Association between Helicobacter pylori genotypes and gastric disorders in relation to the cag pathogenicity island

Helicobacter pylori is a bacterium associated with upper gastrointestinal diseases in humans. However, only a small proportion of infected people become sick. Although several studies have tried to establish an association between known virulence markers and clinical outcomes, in many cases the results have been conflicting. The aim of this study was to investigate the importance of virulence markers to predict clinical outcome in Brazil. Mixed infections by genetically unrelated strains detected by vacA genotyping were found in 18% of the patients. The cagA and cagE genes and the vacAsl genotype were associated with the development of peptic ulcer disease (PUD). The cagAvacAslml genotype was associated with PUD and duodenal ulcer (DU). Conversely, jhp947 was not associated with DU or PUD, indicating that this gene is not a universal virulence marker. These results also show that a high proportion of the patients were simultaneously infected by cag-positive and cag-negative H. pylori types. This finding suggests the existence of a dynamic equilibrium between the loss and gain of the cag pathogenicity island, probably depending on the physiologic conditions of the patient's stomach. To the best of our knowledge, this is the first study that has documented this finding in Brazil. (c) 2007 Elsevier Inc. All rights reserved.