Indigenous Lactic Acid Bacteria in Fish and Crustaceans - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 153

recent study, Tanaka et al . (2012) evaluated the bacterial diversity of the intestinal tracts of six
Japanese coastal fish by constructing clone libraries, but the only LAB reported were isolates
showing high similarity to Streptococcus sanguinis isolated from Girella punctata , and S . san-
guinis was a major bacterium in the intestinal tract of the fish species (Haruo Sugita, personal
communication 2012).
6.20 SHELLFISH
The use of indigenous bacterial species is paramount in probiotic applications from both leg-
islative and ecological perspectives. It is therefore essential to consider the native bacterial
species present in a given host species to aid decisions on suitable probiotic species. However,
unlike finfish, there is a paucity of studies which have investigated the indigenous gut bacteria
in shellfish species.
Despite this, LAB have been reported to be indigenous to shellfish species including shrimp
and prawns (Cai et al . 1999; Lalitha and Surendran 2004; Kennedy et al . 2006; Vieira et al .
2007; 2008; Zhou et al . 2007; Kosin and Rakshit 2010; Vieira et al . 2010; Leyva-Madrigal
et al . 2011; Liu et al . 2011; Kongnum and Hongpattarakere 2012), swimming crab ( Call-
inectes and Portunus spp.) (Uaboi-Egbenni et al . 2010; Talpur et al . 2012), mud crab ( Scylla
paramamosain )(Li et al . 2012), lobster (Daniels et al . 2010; 2013; Meziti et al . 2010), scallop
(Campa-Cordova et al . 2011) and abalone (Sarkono et al . 2010) (Table 6.3). In an early study
by Cai et al . (1999) the presence of several LAB belonging to the Lactococcus , Enterococcus
and Pediococcus genera were reported in the intestine of the giant freshwater shrimp ( Macro-
brachium rosenbergii ). Three specific isolates were identified to species level as Lc. garvieae ,
P. acidilactici and E. faecium using 16S rRNA gene sequencing. Later, Lalitha and Surendran
(2004) reported that Enterococcus spp. accounted for 8.3% of the identified gut bacteria in
adult M. rosenbergii . Kennedy et al . (2006) investigated the microbiota associated with M.
rosenbergii larvae, and among the bacteria isolated the authors identified a small proportion
of lactobacilli, accounting for approximately 4.5% of the culturable microbiota. Lactobacillus
were only present at the early life stages however, being absent in larval stages past day 4
of development, and this absence continued up to stage six of post larval development. More
recently, Vieira et al . (2007) isolated two LAB from the digestive tract of juvenile Litope-
naeus vannamei using culture-dependent agar plating techniques; one of these strains was
later identified as Lb. plantarum by 16S rRNA gene sequencing (Vieira et al . 2008). It might
be suggested from additional experiments that this LAB strain is transient in nature within the
digestive tract of L. vannamei , as probiotic supplementation trials with Lb. plantarum showed
that six days after changing from the probiotic enriched diet to a control diet, total LAB counts
in the gut were low and not significantly different from control shrimps (Vieira et al . 2008).
Moreover, this and a later study by Vieira et al . (2010) identified detectable levels of LAB,
using culture-dependent methods, in the digestive tract of L . vannamei . Kosin and Rakshit
(2010) identified autochthonous LAB from L. vannamei using selective media (for probiotic
and thermo-tolerant bacteria). These LAB were identified as Lb . plantarum and Leu . mesen-
teroides subsp. mesenteroides / dextranicum by API 50 CHB and API 50 CHL. Leyva-Madrigal
et al . (2011) isolated P . pentosaceus and Streptococcus haemolyticus from the intestine of
L. vannamei . The LAB were tested for extracellular enzymatic activities and inhibitory activ-
ities and were used as probiotics to reduce WSSV and IHHNV in naturally infected whiteleg