Abstract
The antibacterial activities of telithromycin (TEL), azithromycin, clarithromycin, roxithromycin, levofloxacin (LVFX), ampicillin (ABPC) and erythromycin (EM) were determined against 140 strains of oral streptococci, the major pathogens in dental infbctions. Atthesame time, the antibacterial activities of ketolide-antibiotics were tested against experimentally induced strains that werehighly resistant to macrolides. In the EM-resistant strains, the presence of erm and mef genes was investigated. The MIC90 of each of the fbur 14-or 15-member ring macrolide antibiotics was high against Streptcoccus mitis in the viridans group (1 to 8μg/mL); howeverthe MIC of TEL wasbelow 0.5μg/mL, which was sufficient to inhibit the growth of all the organisms. TEL also did not exhibit cross resistance with macrolides, and displayed the most outstanding antibacterial activity among the test agents, including ABPC and LVFX. No changes were noted in Streptococcus intermedius befbre and after clarithromycin (CAM) resistance induction. After resistance induction, the MIC of CAM against S. mitis rose 16 times. Against two strains of Streptococcus oralis, the MIC of CAM rose to 16 and 256, respectively, after resistance induction. The MIC of TEL rose only slightly (from 0.03 to 0.12μg/mL) against the strains into which CAM resistance had been induced. TEL did not exhibit cross resistance with 14-or 15-member ring macrolides in ermB or mefA gene Carrying Strains.
