Causes of failure of eradication of Helicobacter pylori

Is the environment of the mouth necessarily different to
the stomach? Is the environment of the mouth
necessarily different to the stomach in people infected
with H Pylori infection?

Could it not be that people discovered to have H Pylori
are already receiving acid suppression therapy? Could
bile presence in the stomach predispose to H Pylori
infection. Alternatively, in Gastro-Oesophageal Reflux
Disease (GORD), it is emerging that susceptibility is
conferred by derrangement of defence mechanisms
such as those provided by EGF which may act on the
Oesophageal epithelium and carbonic anhydrase (CA).
CA is present in secretory cells of the salivary gland
and helps bring about the high pH of saliva. In addition,
isoforms of CA may be secreted themselves be
secreted in saliva. It may be that people are
susceptible to H Pylori because of a reduced or absent
CA.

Alternatively, it may be the other way round. H Pylori
may prefer a genuinely normal stomach pH. In which
case, is it possible that such acidic environments are
not produced in the mouth as a function of the
consumption of sugary foods?