Is H. pylori a normal flora of the stomach?

Question

or it is pathogenic bacteria?

Answer 1

There is not really any normal flora of the stomach, though a little over half the world's population has H pylori in the stomach. This does not mean that they all have ulcers, though. The immune system will attempt to defeat the infection, but it is usually unable to reach the H pylori due to its odd location. It is possible that some of what causes an ulcer is not the bacteria itself but the body's inflammatory response.