Clinical implications of macrolide resistance in community-acquired respiratory tract infections.

Laboratory surveillance data suggest that macrolide resistance among Streptococcus pneumoniae has increased dramatically over the past 15 years. This review examines the specifics of macrolide resistance and the clinical relevance of in vitro susceptibility testing in light of the pharmacokinetics and pharmacodynamics of azithromycin and clarithromycin. These drugs concentrate extensively within respiratory tissue and have other positive characteristics not reflected by in vitro susceptibility testing. In general, clarithromycin is the most potent macrolide and the one most likely to maintain clinical efficacy against the low-level resistance associated with most macrolide-resistant pneumococci in the USA. These findings suggest that susceptibility data may underestimate clinical utility and that clarithromycin still has a place in the empiric treatment of respiratory infections.