Sub-chronic exposure to antibiotics doxycycline, oxytetracycline or florfenicol impacts gut barrier and induces gut microbiota dysbiosis in adult zebrafish (Daino rerio)

Antibiotics are widely used in the treatment of bacterial infections and as food additives in the livestock industry. The wide usage of antibiotics causes residues in animal products, like milk, eggs and meat. A number of studies have reported that antibiotic residues exist at high concentrations in watercourses around the world. Doxycycline (DH), oxytetracycline (OTCC) and florfenicol (FF) are the three most commonly used veterinary antibiotics in China. However, studies of the toxic effects of DH, OTCC and FF are limited. In this study, six-moth-old healthy male adult zebrafish were exposed to 0, 10, 30, 100 mu g/L DH, OTCC or FF for 21 days. After exposure, some biochemical parameters changed significantly, including total cholesterol (TC), triglyceride (TG), pyruvate and acid phosphatase (ACP). In addition, mucus secretion in the gut decreased and the transcription of related genes also decreased significantly. Moreover, the composition of microbiota in the gut changed significantly. DH, OTCC and FF exposure caused the decrease of diversity of gut microbiota. The relative abundance of Proteobacteria increased significantly after OTCC and FF exposure and Fusobacteria decreased in all antibiotic-treated groups. Further functional prediction analysis also suggested changes in gut microbiota in the OTCC and FF-treated groups, especially those linked to metabolism. To support this idea, we confirmed that some glycolipid related genes also increased significantly in the liver of adult zebrafish after antibiotic exposure. According to these results, DH, OTCC or FF exposure could cause the gut microbiota dysbiosis and dysfunction, and hepatic metabolic disorder in adult male zebrafish.