within the intestine with no evident
relationship with feeding duration.
Despite the reported inability of
C. inhibens
to populate the intestinal mucosa of trout
(Jöborn
et al
. 1997) it has been reported that
C. divergens
and
C. maltaromaticum
(origi-
nally isolated from rainbow trout) displayed exceptional qualities for the successful population
of the rainbow trout intestine (Kim and Austin 2006). Dietary application for 14 days at
10
7
CFU g
-1
led to probiont levels of
>
>
90% and
99% of the total culturable populations
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