Agriculture Reference
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shrimp. Based on their results, the authors concluded that the isolates of P . pentosaceus and
Str.haemolyticus were good candidates to be used as feed additives in whiteleg shrimp culture.
Liu et al . (2011) identified E. faecalis from the microbiota of the Chinese shrimp ( Fennerope-
naeus chinensis ) by using DGGE. However, construction of a clone library (72 clones were
sequenced) did not reveal members of the Enterococcus genera which indicates that it was
not amongst the most abundant bacteria present. More recently a study of the GI tract of wild
and cultured yellow shrimp ( Metapenaeus brevicornis ), banana shrimp ( Penaeus merguiensis )
and white shrimp ( L.vannamei ) isolated 202 LAB strains, via culture-dependent techniques, of
which 78-79% were coccoid LAB, potentially Streptococcus , Lactococcus and/or Enterococ-
cus (Kongnum and Hongpattarakere 2012). In an earlier study analysing the GI tract of L. van-
namei , low population levels of presumptive Lactobacillus spp. and Str . faecalis were present
in the intestine of control and short-chain fructooligosaccharides (scFOS) fed shrimp (Zhou
etal . 2007). Studies assessing the GI tract of post-larval European lobster Homarusgammarus
identified the presence of Weissella spp. using PCR-DGGE (Daniels et al . 2010; 2013).
Recent studies have isolated LAB in two species of wild swimming crab: Streptococcus
agalactiae has been identified in the GI tract of swimming crab Callinectes sp. (Uaboi-Egbenni
et al . 2010) and Lb. plantarum , Lb. salivarius , Lb. rhamnosus , W. confusa and W. cibaria
have been identified in the GI tract of blue swimming crab ( Portunus pelagicus ) (Talpur et al .
2012). A recent study of mud crabs also identified intestinal LAB, namely Weissella fabaria
and Streptococcus mutans (Li et al. 2012). Talpur et al . (2012) tested the Portunus pelagi-
cus derived isolates for antibacterial effects against V . harveyi , Vibrio parahaemolyticus and
Photobacterium piscicida and the general finding was that the lactobacilli possessed the high-
est antibacterial activity. Nava-Hernández (2008) isolated LAB strain NS61 from the giant
lion's paw scallop ( Nodipecten subnodosu s) which was later tested as a probiotic for the oys-
ter Crassostrea corteziensis (Campa-Cordova et al . 2011). Sarkono et al . (2010) isolated four
culturable presumptive LAB strains, identified as members of the genus Lactobacillus ,from
the fluid of the digestive tract of abalone ( Haliotis asinina ). However, identification was only
based on cell shape, Gram reaction, catalase, motility and endospore formation. The LAB
isolates were also tested for their ability to inhibit in vitro growth of Escherichia coli , Staphy-
lococcus aureus and Bacillus cereus , but as the inhibition zones were generally low no clear
conclusion could be drawn.
It should be noted that certain species of LAB detected in shellfish could poten-
tially be causative agents of disease. For example, Cheng and Chen (1998) identified an
Enterococcus -like bacterium closely related to E. seriolicida which was detected in diseased
Macrobrachium rosenbergii and caused 100% mortality when injected into healthy shrimp.
Similar disease effects appear to be caused by another LAB, Lc. lactis , which in a separate
study was isolated from diseased M. rosenbergii and identified as a disease causing bacteria
which resulted in 100% mortality in 2 days (Wang etal . 2008). Shellish may also harbour LAB
which are known human pathogens. In a recent study Uaboi-Egbenni et al . (2010) isolated a
well-known pathogen, Str. agalactiae , from natural populations. Thus any potential probiotics
isolated from shellfish should be tested for their pathogenicity to humans. It is clear from the
limited data available that more studies are required to assess the levels, composition and func-
tionality of LAB in shellfish. Future studies should investigate the full microbial community
and not merely seek to isolate a limited number of LAB isolates for potential use as probiotics.
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