Antimicrobial resistance in isolates of Helicobacter pylori in a referral center.

Objective. To estimate the frequency of H. pylori clinical isolates resistant to six commonly used antimicrobials. Design. Cross-sectional observational study. Setting. A tertiary-referral health care institution in Mexico City. Participants. 31 isolates of H. pylori from 31 patients with chronic antral gastritis were obtained from gastric mucosal biopsy specimens. Main outcome measure. The Minimum Inhibitory Concentration (MIC) to ampicillin, amoxycillin, tetracycline, doxycycline, metronidazole and to colloidal bismuth subcitrate was determined by the agar plate dilution test. Results. All isolates showed to be susceptible to the former four antibiotics but only in 46% and 55% growth was inhibited by 8 mu g/mL and 16 mu g/mL of metronidazole, respectively. All isolates were inhibited by less than or equal to 128 mu g/mL of bismuth. A 50% increase in the percentage of metronidazole-resistant isolates (MIC greater than or equal to mu g/mL) between 1988 to 1992 was observed. Conclusion. There is a need of future studies in our setting aimed at assessing the cost/effectiveness of diverse H. pylori-associated peptic ulcer treatment options.