Recurrent infection of the gastrointestinal tract Helicobacter pylori infection A recurrent infection of the GI tract with helicobacter pylori, a gram-negative, microaerophilic bacterium usually found in the stomach. UMLS:C0850666 HP:0005202 The bacterial pathogen Helicobacter pylori has co-evolved with humans and colonizes approximately half of the human population, but only causes overt gastric disease in a subset of infected hosts.