We are looking for strains - either clinical or from laboratory collections - of Salmonella enterica - different serovars - with plasmid-borne resistance to fluoroquinolones. Strains with presumptively plasmidic resistance, e.g. confirmed to have qnrB gene, would work. Escherichia coli strains with plasmid-borne fluoroquinolone resistance are also of interest. The strains are sought for pharmacodynamic experimentation.