Certain farming practice widely perceived as beneficial may actually has undesirable effects on therapy. The probiotics are commonly supplemented in aquaculture owing to their modulatory improvements on growth performances, immunity, intestinal microbiome, disease resistance and water quality. However, before probiotics can serve as a single treatment for disease therapy, its effect on antibiotic therapy cannot be assumed beneficial and warrants investigation.
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. Steady state serum FF concentration (shown as day 1 concentration after the last dose) was 3.5 folds lower (1.79 vs 6.27 µg/mL) in the probiotic-treated fish (P<0.05). The production of FF amine (FFA) was also reduced by 4 folds (0.14 vs 0.63 µg/mL) in the probiotic group, the averaged FFA/FF ratio was slightly smaller (40% reduction) (Table 1).
To elucidate whether significantly reduced serum FF concentration was associated with reduced gut absorption, the concentration-time profile of FF after single IV injection (10 mg/kg) and a 2-compartmental model PK analysis was performed. There were little differences on most parameters, except for slightly faster drug elimination in the probiotic group. The results suggested that the reduced serum FF concentration was more likely associated with the reduced absorption of FF from the gut rather than increased metabolism in the liver.
Therefore, the intake of probiotics might cause undesirable effect on FF therapy, as it reduced serum drug concentrations required for effective treatment of infection.