Agriculture Reference
In-Depth Information
6.21 SUMMARY
To our knowledge the first article dealing with LAB in fish was published by Kraus in 1961
and, until the end of the 1980s and the beginning of the 1990s, interest in LAB in fish and shell-
fish was generally low. However, during the last decade, our knowledge of the importance of
gut microbes on host development and functions in terrestrial vertebrates and more recently in
fish has grown. Concomitantly with the moratorium on the use of antibiotic growth promoters
in feeds, interest in fish gut microbes and methods to fortify these communities has increased
exponentially. Based on the information presented in this chapter a general conclusion can be
drawn: intestinal LAB are not generally the dominant gut bacteria in fish and shellfish. How-
ever, their relevance and importance to the host likely outweigh their proportional abundance.
In this chapter we have presented an overview of LAB as members of the intestinal micro-
biota of fish and shellfish species. LAB isolated from the GI tract of fish and shellfish species
belong to the following families and genera:
Aerococcaceae
,
Aerococcus
;
Carnobactericeae
,
Carnobacterium
;
Enterococcaceae
,
Enterococcus
and
Vagococcus
;
Lactobacillaceae
,
Lacto-
bacillus
and
Pediococcus
;
Leuconostocaecae
,
Leuconostoc
and
Weissella
; and
Streptococ-
caceae
,
Lactococcus
and
Streptococcus
. Extremely low levels of bifidobacteria have been
reported from a limited number of individuals of a small number of fish species. To our knowl-
edge,
Tetrageonococcus
within the family
Enterococcaceae
, and
Oenococcus
within the family
Leuconostocaecae
, have not been reported.
Since conventional characterizations of microorganisms have depended on cultivation
based techniques, our understanding of the intestinal microbiota composition has been
restricted to those that can be cultured. It is acceptable and informative to continue to isolate
and identify LAB in the GI tract of fish and shellfish in order to elucidate their drug resistance,
enzyme production and ability to inhibit
in vitro
growth of potential fish pathogens. However,
as the intestinal microbiota of fish and crustacea are complicated ecosystems modulated by
internal and external factors, next-generation sequencing, metagenetic approaches and eluci-
dation of LAB activity and functionality
in situ
are topics that merit extensive investigations.
These approaches will aid in the understanding of commensal and symbiotic LAB-host
interactions in the GI tract, aid the identification of probiotic candidates, and extend our
knowledge on the pathogenic LAB. Indeed indigenous pathogenic and opportunistic LAB
such as
Streptococcus
,
Enterococcus
,
Lactobacillus
,
Carnobacterium
and
Lactococcus
have
been reported in the GI tract of aquatic animals. In freshwater fish, Austin and Robertson
(1993) reported that
Str. milleri
caused disease to carp. Later, Perera
et al
. (1994) suggested
that
Str. iniae
was associated with mortality of hybrid tilapia, while Al-Harbi (1994) reported
that
Streptococcus
sp. caused disease in hybrid tilapia in Saudi Arabia. Eldar
et al
. (1994)
isolated and identified two new streptococcal species (
Streptococcus shiloi
and
Streptococcus
dificile
) which caused meningoencephalitis in tilapia. Readers with special interest in
pathogenic LAB are referred to Ringø and Gatesoupe (1998), Ringø (2004), Gatesoupe
(2008), Loch
et al
. (2008; 2011; 2012), Austin and Austin (2012), Lauzon and Ringø (2012)
and Leisner
et al
. (2012).
REFERENCES
Abelli, L., Randelli, E., Carnevali, O. and Picchietti, S. (2009) Stimulation of gut immune system by early
administration of probiotic strains in
Dicentrarchus labrax
and
Sparus aurata
.
Trends in Comparative
Endocrinology and Neurobiology: Annals of the New York Academy of Sciences
1163
, 340-342.
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