Helicobacter pylori is not considered a commensal organism. Infection in humans is always associated with some degree of inflammatory response by the body and pathology. However, the exact role of H. pylori infection in the development of duodenal or gastric ulcer disease remains unclear.

• Infected people may suffer hypergastrinemia, which could contribute to increased parietal cell activity and gastric acidity.
• Infection may induce inflammatory cytokines, such as TNF, IL-1 or IL-6, or tissue damaging superoxides.
• Pathogenicity may be related to translocation of the CagA protein of H. pylori into gastric epithelial cells, and its subsequent phosphorylation on tyrosine.

Most experts feel that H. pylori infection alone is not sufficient to induce ulcers. However, the recurrence rate of ulcerative disease is much lower if the infection is treated with antibiotics, rather than simply treating the ulcer itself symptomatically. Infections in humans are typically treated with a combination of three drugs, metronidazole, tetracycline and bismuth subsalicylate, for 2-3 weeks. This regime is reported to produce an 86% infection cure rate.

• Interestingly, however, there is a high rate of resistance to metronidazole and clarithromycin among H. pylori isolates from children.
  

In addition to ulcers, H. pylori infections may also be related to the development of gastritis, gastric adenocarcinoma and lymphoma.

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