The bactericidal activity of magainins againstPseudomonas aeruginosaandEnterococcus faecium

摘要

The antimicrobial activities of two synthetic magainins, MSI 94 and MSI 93, were investigatedin vitroagainst 20 clinical isolates each ofPseudomonas aeruginosaandEnterococcus faecium. The ranges of the MICs of both agents were 6·25–50 mg/L forP. aeruginosaand 3·13–12·5 mg/L forE.faeciun. In time-kill studies, the magainins demonstrated rapid, concentration-dependent bactericidal activity against selected isolates of both species. This bactericidal effect was inoculum-dependent forP. aeruginosain both the logarithmic and stationary phases of growth. Bacterial regrowth was regularly observed after 24 h of incubation in the time-kill studies; this was due to loss of antimicrobial activity during overnight incubation rather than to the development of resistance. More rapid and sustained bactericidal activity was noted when the magairuns were combined with either silver nitrate (AgNO3) or gentamicin againstP. aeruginosaand with gentamicin againstE. faecium. Neither agent produced a post-antibiotic effect onP. aeru