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Radezolid Overcomes CFR-Mediated Linezolid-Resistance by Efficiently Inhibiting Protein Synthesis on CFR-Methylated Ribosomesтезисы доклада
- Авторы: FRANCESCHI F., DEVITO J., DALTON J., REMY J., SKRIPKIN E., IPPOLITO J., DUFFY E.
- Сборник: 50th ICAAC Meeting, Sept. 12-15, 2010
- Тезисы
- Год издания: 2010
- Место издания: ASM Boston, Massachusetts
- Первая страница: C1-095
- Аннотация: Background: Radezolid (RDZ) is an investigational oxazolidinone active against a variety of Gram-positive bacteria, including MRSA. RDZ overcomes the main cause of target-base linezolid (LZD) resistance, the G2576U mutation in the 50S ribosomal subunit. The cfr-gene mediates a novel LZD-R mechanism via methylation of nucleotide A2503, in the vicinity of the peptidyl transferase center of the 50S. This methylation renders ribosomes not only LZD-R, but also resistant to unrelated antibiotic classes, such as phenicols, lincosamides, pleuromutilins, and streptogramins all interacting with the ribosome near base A2503. Methods: Escherichia coli(RS676, tolC -), has a single copy of 23S rRNA and was transformed with plasmid (pBgIII), encoding the cfrgene. Functional cfr-methylase was confirmed by MIC testing. IC50s of RZD, torezolid (TR-700) and LZD were determined using in vitrotranslation assays with cfr-methylated ribosomes. The X-ray structure of RZD bound to 50S was determined and together with the LZD structure (previously reported) used to generate a comparative residue by residue analysis of drug-ribosome interactions, carried out using MCPRO. Results: The IC50s for RDZ, TR-700 and LZD vs. cfr-methylated ribosomes were 0.26, 0.77 and 13 µM, respectively. The differences in IC50s were reflected in the in vitropotency as tested by MICs vs. E. coli(RS676, tolC -, cfr) with MICs of 2, 8 and 128 µg/ml, respectively. The residue by residue analysis for the interactions of RDZ and LNZ with nucleotides U2584, U2585 & A2602, away from the resistant site, show a substantial ΔE difference: -11.4 (RDZ) vs. -1.2 (LZD) kcal mol-1. Conclusions: Analysis of RDZ and LZD bound to the 50S subunit offers a rational explanation for the higher affinity of RDZ vs. LZD. The increased affinity of RDZ is due to ribosome-RDZ interactions that are far from, and not affected by ribosomal mutations/modifications linked to LZD-R, including cfr-mediated A2503 methylation.
- Добавил в систему: Скрипкин Евгений Алексеевич