Impact_of_enrofloxacin_on_human_intestianl_microbiota
Impact of enrofloxacin on the human intestinal microbiota revealed by comparative molecular analysis
The indigenous human intestinal microbiota and the protective barrier formed by microbiota in gastrointestinal tract could be disrupted by residues of antibiotics in foods as well as antibiotics therapeutically administrated to humans. These disruptions may lead to adverse health outcomes. To observe the possible impact of residues of antibiotics on human intestinal microbiota, we performed studies using an in vitro culture of fecal suspensions from three individuals with 10 different concentrations (0, 0.1, 0.5, 1, 5, 10, 15, 25, 50 and 150 g/ml) of the fluoroquinolone, enrofloxacin. The bacterial communities of the control and enrofloxacin dosed fecal samples were analyzed by denaturing gradient gel electrophoresis (DGGE) and pyrosequencing. In addition, changes of functional gene expression were analyzed by pyrosequencing-based random whole-community mRNA sequencing method. The compositional taxonomic analyses were performed with a total of 199,007 pyrosequencing reads and the gene expressions of microbiota were analyzed with a total of 279,585 reads. Although each individual has their unique microbial compositions, the communities of all individuals were affected by enrofloxacin. The proportions of two phyla, Bacteroidetes and Proteobacteria, were significantly reduced with increasing concentrations of enrofloxacin exposure, while the proportion of Firmicutes increased. Principal Coordinate Analysis (PCA) using Fast UniFrac indicated the community structures of intestinal microbiota were shifted by enrofloxacin. Most of the mRNA transcripts and the resistance genes increased at increasing concentration of enrofloxacin. 16S rRNA gene pyrosequencing of control and enrofloxacin treated fecal suspensions provided valuable information of affected bacterial members down to the species level, and the community transcriptomic analyses using mRNA revealed the functional gene expression responses of changed community by enrofloxacin.