In-feed administered sub-therapeutic chlortetracycline alters community composition and structure but not the abundance of community resistance determinants in the fecal flora of the rat.

摘要: Abstract The impact of continuous sub-therapeutic chlortetracycline on community structure, composition and abundance tetracycline resistance genes in the rat fecal was investigated. Rats were fed a standard diet containing at 15 μg g −1 for 28 days, followed by 30 μg g to completion study day-56. These levels are similar those administered swine during grow-out phase. Sub-therapeutic affected as determined through change cultivable anaerobic molecular-based analyses including denaturing gradient gel electrophoresis profiles variable 2–3 region 16S rRNA over time comparative sequence analysis gene libraries. Significant decreases phylotype diversity occurred response chlortetracycline, although total bacterial output remained constant entire feeding trial. Chlortetracycline resulted significant composition, but only modest structure terms distribution individual phylotypes among major lineages. significantly altered lineages shifting overall such that Gram-negative aligning within phylum Bacteroidetes became dominant lineage (>60% community). While impacted both there no effect [ tet (Q), (W), (O)] or emergence new putative identified community. provides sufficient selective pressure alter community, primary outcome appears be development which may have higher inherent tolerance rather than an overgrowth resistant bacteria already present