Probiotic pretreatment reduced the florfenicol concentration and shortened the withdrawal time in Asian seabass (Lates calcarifer) presumably by decreasing drug absorption.

The present study investigated the effect of probiotic pretreatment on the pharmacokinetics (PK) of florfenicol (FF) in Asian seabass (Lates calcarifer) reared at 25℃. Healthy fish were fed with a mixture of Lactobacillus delbrueckii and Lacticaseibacillus rhamnosus suspension for 10 days followed by oral gavage of 10 mg/kg/day FF for 5 days. The serum and muscle/skin FF concentrations were analyzed by HPLC-FLD on days 1, 3, and 5 after the last dose. In comparison to the control group, serum FF concentration in the probiotic group was 2.45 folds lower at day 1 of drug withdrawal (steady state). Similarly, florfenicol amine concentration was also significantly lower in the serum and muscle/skin at day 1. The lowered tissue concentration resulted in a shortened withdrawal time (6 to 4 days). To delineate the involvement of probiotic action at the gut level, the intravenous PK of FF was performed and indicated that serum FF concentration was consistently higher in the probiotic group, while the elimination half-life was significantly lower. Thus, it was assumed that a probiotic-drug interaction that leads to reduced intestinal absorption might be responsible for the decreased FF concentration following probiotic supplementation and may necessitate a higher antibiotic dose for effective treatment.