Abalone aquaculture subprogram: potential for antibiotic use in abalone for disease control

OBJECTIVES:
1. To confirm the potential for antibiotic control of bacterial infections of abalone
2. To determine which antibiotics are most suitable for use in abalone aquaculture and appropriate mechanisms of delivery.
3. Coincidentally to increase understanding of factors affecting V. harveyi infections in abalone, and provide tools for further research into its control.

OUTCOMES ACHIEVED
Of the 5 antibiotics tested, only oxytetracycline was confirmed as being adequately absorbed and clinically active when milled into feed, with efficacy demonstrated against V. harveyi, the major pathogen of immediate concern. Absorption of this antibiotic from food was moderate, and residue clearance remains a concern. Absorption of all antibiotics from agar coated food was significantly lower than treatments milled into the feed. A relatively small Absorption of this antibiotic by bath Absorption of other antibiotics was poor, with the exception of bath absorption of oxolinic acid, which is no longer acceptable for food producing animals, and
moderate levels of sulphadiazine from bath treatment. However as sulphonamides are unlikely to be used alone, and trimethoprim was ineffective in trials against V. harveyi, this provides little opportunity for use unless further work identifies a more useful potentiator. Knowledge of the characteristics of V. harveyi infection and dynamics of innate bacterial factors was also gained.