Novel real-time PCR assay for detection of Helicobacter pylori infection and simultaneous clarithromycin susceptibility testing of stool and biopsy specimens.

A biprobe real-time PCR protocol, followed by hybridization melting point analysis, to detect point mutations in the 23S rRNA gene of Helicobacter pylori associated with clarithromycin resistance was established and evaluated in a clinical study. Of 92 patients who underwent endoscopy, 45 were found to be H. pylori infected and invariably were also culture positive. Of the 45 isolates, 11 were shown to be resistant to clarithromycin by E-test. With respect to the detection of H. pylori infection, PCR showed sensitivities of 100% in biopsies and 98% in stool specimens and a specificity of 98% in both biopsy and stool samples. All clarithromycin-sensitive cases were identified as such by PCR in both biopsy and stool samples. Of the cases with a resistant strain, eight were identified as such in stool DNA and nine were identified in biopsy DNA. Failure of PCR to detect the resistant genotype in the biopsy DNA, stool DNA, or both (one case) was associated with mixed populations. In these cases, patients had not been treated for H. pylori infection before, and the sensitive population showed to be present in considerably higher numbers than the resistant population. In five of six cases in which infection with a resistant genotype only was identified by PCR, the patients had received clarithromycin-based eradication therapy in the past. Thus, the assay presented provides a highly accurate noninvasive method to detect H. pylori infection in stool and at the same time allows for culture-independent clarithromycin susceptibility testing.

Helicobacter pylori and gastric malignancies.

Clinical outcomes of Helicobacter pylori infection are diverse and caused by the variability of H. pylori virulence factors, host susceptibility, environmental factors and their interactions. Prospective epidemiological studies have clearly shown the relationship between H. pylori infection and gastric cancer. In addition, studies in animal models such as Mongolian gerbils with or without the addition of low-dose chemical carcinogens demonstrated that H. pylori infection can develop gastric carcinoma. Experimental studies have shown that virulence factors of H. pylori interact with gastric epithelial cell signaling related to carcinogenesis. While the effect of H. pylori eradication on prevention of such tumors in chronic H. pylori carriers is still controversial, progress has been made in therapy especially of gastric lymphoma with well tolerated chemotherapeutic regimen.

Comparison of spiral-computed tomography with water-filling of the stomach and endosonography for gastric lymphoma of mucosa-associated lymphoid tissue-type.

BACKGROUND: Endosonography has been reported as the method of choice for local staging of patients with gastric lymphoma of mucosa-associated lymphoid tissue (MALT)-type. As endosonography is still restricted to specialized centers, we have investigated the use of spiral computed tomography of the abdomen with water-filling of the stomach (hydro-spiral CT) for enhanced contrast in patients with gastric lymphoma. PATIENTS AND METHODS: Patients with a histological verified diagnosis of gastric lymphoma of MALT-type were included in this prospective series. All patients underwent routine staging procedures including endosonography of the upper GI-tract carried out by a single individual. In addition, patients were subjected to hydro-spiral CT either before or after endosonography within a maximal time span of 4 weeks. Results of hydro-spiral CT were compared to those of the endosonographic evaluation and histological work-up of biopsy specimens. RESULTS: A total of 14 patients with primary gastric lymphoma of MALT-type (3 with a high-grade component) were studied prospectively. All patients underwent hydro-spiral CT before initiation of treatment, and 2 patients were also studied following chemotherapy. In the pretherapeutic setting, hydro-spiral CT identified gastric lymphoma in 8 patients, while a false negative result was seen in 6 patients. In addition, the localization of the lymphoma within the stomach was divergent between CT and endosonography in 1 patient. In the 2 patients who were also studied after therapy, CT showed unchanged thickening of the stomach wall in spite of normalization in the endosonographic assessment as well as the histologic evaluation. CONCLUSION: Our results demonstrate the superiority of endosonography over hydro-spiral CT for the staging and follow-up of patients with gastric lymphoma, who should therefore be managed at centers where endosonography is available.

[Significance of Helicobacter pylori infection for stomach lymphoma and stomach carcinoma]. / Bedeutung der Helicobacter pylori-Infektion für Magenlymphom und Magenkarzinom.

The discovery of Helicobacter pylori in 1983 revolutionised pathogenetic hypotheses of almost all gastric diseases and markedly enhanced research especially in the field of malignant tumours of this organ. Based on epidemiological studies indicating an association of H. pylori infection and malignant gastric tumours the WHO classified this bacterium as "class I carcinogen" already in 1994. Although the high prevalence of this germ worldwide is sharply contrasting the low incidence of gastric carcinomas and lymphomas its role as independent risk factor in the carcinogenesis of these tumours today is reasonably evidence-based. Thus, epidemiologists are calculating a reduction of 80% of all MALT-type lymphomas and of about 60% of gastric "non cardia" carcinomas in the scenario of an "H. pylori-free" world. However, complete remission of 80% of early lymphomas of MALT-type confined to mucosa and submucosa, only, after antibiotic eradication of the bacterium is well established in literature and follow-up data are confirming sustained response after years. The strength of impact of an H. pylori infection on gastric carcinogenesis will be figured out by prospective studies on a non infected population in the future.