Influence of anti-Helicobacter triple-therapy with metronidazole, omeprazole and clarithromycin on intestinal microflora

Background: Proton pump inhibitor-based therapy including two antibiotics is the treatment of choice for Helicobacter pylori infection. Oral antibiotic treatment can lead to intestinal overgrowth of potentially pathogenic bacteria, Aim: To investigate the intestinal microflora before and at different times after H. pylori treatment with omeprazole, clarithromycin and metronidazole. Methods: Bacterial growth in faecal samples from 51 patients infected with H. pylori was determined qualitatively and quantitatively. During the same period of time, stool samples from 27 H. pylori-negative controls were taken and investigated at the same intervals. Results: The microflora of H. pylori-infected patients was different from that in H. pylori negative controls. It was characterized by a high concentration of lactobacilli, mainly Lactobacillus acidophilus. Immediately after therapy there was an increased colonization with yeasts, while the growth of lactobacilli and other species was inhibited. Clostridium difficile was cultured from three cases, but without clinical manifestations of pseudomembranous colitis. After 4 weeks of therapy, the microflora returned to normal and was not different from that of the H. pylori-negative control group. Conclusions: In H. pylori-positive patients the intestinal flora is characterized by an increase in growth of acid-tolerant L. acidophilus. Eradication therapy exerts only a short-term influence on intestinal flora, whereas in the long term, the intestinal microflora is restored to a pattern similar to that of the control group.