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

Omeprazole 20 mg once (o.d.) or twice daily (b.d.), clarithromycin 250 mg b.d., and tinidazole 500 mg b.d. 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 (Mast Diagnostics, Bootle, UK) and E-test (Cambridge Diagnostics Services, Cambridge, UK) 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 the measurement of minimum inhibitory concentration (MIC) using the E-test. One hundred and forty-one H. pylori-infected patients were enrolled in the study and the organism was successfully cultured from 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 μg/ml to define metronidazole resistance eradication rates were higher against sensitive (9/12; 75%) than 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.