Kill kinetics of antimicrobial agents against Helicobacter pylori.

We evaluated the activity of clarithromycin, 14-OH clarithromycin, amoxycillin, bismuth, metronidazole and ciprofloxacin against six strains of Helicobacter pylori to determine if there were differences in response to these antimicrobial agents during growth in vitro. Clarithromycin and its 14-hydroxy-metabolite exhibited an early bactericidal activity with at least a 3 log10 reduction after 2-8 incubation. Exposure to bismuth, ciprofloxacin and metronidazole resulted in a > 3 log reduction by 24 h with the greatest decrease in viability occurring between 8 and 24 h. The viable count of three strains was reduced by a 1-2 log10 after 24 h exposure to amoxycillin and by a > 3 log10 after 48 h.