- In the previous five years, the investigators initially eliminated children taking proton pump inhibitors (PPIs) (e.g., omeprazole); Na+/H+ ATPase channel inhibitors. PPIs have a minimum inhibitory concentration (MIC) against Hp in vitro, and therefore may reduce the overall bacterial load, diminishing the ability to detect infection, and resolve gastroduodenal mucosal inflammation, confounding characterization of cellular host response to Hp infection. However, due to the pervasive use of PPIs in the pediatric population, and the exclusion of potential cases, the investigators improved their culture sensitivity techniques and are able to successfully detect the organism in the setting of a child on a PPI. This will be taken into account when characterizing the gastric mucosal inflammatory phenotype and comparative analyses are performed.