Pathogens Surviving the Stomach

This week's #micromeded is all about one of the GI tract's first defenses against pathogens. Because of the low pH, most pathogens cannot survive in the stomach. In this figure, I depict two ways pathogens evade this host defense.

The first mechanism in this chart is H. pyroli which, through the production of urease, splits urea into NH4+ and CO2. This creates a locally tolerable environment for the bacteria. This is how the bacterium is able to survive and cause disease!

The presence of H. pylori can be tested with the urea breath test (UBT). After ingestion of radiolabeled urea, the presence of labeled CO2 on expiration is a surrogate marker for the presence of H. pyroli in the stomach.

The second mechanism here is an exogenous one. After being prescribed a PPI like omeprazole, the pH of the stomach rises slightly to protect the esophagus from damage. This, however, allows pathogens like Vibro spp. to pass through the stomach more easily.

Figure created with Biorender.com