ERYTHROMYCIN AND AZITHROMYCIN TRANSPORT INTO HAEMOPHILUS-INFLUENZAE ATCC-19418 UNDER CONDITIONS OF DEPRESSED PROTON MOTIVE FORCE (DELTA-MU-H)

The effect of collapsing the electrochemical proton gradient (ΔμH) and [3H]erythromycin and [14C]azithromycin transport in Haemophilus influenzae ATCC 19418 was studied. The proton gradient and membrane potential were determined from the distribution of [2-14C]dimethadione and rubidium-86, respectively. ΔμH was reduced from 124 to 3 mV in EDTA-valinomycin-treated cells at 22°C with 150 mM KCI and 0.1 mM carbonyl cyanide m-chlorophenylhydrazone. During the collapse of ΔμH, macrolide uptake increased. Erythromycin efflux studies strongly suggested that this increase was not due to an energy-dependent efflux pump but was likely due to increased outer membrane permeability. These data indicated that macrolide entry was not a ΔμH-drive active transport process but rather a passive diffusion process.