544
Inhibitors of Quorum Sensing V. anguillarum produces quorum sensing molecules,
which may well be involved with the regulation of virulence. If these molecules could
be blocked using quorum sensing inhibitors, then virulence could be reduced or even
annulled. Funanone C-30, dosed at 0.01 or 0.1 μM. was determined to be benefi cial at
reducing mortalities caused by cohabitation with V. anguillarum infected rainbow
trout from 80–100 % in the controls to 4–40 % in treated groups (Rasch et al. 2004 ).
Bacteriophage Therapy Two bacteriophage preparations (10
8 PFU/ml) were
applied to tank water, and controlled V. anguillarum infection in zebra fi sh (Silva
et al. 2014 ).
Antimicrobial Compounds Antimicrobial compounds, including fl orfenicol
(Seljestokken et al. 2006 ) have proved to be very useful in controlling vibriosis. It
is perhaps ironic that emphasis has been placed on using drugs as food additives,
because vibriosis is typifi ed by inappetance. Consequently, antimicrobial compounds need to be administered (by food) very early in the disease cycle, if success
is to be achieved. Workers have indicated the value of many compounds, including
chloramphenicol, fl umequine (Vik-Mo et al. 2005 ), furanace, nitrofurazone, oxolinic acid, oxytetracycline and sulphamerazine. As a general comment, we advise
upon caution when contemplating the need for pharmaceuticals, particularly antibiotics, because of the potential risk of resistance which may be attributed to plasmids, i.e. R factors (Aoki 1988 ). Aoki et al. ( 1974 ) reported that 65/68 V. anguillarum
isolates carried R factors, conveying resistance to chloramphenicol, streptomycin,
sulphonamides and tetracycline. Therefore if R factors abound, it is unlikely that the
common antibiotics will do much to retard the disease cycle.
Another approach has involved the use of antimicrobial peptides, namely a
cecropin-melittin hybrid peptide and pleurocidin amide, which is a C-terminally
amidated form of a natural fl ounder peptide. These were applied continuously at a
rate of 200 μg/day and 250 μg/for for cecropin-melittin hybrid peptide and pleurocidin amide respectively by miniosmotic pumps installed in the peritoneal cavity of
coho salmon with the result that less mortalities occurred compared to the controls.
In the case of pleurocidin amide, 5 % mortalities were recorded compared to
67–75 % of the controls (Jia et al. 2000 ).
Vibrio cholerae (non-O1)
Characteristics of the Disease
During the summer of 1977, an epizootic occurred in a wild population of ayu in the
River Amano, Japan. From diseased animals, an organism conforming to the
description of V. cholerae was isolated (Muroga et al. 1979 ; Kiiyukia et al. 1992 ).
Subsequently, V. cholerae was associated with a disease of goldfi sh in Australia
10 Vibrios
Inhibitors of Quorum Sensing V. anguillarum produces quorum sensing molecules,
which may well be involved with the regulation of virulence. If these molecules could
be blocked using quorum sensing inhibitors, then virulence could be reduced or even
annulled. Funanone C-30, dosed at 0.01 or 0.1 μM. was determined to be benefi cial at
reducing mortalities caused by cohabitation with V. anguillarum infected rainbow
trout from 80–100 % in the controls to 4–40 % in treated groups (Rasch et al. 2004 ).
Bacteriophage Therapy Two bacteriophage preparations (10
8 PFU/ml) were
applied to tank water, and controlled V. anguillarum infection in zebra fi sh (Silva
et al. 2014 ).
Antimicrobial Compounds Antimicrobial compounds, including fl orfenicol
(Seljestokken et al. 2006 ) have proved to be very useful in controlling vibriosis. It
is perhaps ironic that emphasis has been placed on using drugs as food additives,
because vibriosis is typifi ed by inappetance. Consequently, antimicrobial compounds need to be administered (by food) very early in the disease cycle, if success
is to be achieved. Workers have indicated the value of many compounds, including
chloramphenicol, fl umequine (Vik-Mo et al. 2005 ), furanace, nitrofurazone, oxolinic acid, oxytetracycline and sulphamerazine. As a general comment, we advise
upon caution when contemplating the need for pharmaceuticals, particularly antibiotics, because of the potential risk of resistance which may be attributed to plasmids, i.e. R factors (Aoki 1988 ). Aoki et al. ( 1974 ) reported that 65/68 V. anguillarum
isolates carried R factors, conveying resistance to chloramphenicol, streptomycin,
sulphonamides and tetracycline. Therefore if R factors abound, it is unlikely that the
common antibiotics will do much to retard the disease cycle.
Another approach has involved the use of antimicrobial peptides, namely a
cecropin-melittin hybrid peptide and pleurocidin amide, which is a C-terminally
amidated form of a natural fl ounder peptide. These were applied continuously at a
rate of 200 μg/day and 250 μg/for for cecropin-melittin hybrid peptide and pleurocidin amide respectively by miniosmotic pumps installed in the peritoneal cavity of
coho salmon with the result that less mortalities occurred compared to the controls.
In the case of pleurocidin amide, 5 % mortalities were recorded compared to
67–75 % of the controls (Jia et al. 2000 ).
Vibrio cholerae (non-O1)
Characteristics of the Disease
During the summer of 1977, an epizootic occurred in a wild population of ayu in the
River Amano, Japan. From diseased animals, an organism conforming to the
description of V. cholerae was isolated (Muroga et al. 1979 ; Kiiyukia et al. 1992 ).
Subsequently, V. cholerae was associated with a disease of goldfi sh in Australia
10 Vibrios