Antimicrobial Activities and Postantibiotic Effects of Clarithromycin, 14-Hydroxy-Clarithromycin, and Azithromycin in Epithelial Cell Lining Fluid against Clinical Isolates of<i>Haemophilus influenzae</i>and<i>Streptococcus pneumoniae</i>

Abstract

The antimicrobial activity of concentrations of selected macrolides found in epithelial cell lining fluid was investigated. Clarithromycin demonstrated greater potency and a significantly longer postantibiotic effect (PAE) than azithromycin against Streptococcus pneumoniae. Azithromycin displayed greater potency, faster killing, and a longer PAE than clarithromycin against Haemophilus influenzae. Drug concentrations in epithelial cell lining fluid similar to those found in tissue did not improve the synergistic potential of 14-hydroxy-clarithromycin and indicate that a maximal PAE may exist despite increasing concentrations of drug.