Microbial ecology and treatment of Helicobacter pylori infections: Review

The aims of the present study were to investigate the ecological disturbanc es caused by four different anti-H. pylori regimens, to compare different m ethods for diagnosing H. pylori, and to study the genetic variability of H. pylori. The patients included in the study were all treated at the Center of Gastro enterology, Huddinge University Hospital, Karolinska Institute. All patient s were H. pylori-positive before entering the study, confirmed by rapid ure ase test, histology, culture and urea breath test or PCR. Treatment regimen s included in the study were omeprazole alone (OP), in combination with amo xicillin (OA), in combination with amoxicillin and metronidazole (OAM) and in combination with clarithromycin and metronidazole (OCM). Samples from th e mouth (saliva and dental plaque), stomach (biopsies from the gastric muco sa in the corpus and in the antrum) and the intestine (feces) were collecte d before, during and after treatment. The oral microflora was challenged by the three treatment regimens including antimicrobial agents, with the emer gence of resistant streptococci and staphylococci in the OCM group. Bacteri al strains in the gastric mucosa increased in numbers during treatment in a ll treatment groups, probably due to the pH rise, which provides a better e nvironment for the commensal microflora. This overgrowth was especially pro nounced during treatment with omeprazole alone (OP), possibly due to the fa ct that a concomitant suppression exerted by the antimicrobial agents occur red in the other treatment groups. H. pylori was, on the other hand, suppre ssed during treatment in all treatment groups, possibly due to a direct eff ect of omeprazole and to the colonization resistance expressed by the norma l microflora, An emergence of resistant commensal strains in the gastric mu cosa was seen in the OCM and the OAM groups. The intestinal microflora was most altered in the OAM and the OCM groups, with persistent disturbances in the OCM group 4 weeks after treatment. The frequency of resistant Enteroco ccus spp, (OCM), Enterobacteriaceae spp, (OA and OAM) and Bacteroides spp, (OCM) was increased during and after treatment. Different detection methods for H. pylori were compared and PCR was shown t o have higher sensitivity than other routine diagnostic tests. The patients in the present study seemed to be colonized with a single stra in of H. pylori. Treatment failures in patients treated with OAM were cause d by recrudescence. These four patients with relapsing H. pylori infection, were shown to be reinfected with the original H. pylori strain, indicating that H. pylori escapes treatment by a thus far unknown mechanism.