Helicobacter pylori becomes resistant to stomach acid once it safely embeds itself in the mucous membrane. It uses its urease enzyme to break down urea in the stomach acid into bicarbonate and ammonia, neutralizing the acid around it.
By creating a zone of acid-neutralizing chemicals, H. pylori protects itself from the stomach acid's attack. Due to this acid-neutralizing effect, breath tests are used to detect infection. The bacteria's self-protective mechanism demonstrates that eradicating bacteria residing in the stomach lining is impossible for our body's defense system. When infected with H. pylori, our immune system responds by releasing white blood cells, killer T cells, and other infection-fighting substances, but these defenses fail to penetrate the stomach lining and cure the infection.