A large cross-sectional study to investigate the prevalence and possible modes of transmission of Helicobacter pylori was done in southern China. Serum samples (1727) were collected from Guangzhou city and three rural areas of Guangdong Province, and the prevalence of H. pylori infection was determined using an ELISA. Each subject completed a questionnaire. The overall prevalence of H. pylori infection was 44.2%; a significantly higher prevalence was found in Guangzhou (52.4%) than in the rural areas (38.6%). This difference was generally reflected in the group 0-5 years old, but the rate of increase in seroprevalence for H. pylori over 5 years of age was similar (1%/year). This study provides important new data on the acquisition of H. pylori, particularly in the early years of life, and shows that density of living conditions is a prime determinant in the acquisition of H. pylori.

Stomach biopsy specimens from greater than 40 individuals with Campylobacter pyloridis-associated gastritis were examined by light and electron microscopy. The bacteria were consistently seen in two locations: within the gastric mucus and associated with intercellular junctions of gastric epithelial cells. C. pyloridis is suggested to be one of a broad group of spiral bacteria that are adapted to the peculiar niche provided by intestinal mucus. The spiral morphology and the form of motility of these organisms give them a selective advantage in a viscous environment. This point has been demonstrated in vitro by measurement of the velocity of clinical isolates in solutions of methyl cellulose of varying viscosity. The localization of C. pyloridis close to intercellular junctions is proposed to be due to the presence of preferred metabolites or growth factors, e.g., urea and hemin. All isolates show an extremely high urease activity and require hemin for growth.

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Helicobacter pylori strain diversity was investigated in infected persons by collection of multiple biopsies before and after therapy failure. It was demonstrated by random amplification of polymorphic DNA polymerase chain reaction that patients may be infected with a mixed population of H. pylori strains. Most patients were colonized with a predominant strain accompanied by up to 5 variant strains. The use of antimicrobials resulted in an altered distribution of the strains present, but the predominant strain usually remained. Patients may be infected with a mixed population of metronidazole-sensitive and -resistant strains at one time, with metronidazole-based therapy selectively enriching for a resistant population.