Biology Reference
In-Depth Information
C. divergens
; it was capable of colonizing the larvae (Strom and Ringo,
1993), could inhibit pathogenic
L. anguillarum
(Gildberg and Mikkelsen,
1998), but gives a temporary and marginal protection to the fry.
Lactobacillus acidophilus
(unspecifi ed strain) was used in a diet to test
the protection it confers to the tiger shrimp (
Penaeus monodon
) postlarvae
challenged with a pathogenic strain of
Vibrio harveyi
(Immanuel et al
.
, 2007).
Postlarvae fed with the probiont or with a combination of lactobacilli and
yeast (
Saccharomyces cereviciae
), survived signifi cantly better at the end of
10 d; 94.3 and 82.3% respectively versus 26.5% of untreated postlarvae.
The
V. harveyi
load in the hepatopancreas and muscle tissues was also
signifi cantly reduced by orders of magnitude (Immanuel
et al
.
, 2007).
A strain of
Enterococcus faecium
(MC13) was also tested in
P. monodon
postlarvae challenged with
V. harveyi
and
V. parahaemolyticus
(Swain et
al., 2009). MC13 signifi cantly reduced the mortality of the postlarvae, 84%
survival against 60% when challenged with a strain of
V. harveyi
, however
little protection was conferred against
V. parahaemolyticus
.
The probable mechanisms of action of LAB could be the inhibition of
pathogens (vibrios) by the production of lactic and acetic acids and not
by bacteriocins which cannot access to the plasmatic membrane of Gram
negative bacteria (Vazquez
et al., 2005).
Bacillaceae
Bacillus
sp. spores (strain IP 5832) improved the survival of larvae
signifi cantly when included with rotifers by reducing the density of an
opportunistic bacterial strain (Gatesoupe, 1991). The taxonomic status
of this potential pathogens is not clear as it is referred as
Vibrio
sp. by
Gatesoupe (1991) citing a previous article where it is identifi ed as
Aeromonas
sp. (Gatesoupe, 1990). With the tiger shrimp (
Penaeus monodon
)
larvae, another
Bacillus
spp. (strain S11) was used mixed with the feed as
fresh cells or lyophilized and challenged with
V. harveyi
D331 (Rengpipat
et al., 1998). After 10 d, larvae survival was signifi cantly higher than the
untreated larvae with any of the different feeds prepared with the probiont.
When the larvae were dissected and their microbial loads analyzed, those
larvae that received the probiotic feed,
Bacillus
sp. S11 was the principal
bacteria found at densities of up to 10
8
CFU/g of gut (Rengpipat
et al
.
,
1998). When the experiment was repeated with a different culture system
(recirculation), the probiotic effect measured as survival and growth was
signifi cant only at certain days post challenge (Rengpipat
et al
.
, 2000).
The immune response of probiotic treated larvae was evaluated and a
signifi cant enhancement of percent phagocytosis, phagocytic index, total
hemocytes, and phenoloxidase was observed (Rengpipat
et al
.
, 2000).
They speculate that the mode of action of S11 was competitive exclusion
