Use of time-kill methodology to assess antimicrobial combinations against metronidazole-susceptible and metronidazole-resistant strains of Helicobacter pylori.

Optimal therapy for Helicobacter pylori infection to date, consists of metronidazole, bismuth, and tetracycline. This combination, however, is less effective against metronidazole-resistant organisms. We used a time-kill kinetic methodology to assess the bactericidal effects of selected agents, alone and in combination, to a metronidazole-susceptible and a metronidazole-resistant strain of H. pylori. single, double, and triple agents showed increasing bactericidal activity. The combination of metronidazole, bismuth, and tetracycline showed maximal killing effect (no detectable regrowth) against the susceptible strain, but against the resistant strain this combination showed less killing. The time-kill methodology may therefore offer an in vitro approach to the initial selection of agents to be evaluated for the treatment of H. pylori infections.