Microbiological profile of telithromycin, thee first ketolide antimicrobial

Telithromycin, the first of the ketolide antimicrobials, has been specifica lly designed to provide potent activity against common and atypical/intrace llular or cell-associated respiratory pahtogens, including those that are r esistant to beta -lactams and/or macrolide-lincosamide-streptogramin(B) (ML SB) antimicrobials. Against Gram-positive cocci, telithromycin possesses mo re potent activity in vitro and in vivo than the macrolides clarithromycin and azithromycin. It retains its activity against erm-(MLSB) or mef-mediate d macrolide-resistant Streptococcus pneumoniae and Streptococcus pyogenes a nd against Staphylococcus aureus resistant to macrolides through inducible MLSB mechanisms. Telithromycin also possesses high activity against the Gra m-negative pathogens Haemophilus influenzae and Moraxella catarrhalis, rega rdless of beta -lactamase production. In vitro, it shows similar activity t o azithromycin against H. influenzae, while in vivo its activity against H. influenzae is higher than that of azithromycin. Telithromycin's spectrum o f activity also extends to the atypical, intracellular and cell-associated pathogens Legionella pneumophila, Mycoplasma pneumoniae and Chlamydia pneum oniae. In vitro, telithromycin does not induce MLSB resistance and it shows low potential to select for resistance or cross-resistance to other antimi crobials. These characteristics indicate that telithromycin will have an im portant clinical role in the empirical treatment of community-acquired resp iratory tract infections.