title: Effect of bacitracin on tetracycline resistance in Escherichia coli and Salmonella.
abstract: Tetracyclines and bacitracin are used extensively as a growth promotant and a therapeutic, respectively in livestock. In this study, we test whether there is an interaction between bacitracin and tetracycline that can select for an increase in microbial tetracycline sensitivity, using Escherichia coli and Salmonella as a model. We found via in vitro studies that bacitracin at sublethal concentrations preferentially selects for outgrowth of tetracycline-sensitive bacteria from among a population of tetracycline-resistant and tetracycline-sensitive E. coli and Salmonella strains. Most of the bacterial strains employed in our study were shown by PCR to possess the tetracycline resistance gene tet(A) or tet(C), either of whose activity is associated with tetracycline efflux. Bacitracin could be substituted for the lipophylic chelator, fusaric acid, used as a positive selective agent for tetracycline sensitivity. Together, these observations suggest that bacitracin-mediated selection for tetracycline sensitivity alters the function of tetracycline efflux proteins. Using bacitracin and tetracycline simultaneously may improve the effectiveness of the antibiotics, while decreasing the risk of selecting for a population of tetracycline-resistant microorganisms.
authors.affiliation: The Center for Infectious Disease Research and Vaccinology, Department of Veterinary Science, South Dakota State University, Brookings, 57007, United States.
authors.forename: Jun
authors.initials: J
authors.lastname: Lin
authors.forename: Teddi
authors.initials: T
authors.lastname: Wolff
authors.forename: Alan
authors.initials: A
authors.lastname: Erickson
authors.forename: David
authors.initials: D
authors.lastname: Francis
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001414:Bacitracin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D012475:Salmonella / Q000187:drug effects*; D013753:Tetracycline Resistance
chemical_list: D000900:Anti-Bacterial Agents; D001414:Bacitracin