title: Ribosome affinity and the prolonged molecular postantibiotic effect of cethromycin (ABT-773) in Haemophilus influenzae.
abstract: Cethromycin (ABT-773) is a new ketolide currently in clinical trials, for treatment of community acquired respiratory tract infections. The drug is active in vitro and in vivo against Haemophilus influenzae. In this study, the mechanism of action of cethromycin was investigated in H. influenzae. The drug effect was studied using in vitro transcription-translation and whole cell amino acid incorporation. Both cethromycin and erythromycin inhibit protein synthesis with similar potencies; cethromycin, however, had a prolonged molecular postantibiotic effect (PAE) compared with erythromycin which was consistent with previously reported microbiological data. Ribosome binding assay using ribosomes isolated from H. influenzae NP200 revealed that the ribosome binding affinity of cethromycin was more than 20-fold tighter than that of erythromycin. Studies of binding kinetics showed that the tight binding of cethromycin mainly contributed to the 20-fold slower dissociation from cells. Further studies showed cethromycin had a four-fold faster drug accumulation rate than erythromycin. Therefore, the tight binding of cethromycin with ribosomes likely contributed to the faster drug accumulation, slower dissociation from cells and prolonged molecular PAE of cethromycin for H. influenzae.
authors.affiliation: Dept. R42A, Infectious Disease Research, Bldg. AP30, Abbott Laboratories, 200 Abbott Park Road, Abbott Park, IL 60064-6145, USA.
authors.forename: Zhensheng
authors.initials: Z
authors.lastname: Cao
authors.forename: Ping
authors.initials: P
authors.lastname: Zhong
authors.forename: Xiaoan
authors.initials: X
authors.lastname: Ruan
authors.forename: Phil
authors.initials: P
authors.lastname: Merta
authors.forename: John O
authors.initials: JO
authors.lastname: Capobianco
authors.forename: Robert K
authors.initials: RK
authors.lastname: Flamm
authors.forename: Angela M
authors.initials: AM
authors.lastname: Nilius
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004917:Erythromycin / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D006193:Haemophilus influenzae / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D048628:Ketolides / Q000494:pharmacology*; D014176:Protein Biosynthesis / Q000187:drug effects; D012338:RNA, Ribosomal, 23S / Q000187:drug effects / Q000235:genetics; D012270:Ribosomes / Q000187:drug effects / Q000502:physiology*; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D048628:Ketolides; D012338:RNA, Ribosomal, 23S; D004917:Erythromycin; C405499:cethromycin