Antibiotic susceptibility of attached and free-floating Helicobacter pylori

Helicobacter pylori are found attached to mucous cells of the human stomach or under the mucous layer. Models mimicking the in vivo situation may be more suitable for H. pylori MIC determinations than traditional agar dilution methods. Megraud et al. (Antimicrobial Agents and Chemotherapy 1991, 35, 869-72) developed a model for measuring the susceptibility of attached and free-floating H. pylori. We have modified this model so that free-floating and attached H. pylori are treated in a more similar manner, before and after incubation with antibiotic, and performed additional controls to ensure H. pylori and tissue culture cells are not detrimentally affected and maintain their viability during the course of the experiment. We found only 10% of plate-grown H. pylori were competent for attachment to HEp-2 cells; however, all progeny of attached bacteria remained adherent. Killing curves were performed using 0, 0.001, 0.01, 0.1 and 1 mg/L amoxycillin, and 0, 0.0025, 0.0075 and 0.01 mg/L clarithromycin. H. pylori divided at concentrations