| Abstrakt: |
Florfenicol (FFC) is a broad‐spectrum antibiotic approved by the U.S. Food and Drug Administration to treat both systemic and external bacterial infections in food fish. The objective of this study was to evaluate the effect of FFC‐medicated feed on the gut microbiota of Zebrafish Danio danioto determine (1) if the therapeutic dose of FFC‐medicated feed induces dysbiosis and (2) if fish with altered gut microbiota were more susceptible to subsequent infection by the common opportunistic fish pathogen Aeromonas hydrophila. Zebrafish that were treated with regular and FFC‐medicated feeds were artificially challenged with A. hydrophilaat the end of the recommended 15‐day antibiotic withdrawal period. The gut microbiota of the Zebrafish at different stages was analyzed using 16S ribosomal RNA gene sequencing. Our results found that FFC‐medicated feed induced disruption of the gut microbiota. Dysbiosis was observed in all treated groups, with a significant increase in bacterial diversity, and was characterized by a remarkable bloom of Proteobacteria and a drastic decline of Mycoplasmaand Cetobacteriumin treated animals but without noticeable clinical signs or mortalities. In addition, the increase of Proteobacteria was not significantly reduced after the recommended 15‐day withdrawal period, and the Zebrafish treated with FFC‐medicated feed exhibited a significantly higher mortality rate when they were subsequently challenged with A. hydrophilacompared to the control (regular feed) groups. Interestingly, the most dramatic changes in the gut microbiome composition occurred at the transition time between the late stage of the medicated treatment and the beginning of the withdrawal period instead of the time during the Aeromonasinfection. The administration of FFC‐medicated feed at the recommended dose induced gut dysbiosis in Zebrafish, and fish did not recover to the baseline after the recommended withdrawal period. Our findings suggest that the use of antibiotics in fish elicits a response similar to those previously described in mammals and possibly makes the host more susceptible to subsequent infections of opportunistic pathogens. This study using a controlled model system suggests that antibiotics in aquaculture may have long‐term effects on the general well‐being of the fish. Impact statementOur results suggested that bacterial community in the gut of healthy Zebrafish could be readily disturbed as a result of antibiotic administration. In addition, after medicated feed, Zebrafish were more susceptible to bacterial secondary infection (e.g., Aeromonas hydrophila). Our results suggested that bacterial community in the gut of healthy Zebrafish could be readily disturbed as a result of antibiotic administration. In addition, after medicated feed, Zebrafish were more susceptible to bacterial secondary infection (e.g., Aeromonas hydrophila). |
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