Horizontal Gene Transfer Is the Main Driver of Antimicrobial Resistance in Broiler Chicks Infected with Salmonella enterica Serovar Heidelberg
Adelumola Oladeinde, Zaid Abdo, Maximilian O. Press, Kimberly Cook, N.A. Cox, Benjamin Zwirzitz, Reed Woyda, Steven M. Lakin, Jesse C. Thomas, Torey Looft, D.E. Cosby, Arthur Hinton, Jean Guard, Eric Line, Michael J. Rothrock, M.E. Berrang, Kyler Herrington, Gregory Zock, Jodie Plumblee Lawrence, Denice Cudnik, Sandra L. House, Kimberly D. Ingram, Leah Lariscy, Martin Wagner, Samuel E. Aggrey, Lilong Chai, Casey W. Ritz
Abstract
The reported increase in antibiotic-resistant bacteria in humans has resulted in a major shift away from antibiotic use in food animal production. This shift has been driven by the assumption that removing antibiotics will select for antibiotic susceptible bacterial taxa, which in turn will allow the currently available antibiotic arsenal to be more effective. This change in practice has highlighted new questions that need to be answered to assess the effectiveness of antibiotic removal in reducing the spread of antibiotic resistance bacteria. This research demonstrates that antibiotic-susceptible Salmonella enterica serovar Heidelberg strains can acquire multidrug resistance from commensal bacteria present in the gut of neonatal broiler chicks, even in the absence of antibiotic selection. We demonstrate that exposure to acidic pH drove the horizontal transfer of antimicrobial resistance plasmids and suggest that simply removing antibiotics from food animal production might not be sufficient to limit the spread of antimicrobial resistance.