in human health and disease: Mechanisms for local gastric and systemic effects.

() is present in roughly 50% of the human population worldwide and infection levels reach over 70% in developing countries. The infection has classically been associated with different gastro-intestinal diseases, but also with extra gastric diseases. Despite such associations, the bacterium frequently persists in the human host without inducing disease, and it has been suggested that may also play a beneficial role in health. To understand how can produce such diverse effects in the human host, several studies have focused on understanding the local and systemic effects triggered by this bacterium. One of the main mechanisms by which is thought to damage the host is by inducing local and systemic inflammation. However, more recently, studies are beginning to focus on the effects of and its metabolism on the gastric and intestinal microbiome. The objective of this review is to discuss how has co-evolved with humans, how presence is associated with positive and negative effects in human health and how inflammation and/or changes in the microbiome are associated with the observed outcomes.