296
having promise. Subsequently, polymyxin B nonapeptide has been found to inhibit
Aer. salmonicida, probably by disrupting the A-layer (McCashion and Lynch,1987).
Curiously, the use of some compounds follows a geographical pattern, e.g. in
France fl umequine (a quinolone) is favoured (Michel et al. 1980 ), whereas in
England and Japan, oxolinic acid has been used extensively (see Endo et al. 1973 ;
Austin et al. 1983b ). It is debatable as to whether fl umequine or oxolinic acid has
been more successful at combating furunculosis (Barnes et al. 1991a ). Additionally
in England, potentiated sulphonamides have been used widely (McCarthy et al.
1974 ). Within the UK, four compounds, namely amoxicillin, oxolinic acid, oxytetracycline and potentiated sulphonamides, are currently licensed for fi sheries use in
the treatment of furunculosis. For other diseases caused by Aer. salmonicida, i.e. CE
and goldfi sh ulcer disease, less information is available. It appears, however, that
potentiated sulphonamides and oxytetracycline are generally effective against the
pathogen, regardless of the disease manifestation and assuming that treatment
begins at an early stage in the disease cycle (Gayer et al. ( 1980 ). Unfortunately
despite its comparatively recent arrival in the armoury of fi sheries chemotherapeutants, resistance to amoxicillin has been documented in Scotland (Barnes et al.
1994 ). For the future, fl orfenicol, dosed at 10 mg/kg body weight of fi sh/day for 10
days, offers promise, insofar as it has already been used with some success against
furunculosis in Norway (Nordmo et al. 1994 ; Samuelsen et al. 1998 ).
Since the initial work with oxolinic acid (Endo et al. 1973 ; Austin et al. 1983 ), it
is apparent that substantial quantities have been used in aquaculture within many
countries. Consequently, it is hardly surprising that resistant strains of Aer. salmonicida have emerged (Hastings and McKay 1987 ; Tsoumas et al. 1989 ; Barnes et al.
1990a , b). Yet, the widespread usefulness of the compound at controlling furunculosis has prompted a search for other related compounds. The fruits of this research
may be illustrated by the apparent success of 4-quinolones/fl uoroquinolones at
inhibiting the pathogen (Barnes et al. 1990a , b, 1991b ; Bowser and House 1990 ;
Lewin and Hastings 1990 ; Martinsen et al. 1991 ; Inglis and Richards 1991 ;
Stoffregen et al. 1993 ; Elston et al. 1995 ). Thus, enrofl oxacin and sarofl oxacin have
been found to be more effective than oxolinic acid, in terms of MIC at inactivating
Aer. salmonicida. The effectiveness of enrofl oxacin at 10 mg/kg body weight of
fi sh/day for 10 days has been attested by fi eld trials with lake trout ( Salvelinus
namaycush ) (Hsu et al. 1995 ). In addition, enrofl oxacin has been effective in controlling atypical Aer. salmonicida in tom cod, insofar as a single injection with 5 mg
of enrofl oxacin/kg of fi sh stopped furunculosis (Williams et al. 1997 ). Difl oxacin,
dosed at 5 or 10 days at 5 mg/kg body weight, and 10 days at 1.25 or 2.5 mg/kg body
weight resulted in signifi cantly lowered mortalities compared to controls following
i.m. injection with a virulent culture of Aer. salmonicida. Of relevance, there was
little difference in the results between 5 and 10 day treatment regimes with 5 mg/ kg
body weight (Elston et al. 1995 ).
With the realisation that Aer. salmonicida occurs on the external surfaces, i.e.
gills and mucus, attempts have been made at disinfection. Cipriano et al. ( 1996c , d )
evaluated chloramine T, dosed at 15 mg/l for 60 min on three consecutive days, but
5 Aeromonadaceae Representative (Aeromonas salmonicida)
having promise. Subsequently, polymyxin B nonapeptide has been found to inhibit
Aer. salmonicida, probably by disrupting the A-layer (McCashion and Lynch,1987).
Curiously, the use of some compounds follows a geographical pattern, e.g. in
France fl umequine (a quinolone) is favoured (Michel et al. 1980 ), whereas in
England and Japan, oxolinic acid has been used extensively (see Endo et al. 1973 ;
Austin et al. 1983b ). It is debatable as to whether fl umequine or oxolinic acid has
been more successful at combating furunculosis (Barnes et al. 1991a ). Additionally
in England, potentiated sulphonamides have been used widely (McCarthy et al.
1974 ). Within the UK, four compounds, namely amoxicillin, oxolinic acid, oxytetracycline and potentiated sulphonamides, are currently licensed for fi sheries use in
the treatment of furunculosis. For other diseases caused by Aer. salmonicida, i.e. CE
and goldfi sh ulcer disease, less information is available. It appears, however, that
potentiated sulphonamides and oxytetracycline are generally effective against the
pathogen, regardless of the disease manifestation and assuming that treatment
begins at an early stage in the disease cycle (Gayer et al. ( 1980 ). Unfortunately
despite its comparatively recent arrival in the armoury of fi sheries chemotherapeutants, resistance to amoxicillin has been documented in Scotland (Barnes et al.
1994 ). For the future, fl orfenicol, dosed at 10 mg/kg body weight of fi sh/day for 10
days, offers promise, insofar as it has already been used with some success against
furunculosis in Norway (Nordmo et al. 1994 ; Samuelsen et al. 1998 ).
Since the initial work with oxolinic acid (Endo et al. 1973 ; Austin et al. 1983 ), it
is apparent that substantial quantities have been used in aquaculture within many
countries. Consequently, it is hardly surprising that resistant strains of Aer. salmonicida have emerged (Hastings and McKay 1987 ; Tsoumas et al. 1989 ; Barnes et al.
1990a , b). Yet, the widespread usefulness of the compound at controlling furunculosis has prompted a search for other related compounds. The fruits of this research
may be illustrated by the apparent success of 4-quinolones/fl uoroquinolones at
inhibiting the pathogen (Barnes et al. 1990a , b, 1991b ; Bowser and House 1990 ;
Lewin and Hastings 1990 ; Martinsen et al. 1991 ; Inglis and Richards 1991 ;
Stoffregen et al. 1993 ; Elston et al. 1995 ). Thus, enrofl oxacin and sarofl oxacin have
been found to be more effective than oxolinic acid, in terms of MIC at inactivating
Aer. salmonicida. The effectiveness of enrofl oxacin at 10 mg/kg body weight of
fi sh/day for 10 days has been attested by fi eld trials with lake trout ( Salvelinus
namaycush ) (Hsu et al. 1995 ). In addition, enrofl oxacin has been effective in controlling atypical Aer. salmonicida in tom cod, insofar as a single injection with 5 mg
of enrofl oxacin/kg of fi sh stopped furunculosis (Williams et al. 1997 ). Difl oxacin,
dosed at 5 or 10 days at 5 mg/kg body weight, and 10 days at 1.25 or 2.5 mg/kg body
weight resulted in signifi cantly lowered mortalities compared to controls following
i.m. injection with a virulent culture of Aer. salmonicida. Of relevance, there was
little difference in the results between 5 and 10 day treatment regimes with 5 mg/ kg
body weight (Elston et al. 1995 ).
With the realisation that Aer. salmonicida occurs on the external surfaces, i.e.
gills and mucus, attempts have been made at disinfection. Cipriano et al. ( 1996c , d )
evaluated chloramine T, dosed at 15 mg/l for 60 min on three consecutive days, but
5 Aeromonadaceae Representative (Aeromonas salmonicida)