Dietary supplement of probiotics as feed additive is becoming a common practice in aquaculture. While the majority of studies mainly focus on the beneficial effects of probiotics in aquaculture, few studies concern the “adverse effect” of probiotic supplement that may reduce the efficacy of the drug treatment. The study of the effect of probiotics on the pharmacokinetics of antibiotics may open a new and more complete overview of the advantageous use of probiotics in aquaculture
Florfenicol (FF) was orally administered for 5 days at 10 mg/kg/day to 4 Asian seabass pre-treated with saline or Lactobacillus rhamnosus (2.5x107 CFU/fish/day) for 7 days at 25°C. The muscle/skin (in natural proportion) concentrations of FF, FF amine (FFA) and FF+FFA were found consistently about 1.5-2.5 folds lower in the probiotic-treated fish. (Table 1), suggesting that the probiotic treated fish had lower tissue levels of FF and metabolites. Whether or not the drug reduction was a result of reduced gut absorption of increased liver metabolism warrants further elucidation.
The tissue depletion curve of FF+FFA was used to build an estimation of the withdrawal time (WDT) following EMEA standard (with a 95% confidence, the time when the upper one-sided 95% tolerance limit is below the MRL). Under Taiwan governmental regulated dosages of FF at 10 mg/kg for 5 days and MRL of 1 ppm, the WDT in the probiotic-treated fish is 4 days, shortened by 2 days in comparison to the 6 days in the control group.
The 7-day probiotic supplements might beneficially shorten the WDT after FF treatment, but might also undesirably reduce therapeutic efficacy by reducing drug concentrations in Asian seabass.