In agriculture, antibiotics are used for treatment and prevention of livestock disease. Antibiotics perturb the bacterial gut composition but the extent of these changes and potential consequences for animal and human health are still debated. Six calves were housed in a controlled environment. Three animals received an injection of the antibiotic florfenicol (Nuflor) and three received no treatment. Faecal samples were collected at 0, 3, and 7 days, bacterial communities profiled to assess the impact of a therapy on the gut microbiota. Phylogenetic analysis (16S-rDNA) established that at day 7, antibiotic treated microbiota showed a 10-fold increase in facultative anaerobic Escherichia spp, a signature of imbalanced microbiota, dysbiosis. The antibiotic resistome showed a high background of antibiotic resistance genes, which did not significantly change in response to florfenicol. However, the maintenance of Escherichia coli plasmid-encoded quinolone, oqxB and propagation of mcr-2, colistin resistance genes was observed and confirmed by Sanger sequencing. The microbiota of treated animals was enriched with energy harvesting bacteria, common to obese microbial communities. We propose that antibiotic treatment of healthy animals leads to unbalanced, disease- and obese related microbiota that promotes growth of E. coli carrying resistance genes on mobile elements, potentially increasing the risk of transmission of antibiotic resistant bacteria to humans.
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ASJC Scopus subject areas
- Applied Microbiology and Biotechnology