Rifampicin Resistant Mutants of Salmonella enterica and Escherichia coli

Rifampicin resistant mutants of Salmonella and E. coli were created for the testing of contamination in agricultural environments or products where natural E. coli and Salmonella may be present; rifampicin resistance allows for differentiation between natural and inoculated, laboratory-based strains via selective media. The Salmonella wild type strains, including two representatives of serovar Newport and one belonging to serovar Oranienburg, were obtained from Oregon Health Authority and passaged on rifampicin-containing agar plates to induce resistance. E. coli mutants were derived similarly from strains collected from irrigation water, lettuce, and sandy loam soils using similar methods performed by another laboratory (Trevor Suslow - University of California, Davis; strains provided by Linda Harris).