28th ANNUAL EASTERN FISH HEALTH WORKSHOP
April 21-25, 2003
Laboratory Efficacy Of Amoxicillin For
The Control Of Streptococcus iniae
Infection In Hybrid Striped (Sunshine) Bass
Ahmed M. Darwish
Harry K. Dupree-Stuttgart National
Aquacutlure Research Center, United States Department of Agriculture,
Agriculture Research Service, P. O. Box 1050, Stuttgart, Arkansas, 72160
Experimental trial was performed to
evaluate the efficacy of amoxicillin (AMX) in controlling Streptococcus iniae infection in hybrid striped bass (Morone chrysops female
´ Morone
saxatilis
male). Minimum-inhibitory concentration
studies of AMX against multiple S. iniae isolates showed a
sensitivity range of 0.0156 to 0.5 mg/mL. Amoxicillin dose levels tested were 30, 50,
80 and 120 mg active ingredient per kilogram of fish body weight per day. Administration of medicated feed started 1 d
after infection by waterborne exposure to S.
iniae and continued for 8 consecutive days, followed by 15 d post-treatment
observation. The AMX increased the
survival rate from 1 % in the infected non-treated group to a survival average
of 95 % in the fish groups receiving the four AMX doses with no significant
difference among the AMX medicated groups. Survivors of the infection were not detected to be carriers of the
bacteria (negative bacterial isolation).
