DuP 721 Resistance in Escherichia Coli Strain E2295 (45-5) Results from the Modification of a Bacterial Translation Component
DuP 721, a compound belonging to a new class of synthetic antibacterial agents, the oxazolidinones, could potentially become an important agent in controlling infections caused by certain gram positive pathogens, especially those resistant to antibiotics commonly used in clinical settings. Preliminary studies indicate that the primary action of DuP 721 is on protein synthesis, but it is not clear which steps in transcription/translation are affected. The focus of this project was to determine whether the resistance phenotype generated in an Escherichia coli strain against DuP 721 resulted from the modification of an intracellular target or from a defect in the ability of the bacterium to take up the drug. Cell-free extracts from a DuP 721-sensitive strain and from a DuP 721-resistant strain were prepared by the method of Zubay (Pratt 1984). The amount of protein synthesized in each extract in the absence and presence of antibiotic was determined. [35S] methionine was used as the sole source of methionine to detect protein synthesis directed by a defined DNA template. The translation products were also analyzed by SDS polyacrylamide gel electrophoresis. Results described in this report indicate that cell extracts prepared from the DuP 721-sensitive strain were translationally less active in the presence of the antibiotic than extracts from DuP 721-resistant strains. These data indicate that strain E2295 (45-5) resistance to DuP 721 in vivo is not due to decreased drug uptake, but to the modification of a target in the transcription/ translation apparatus normally susceptible to DuP 721. Biochemical and genetic studies may result in identification of oxazolidinone mode of action.
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