Indigenous Lactic Acid Bacteria in Fish and Crustaceans - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 150

6.14 SILURIFORMES
A number of studies have reported LAB to be present in the GI tract of catfishes but few
investigations have focused on determining the levels or their importance to the host. Perhaps
the most informative study is that of Hagi et al . (2004) which investigated the composition of
intestinal LAB in channel catfish ( Ictalurus punctatus ) during the summer and winter. LAB
levels accounted for ca. 10% of the culturable populations and were composed of Lc. lactis
(100% of 20 isolates) in the summer and Lc. raffinolactis (100% of 20 isolates) in winter. In
other studies Lb. casei subsp. paracasei and Lb. brevis have been identified from the gut of
African catfish ( Clarias gariepinus ) (Bucio et al . 2006), Lactobacillus spp. from wels catfish
( Silurus glanis ) (Bucio et al . 2006) and Lc . lactis from the Amur catfish ( Silurus asotus L.)
(Sugita et al . 2007). In the study of Sugita et al . (2007), 49 strains of Lc . lactis were isolated
from the intestinal content of the Amur catfish. These LAB were tested for their antibacterial
abilities to inhibit in vitro growth of five species of Aeromonas . In a later study (Sugita et al .
2009) the authors subsequently reported that Lc . lactis strain C7 showed higher antibacterial
potential than the strains tested in the 2007.
Le Nguyen et al . (2008) isolated Lb . plantarum from the intestinal contents of the
Pangasius ( Pangasius hypothalamus ). In a study evaluating the microbial diversity of mucus
and intestinal contents of yellow catfish ( Pelteobagrus fulvidraco ), Wu et al . (2010) reported
two LAB, Enterococcus saccharominimus and Lc . garvieae , from a clone library constructed
from the intestinal contents, but no LAB were detected in the mucus clone library and no
cultivable LAB were isolated from intestinal contents or mucus. In a more recent study, Wu
et al . (2012b) characterized the bacterial community in the stomach of yellow catfish. Of
the 45 phylotypes reported from 65 positive clones from the gastric contents, two clones
showed 94.8% similarity to Lactobacillus aviaries . In contrast to this result, no lactobacilli
were reported from the cultured bacteria isolated from the stomach contents or from the clone
library from stomach mucus.
6.15 CICHLIDAE
A number of studies have identified LAB from the GI tract of tilapia. Streptococcus spp.
have been identified as components of the culturable aerobic intestinal microbiota of tilapia
in a number of studies (Al-Harbi and Uddin 2003; 2004; 2005). Al-Harbi and Uddin (2003)
reported Streptococcus spp. levels of 0.58% of the total culturable community in the intestine
of hybrid tilapia ( Oreochromis niloticus × Oreochromis aureus ) but in their later studies it was
apparent that seasonality impacted these levels. For example, Streptococcus spp. were absent
in the intestine of hybrid tilapia during the summer but accounted for ca. 5% of the culturable
population in the autumn and 3% in the winter (Al-Harbi and Uddin 2004). In a study evaluat-
ing the effect of florfenicol and Saccharomyces cerevisiae on the gut bacterial community of
hybrid tilapia, Lc . lactis was detected in the intestine of all groups investigated, but the abun-
dance was highest in the group fed sequential florfenicol (8 weeks) and S . cerevisiae (8 weeks)
and lowest when the fish were fed S . cerevisiae (He et al . 2011b).
In Nile tilapia ( Oreochromis niloticus ) reared in brackish water Streptococcus spp.
accounted for 12% of the culturable intestinal community (Al-Harbi and Uddin 2005). In a
later study of Nile tilapia, Jatoba et al . (2008) isolated Lb . plantarum and Lb . brevis from