Adnan Al-Lahham1, Ralf René Reinert. 1. Institute of Medical Microbiology, National Reference Centre for Streptococci, Aachen, Germany.
Abstract
BACKGROUND: Telithromycin is a new ketolide increasingly used in Europe and the United States. Only very few telithromycin-resistant isolates have been described to date. METHODS: The anti-pneumococcal activity of telithromycin was determined against four clinical isolates of Streptococcus pneumoniae with reduced susceptibility to telithromycin by time-kill methodology. RESULTS: All four telithromycin non-susceptible strains had the constitutive macrolide-lincosamide-streptogramin B phenotype and the ermB genotype. Pneumococcal strains had telithromycin minimum inhibitory concentrations (MICs) ranging between 2 and 8 microg/ml. Mulitlocus sequence typing and serotyping showed three isolates to harbour the identical serotype (serotype 14) and sequence type (sequence type 143) indicating a genetic relatedness of strains. Telithromycin was only bactericidal against the isolates with telithromycin resistance, with 4-8 times the MIC after 24 h. CONCLUSION: The killing by telithromycin of S. pneumoniae isolates having an ermB resistance determinant and a telithromycin MIC of > or =2 microg/ml is slow. Achievable concentrations in serum, alveolar macrophages and epithelial lining fluid are below the concentrations which are necessary for bactericidal killing of highly telithromycin-resistant strains. Copyright 2007 S. Karger AG, Basel.
BACKGROUND:Telithromycin is a new ketolide increasingly used in Europe and the United States. Only very few telithromycin-resistant isolates have been described to date. METHODS: The anti-pneumococcal activity of telithromycin was determined against four clinical isolates of Streptococcus pneumoniae with reduced susceptibility to telithromycin by time-kill methodology. RESULTS: All four telithromycin non-susceptible strains had the constitutive macrolide-lincosamide-streptogramin B phenotype and the ermB genotype. Pneumococcal strains had telithromycin minimum inhibitory concentrations (MICs) ranging between 2 and 8 microg/ml. Mulitlocus sequence typing and serotyping showed three isolates to harbour the identical serotype (serotype 14) and sequence type (sequence type 143) indicating a genetic relatedness of strains. Telithromycin was only bactericidal against the isolates with telithromycin resistance, with 4-8 times the MIC after 24 h. CONCLUSION: The killing by telithromycin of S. pneumoniae isolates having an ermB resistance determinant and a telithromycin MIC of > or =2 microg/ml is slow. Achievable concentrations in serum, alveolar macrophages and epithelial lining fluid are below the concentrations which are necessary for bactericidal killing of highly telithromycin-resistant strains. Copyright 2007 S. Karger AG, Basel.