Temporal changes in antimicrobial resistance of fecal coliforms isolated from dairy cows

Antimicrobial resistance is a growing concern in both food animal and public health. However, the role of antimicrobial use and management practices used on livestock operations on the accumulation, dissemination, and persistence of resistance has not been clearly determined. Most studies on antimicrobial resistance were conducted as cross-sectional observational studies; therefore, little is known about the dynamics of antimicrobial resistance in an animal as it transitions through various production phases or the impact of antimicrobial treatments on resistance over time. The goals of this study were to determine temporal changes in the quantities of susceptible and resistant coliform bacteria to four antimicrobials in fecal samples that were collected throughout a full production cycle, and to determine whether health or performance events affect the quantity or patterns of antimicrobial-resistant bacteria in dairy cattle.