Erythromycin-resistant viridans streptococci are often responsible of bacteremias following dental manipulations. The aim of this study was to evaluate the in vitro activity of telithromycin against erythromycin-susceptible and erythromycin-resistant viridans streptococci. Venous blood samples were collected from 84 patients, 30 s after dental extractions. Viridans streptococci were identified by conventional microbiological techniques. A set of 36 viridans streptococci were selected to investigate the in vitro activity of telithromycin by the agar dilution method. Macrolide resistance genes were amplified with specific primers for the mefA and ermB genes and visualized by electrophoresis. For erythromycin-susceptible viridans streptococci, telithromycin minimal inhibitory concentration90 (MIC90) was <0.008 microg/ml. For erythromycin-resistant viridans streptococci, telithromycin MIC90 was 1 microg/ml. The MIC90 to telithromycin of the mefA-positive and ermB-negative viridans streptococci was lower than that of the mefA-negative and ermB-positive viridans streptococci (0.128 microg/ml versus 1 microg/ml). The in vitro activity of telithromycin was high, irrespective of the erythromycin susceptibility and the mechanism of erythromycin resistance identified.
Copyright (c) Blackwell Munksgaard, 2005