DNA typing for Helicobacter pylori isolates from eradication-failed patients: comparison of the isolates before and after therapy T. NADA*, T. ANDO  , K. NOBATA  , T. TSUZUKI  , M. MINAMI  §, K. INA  , Y. IINUMA à , S. ICHIYAMA à , M. OHTA§, E. EL-OMAR – , K. KUSUGAMI  & H. GOTO   *Department of Clinical Laboratory, Nagoya University Hospital, Nagoya; Departments of  Therapeutic Medicine and §Bacteriology, Nagoya University Graduate School of Medicine, Nagoya; àDepartment of Laboratory Medicine and Infectious Diseases, Kyoto University Graduate School of Medicine, Kyoto, Japan; and –Department of Medicine and Therapeutics, University of Aberdeen, Aberdeen, UK SUMMARY Background: Failure of Helicobacter pylori eradication occurs frequently despite use of multiple microbial agents. Aim: We aimed to study differences between H. pylori strains isolated before and after eradication failure. Methods: We treated 87 patients with peptic ulcer using triple therapy consisting of omeprazole plus combina- tions of clarithromycin, amoxicillin, or metronidazole. We studied the status of cagA, vacA, and iceA by PCR, and examined the differences in H. pylori isolates by pulsed-field gel electrophoresis and arbitrary primer polymerase chain reaction. The minimum inhibitory concentration of clarithromycin, amoxicillin, or met- ronidazole was determined by an agar dilution method. Results: Eradication therapy failed in 12 patients (14%); H. pylori isolates were obtained from all of these both before and after therapy. After eradication therapy, 10 patients were colonized with the same strain as before therapy, while the other two patients were colonized with different strains from those before therapy. In the former group, one isolate changed from metronidazole-sensitive to -resistant, one changed from clarithromycin- and metronidazole-sensitive to -resistant, and four were resist- ant to clarithromycin or metronidazole both before and after therapy. The other four isolates remained sensitive to clarithromycin and metronidazole after therapy. In the two patients who yielded apparently different isolates after therapy, they changed from clarithromycin- and metroni- dazole-sensitive to -resistant. Conclusion: Eradication of H. pylori by first-line therapy is an important goal in the treatment of H. pylori- positive peptic ulcer, and that appropriate antimicrobial sensitivity testing should be conducted in patients with eradication failure. I NTRODUCTION Helicobacter pylori, a microaerophilic Gram-negative bacterium that colonizes the human stomach, was first isolated from gastric biopsies by Warren and Marshall in 1983. 1 H. pylori is speculated to be involved in the pathogenesis of chronic active gastritis, duodenal ulcer, gastric ulcer and gastric cancer. 2, 3 It is known that eradication of H. pylori leads to significant improvements in both acute and chronic inflammatory responses in the gastric mucosa. 4 Eradication of H. pylori improves associated gastric inflammatory changes and markedly reduces the recurrence of gastric and duo- denal ulcers. 4–7 Combination triple therapy, consisting of a proton pump inhibitor, amoxicillin (amoxicillin C), and clarithromycin or metronidazole is commonly recom- mended for eradication of H. pylori. 8 In recent years, however, the development of H. pylori resistance to antimicrobial drugs has become an important clinical Correspondence to: Dr T. Ando, Department of Therapeutic Medicine, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa- ku, Nagoya, 466-8550, Japan. E-mail: takafumia-gi@umin.ac.jp Aliment Pharmacol Ther 2004; 20 (Suppl. 1): 39–47. Ó 2004 Blackwell Publishing Ltd 39