Relevance of antibiotic sensitivities in predicting failure of omeprazole, clarithromycin, and tinidazole to eradicate Helicobacter pylori.

Omeprazole 20mg once (od) or twice daily (bd), clarithromycin 250mg bd, and tinidazole 500 mg bd for 7 days (OCT) is an effective regimen against Helicobacter pylori, but the effect of 5-nitroimidazole resistance is unclear. We aimed to evaluate this using the disc diffusion technique and E-test to assess 5-nitroimidazole resistance. H. pylori was cultured from antral biopsies of infected patients as determined by 13C-urea breath test (13C-UBT), histology, and/or rapid urease test. Patients were prescribed OCT, and H. pylori eradication was assessed by 13C-UBT at least 4 weeks after completion of therapy. Antibiotic sensitivities to metronidazole and clarithromycin were evaluated by the disc diffusion method and by minimum inhibitory concentration (MIC) using the E-test. One hundred and forty-one H. pylori-infected patients were enrolled into the study and the organism was successfully cultured in 119 patients (84%). The overall eradication rate was 125/141 (89%). OCT was successful in 62/69 (90%) patients harboring fully sensitive strains of H. pylori compared with 42/45 (93%) of patients with strains that were resistant to metronidazole alone (P = 0.74, Fisher's exact test). MIC was assessed in 22 samples. Using a cut-off point of > 32 microg/ml to define metronidazole resistance, eradication rates were higher against sensitive (9/12; 75%) compared with resistant (3/10; 30%) strains (P = 0.08, Fisher's exact test). 5-Nitroimidazole resistance assessed by the disc diffusion technique is not helpful in predicting OCT failure, but the E-test may be of value.