Effects of Ceftiofur and Chlortetracycline on the Resistome of Feedlot Cattle.

Effects of Ceftiofur and Chlortetracycline on the Resistome of Feedlot Cattle. Appl Environ Microbiol. 2018 May 04;: Authors: Weinroth MD, Scott HM, Norby B, Loneragan GH, Noyes NR, Rovira P, Doster E, Yang X, Woerner DR, Morley PS, Belk KE Abstract Treatment of food producing animals with antimicrobial drugs (AMD) is controversial because of concerns regarding promotion of antimicrobial resistance (AMR). To investigate this concern, resistance genes in metagenomic bovine fecal samples during a clinical trial were analyzed to assess the impacts of treatment on beef feedlot cattle resistomes. Four groups of cattle were exposed, using a 2x2 factorial design, to different regimens of antimicrobial treatment. Injections of ceftiofur crystalline free acid (a third generation cephalosporin) were used to treat all cattle in treated pens vs. only a single animal, and chlortetracycline was included in the feed of all cattle in a pen vs. no treatment. On days 0 and 26, respectively, pre- and post-trial fecal samples were collected and resistance genes were characterized using shotgun metagenomics. Treatment with ceftiofur was not associated with changes to β-lactam resistance genes. However, cattle fed chlortetracycline had a significant increase in relative abundance of tetracycline resistance genes. There was also an increase of an AMR class not administered during the study-a possible indicator of co-selection of resistance genes. Samples ...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Tags: Appl Environ Microbiol Source Type: research