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 250 mg bd, an d tinidazole 500 mg bd for 7 days (OCT) is an effective regimen against Hel icobacter 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 bio psies of infected patients as determined by C-13-urea breath test (C-13-UBT ), histology, and/or rapid urease test. Patients were prescribed OCT, and H . pylori eradication was assessed by C-13-UBT at least 4 weeks after comple tion of therapy. Antibiotic sensitivities to metronidazole and clarithromyc in were evaluated by the disc diffusion method and by minimum inhibitory co ncentration (MIC) using the E-test. One hundred and forty-one H. pylori-inf ected patients were enrolled into the study and the organism was successful ly cultured in 119 patients (84%). The overall eradication rate was 125/141 (89%). OCT was successful in 62/69 (90%) patients harboring fully sensitiv e strains of H. pylori compared with 42/45 (93%) of patients with strains t hat 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 mu g/ml to de fine metronidazole resistance, eradication rates were higher against sensit ive (9/12; 75%) compared with resistant (3/10; 30%) strains (P = 0.08, Fish er's exact test). 5-Nitroimidazole resistance assessed by the disc diffusio n technique is not helpful in predicting OCT failure, but the E-test may be of value.