In vitro activity of clarithromycin against intracellular Helicobacter pylori

The in vitro intracellular effect of clarithromycin, amoxicillin, metronida zole, lansoprazole, and rifabutin, tested at concentrations corresponding t o one times the MIG, two times the MIG, and four times the MIG, was evaluat ed against an invasive Helicobacter pylori strain. At four times the MIG, c larithromycin showed an early bactericidal effect within 4 h of incubation and, in determining the complete killing within a 16 h-incubation period, l ansoprazole and rifabutin showed comparable activity, yielding bactericidal activities within 4 and 8 h of incubation, respectively. Amoxicillin and m etronidazole showed bacteriostatic activity only.