Helicobacter pylori: pathogen and symbiont.

There are puzzles in defining the exact role of Helicobacter pylori infection in humans. The bacterium, which is associated with human disease of the upper gastrointestinal tract, may otherwise exist as a commensal with probable symbiotic association in some human hosts. Although virulence associated genes have been detected in some strains which explain their pathogenicity, their pathogenic effect and subsequent clinical manifestations seem to vary in different human populations or geographical locations. Some human hosts remain predominantly asymptomatic in spite of the "virulent" H. pylori strain(s) they harbour. There are probable benefits of H. pylori colonisation of the human gastric mucosa. Thus the recommendation of eradication therapy in patients with known peptic ulcer disease may be more advantageous than the "test and treat policy", which suggests treatment of uninvestigated dyspeptic patients, who may not have any lesions.