Effects of Live Yeast and Yeast Extracts with and without Pharmacological Levels of Zinc on Antimicrobial Susceptibilities of Fecal Escherichia coli in Nursery Pigs

A total of 360 weanling barrows (Line 200 × 400, DNA Genetics; initial BW 12.4 ± 0.05 lb) were used in a 42-d study to evaluate yeast-based pre- and probiotics (Phileo by Lesaffre, Milwaukee, WI) diets with or without pharmacological levels Zn on antimicrobial resistance (AMR) patterns fecal Escherichia coli. Pens assigned 1 4 dietary treatments 5 pigs per pen 18 pens treatment. Dietary arranged 2 factorial main effects live (none vs. 0.10% ActiSafSc 47 HR+, 0.05% SafMannan, NucleoSaf from d 0 7, then concentrations lowered 50% day 7 21) (110 3,000 ppm 2,000 21 provided ZnO). All fed common diet 42 post-weaning Zn. Fecal samples collected 4, 21, the same three for E. coli isolation. The identification was PCR detection uidA clpB genes. AMR determined microbroth dilution method using Sensititre CMV3AGNF panel containing 14 different antimicrobials. addition had marginally significant effect (P = 0.051) increase minimum inhibitory concentration (MIC) values ciprofloxacin; however, median MIC still under Clinical Laboratory Standards Institute (2018) classified resistant breakpoint ciprofloxacin. There no evidence differences > 0.05) yeast additives isolates any remaining antibiotics. In conclusion, tended ciprofloxacin while medians below breakpoint. influence extracts against tested