[Molecular analytical evaluation of macrolide- and ketolide-resistant Streptococcus pneumoniae--mechanism of action of telithromycin and resistance to it]

Abstract

PROTEKT (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin) is a worldwide epidemiologic survey for investigating drug susceptibility against major bacterial pathogens in respiratory tract infections, and that is also designed to identify the action mechanism of telithromycin (TEL), a ketolide antibacterial agent, on the resistant Streptococcus pneumoniae and the resistance mechanism for TEL on the TEL-resistant S. pneumoniae strain, in addition to determine macrolide/ketolide resistant S. pneumoniae activities of TEL using molecular analysis. TEL exerted the antibacterial action on the macrolide-resistant S. pneumoniae regardless maintaining the macrolide-resistant mechanism and exhibited the potent antibacterial activity against all of ermB gene-positive strains, mefA gene-positive strains and ribosome variants. This result was considered to reflect the fact that TEL did not induce resistance to ermB and had extremely low ability to select resistant strain by mutation. These actions of TEL were considered to be derived from its novel chemical structure and might be characteristics of ketolides not possessed by macrolides. In the survey of PROTEKT in 1999 to 2002, among 13,864 strains of S. pneumoniae isolated worldwide, ketolide-resistant strain (TEL MIC > or = 4 microg/ml) was observed in 10 strains (0.07%). MIC of these 10 strains was 4 or 8 microg/mL and all of these strains were ermB-positive strains. Based on this fact, potential involvement of adenine demethylase (ermB gene product) was considered in the background of development of ketolide-resistant S. pneumoniae.