523
vesiculation, i.e. protrusions on the plasma membrane which became detected as
particles, and necrosis in nucleated sea bream erythrocytes (Wong et al. 2012 ).
The LuxS quorum sensing system, which regulates the expression of some virulence factors, has been studied in V. alginolyticus when mutations in the luxS gene
led to reduced virulence. The mutants had reduced growth rates, defective fl agellar
synthesis, decreased protease production but enhanced extracellular polysaccharide
production and biofi lm development. The interpretation was that the LuxS quorum
sensing system regulated the expression of virulence factors in the pathogen (Ye
et al. 2008 ).
Disease Control
Vaccine Development A DNA vaccine was constructed containing the fl agellin
fl aA gene from a culture of V. alginolyticus and used i.m. (8 μg/fi sh) in red snapper
( Lutjanus sanguineus ) with results showing a wide distribution of the antigens to
the gill, kidney, liver, spleen and muscle around the injection site with expression of
the fl aA gene after 7–28 days with a RPS after challenge of 88 % (Liang et al. 2011 ).
Also, recombinant fl aC was a worthy vaccine candidate with a resulting RPS of
84 % (Liang et al. 2010 ). A combination vaccine with inactivated cells of V. alginolyticus , V. harveyi , V. vulnifi cus and infectious spleen and kidney necrosis virus was
evaluated in orange-spotted grouper ( Epinephelus coioides) with an overall RPS of
80 % (Huang et al. 2012 ).
A conserved OMP, OmpK, administered i.p. at 100 μg protein/fi sh and boosted
after 2-weeks protected large yellow croakers (RPS = 70–79 %) against challenge
4-weeks later (Qian et al. 2008 ).
Immunostimulants/Dietary Supplements Aloe has been found to increase resistance to V. alginolyticus infections in rockfi sh when fed at 5 g aloe/kg of diet for 6
weeks (Kim et al. 1999 ). Chitin and chitosan enriched (1 % and 2 %) diets were fed
to kelp grouper ( Epinephelus bruneus ) leading to immunostimulation (enhanced
albumin, globulin, haematocrit, haemoglobin, erythrocyte and leucocyte count) and
some evidence of protection against challenge, more so with chitosan than chitin
(Harikrishnan et al. 2012a , b , c , d , e ). Aqueous leaf extract of grey/white mangrove
( Avicennia marina ) was fed at 1–8 % to clownfi sh ( Amphiprion sebae ) leading to
immunostimulation and improved survival after challenge. Specifi cally, feeding 1,
4 and 8 % extracts led to survival of 70 %, 85 % and 80 % compared to 10 % surviving in the controls (Dhayanithi et al. 2015a ). Extract of leaves from another mangrove Rhizophora apiculata was fed at 5 % and 10 % also to clownfi sh, ( Amphiprion
sebae ) when improved growth, immunostimulation (superoxide anion production,
and anti-protease, bacteriocidal, complement, lysozyme, phagocytic and respiratory
burst activities) and protection against challenge (with 5 % mangrove extract, the
survival rate was 85 %) were reported (Dhayanithi et al. 2015b ). Katuk ( Sauropus
androgynous ) was fed at 1.0 and 2.5 g/kg for 30 days to grouper juveniles leading
Vibrio alginolyticus
vesiculation, i.e. protrusions on the plasma membrane which became detected as
particles, and necrosis in nucleated sea bream erythrocytes (Wong et al. 2012 ).
The LuxS quorum sensing system, which regulates the expression of some virulence factors, has been studied in V. alginolyticus when mutations in the luxS gene
led to reduced virulence. The mutants had reduced growth rates, defective fl agellar
synthesis, decreased protease production but enhanced extracellular polysaccharide
production and biofi lm development. The interpretation was that the LuxS quorum
sensing system regulated the expression of virulence factors in the pathogen (Ye
et al. 2008 ).
Disease Control
Vaccine Development A DNA vaccine was constructed containing the fl agellin
fl aA gene from a culture of V. alginolyticus and used i.m. (8 μg/fi sh) in red snapper
( Lutjanus sanguineus ) with results showing a wide distribution of the antigens to
the gill, kidney, liver, spleen and muscle around the injection site with expression of
the fl aA gene after 7–28 days with a RPS after challenge of 88 % (Liang et al. 2011 ).
Also, recombinant fl aC was a worthy vaccine candidate with a resulting RPS of
84 % (Liang et al. 2010 ). A combination vaccine with inactivated cells of V. alginolyticus , V. harveyi , V. vulnifi cus and infectious spleen and kidney necrosis virus was
evaluated in orange-spotted grouper ( Epinephelus coioides) with an overall RPS of
80 % (Huang et al. 2012 ).
A conserved OMP, OmpK, administered i.p. at 100 μg protein/fi sh and boosted
after 2-weeks protected large yellow croakers (RPS = 70–79 %) against challenge
4-weeks later (Qian et al. 2008 ).
Immunostimulants/Dietary Supplements Aloe has been found to increase resistance to V. alginolyticus infections in rockfi sh when fed at 5 g aloe/kg of diet for 6
weeks (Kim et al. 1999 ). Chitin and chitosan enriched (1 % and 2 %) diets were fed
to kelp grouper ( Epinephelus bruneus ) leading to immunostimulation (enhanced
albumin, globulin, haematocrit, haemoglobin, erythrocyte and leucocyte count) and
some evidence of protection against challenge, more so with chitosan than chitin
(Harikrishnan et al. 2012a , b , c , d , e ). Aqueous leaf extract of grey/white mangrove
( Avicennia marina ) was fed at 1–8 % to clownfi sh ( Amphiprion sebae ) leading to
immunostimulation and improved survival after challenge. Specifi cally, feeding 1,
4 and 8 % extracts led to survival of 70 %, 85 % and 80 % compared to 10 % surviving in the controls (Dhayanithi et al. 2015a ). Extract of leaves from another mangrove Rhizophora apiculata was fed at 5 % and 10 % also to clownfi sh, ( Amphiprion
sebae ) when improved growth, immunostimulation (superoxide anion production,
and anti-protease, bacteriocidal, complement, lysozyme, phagocytic and respiratory
burst activities) and protection against challenge (with 5 % mangrove extract, the
survival rate was 85 %) were reported (Dhayanithi et al. 2015b ). Katuk ( Sauropus
androgynous ) was fed at 1.0 and 2.5 g/kg for 30 days to grouper juveniles leading
Vibrio alginolyticus