Helicobacter pylori: opportunistic member of the normal microflora or agent of communicable disease?

Abstract

This is a book about the normal microflora. It concerns those bacteria that have, over the millennia, evolved to inhabit the multitude of ecological niches provided by the nooks and crannies of the human body. In certain circumstances these organisms may induce disease, especially if the balance of the microflora changes or the bacteria move into a different niche. The evolved pathogens that specifically cause major diseases such as diphtheria or tuberculosis are not our concern. Inclusion of the bacterium Helicobacter pylori is justified by the title to this chapter; there are those who still believe this bacterium is not a true pathogen, rather it is an opportunistic colonizer that inhabits already damaged gastric mucosa (Graham, 1995). As is seen below, the answer to the question is unequivocal. H. pylori is indeed a major gastroduodenal pathogen responsible for millions of deaths per year and for great discomfort to many of the world’s population. Thus, we could have deleted this chapter and claimed that it sits more properly within a text on infectious disease. However, H. pylori shares many of the characteristics of the normal microflora. This is a bacterium that has evolved over the millennia to inhabit its niche of the gastric mucosa. The hypothesis suggested in the conclusion is that in previous times H. pylori was indeed normal microflora and it is only the consequences of human development that have produced circumstances in which the bacterium is pathogenic. This is the reason that we consider that a chapter on this fascinating bacterium can greatly contribute to this treatise on the normal microflora and its medical importance.