Effects of a Direct-Fed Microbial and Feedlot Pen Environmental Change on Phenotypic Resistance among Enterococci Isolated from Beef Cattle Feces

• DOI: 10.20944/preprints202111.0474.v1
• Publication Date: 2021-11-26T11:35:32Z
• Authors: Sarah A. Murray; Ashlyn C. Holbert; Keri N. Norman; Sara D. Lawhon; Jason E. Sawyer; Harvey Morgan Scott
• Keywords: Feedlot; Enterococcus faecium; Tylosin; Beef Cattle; Enterococcus faecalis

In two sequential replicates (n=90 and n=96 feedlot finisher cattle, respectively) we measured the impact of an Enterococcus faecium-based probiotic (DFM) altered pen environment on antimicrobial resistance among fecal enterococci in cattle fed (or, not fed) macrolide tylosin. Diluted samples were spiral-plated plain antibiotic-supplemented m-Enterococcus agar. first replicate, tylosin significantly (p<0.05) increased relative quantity erythromycin-resistant enterococci. This effect was diminished DFM conjunction with A similar observed statistically significant (P > 0.05) second replicate. Isolates speciated phenotypes obtained for E. faecium hirae. isolates whole-genome sequenced, which yielded sequence types (ST), genes phylogeny. Samples sequenced found to contain ST296, present Day 0 either type after 0, majority isolated from one DFM-fed pens. Increased prevalence ST296 occurred a concomitant decrease ST240; importance, latter typically harbored both ermB tet(M) genes.