ScienceDaily (Nov. 29, 2008)

"Halitosis is a common problem in humans, and bad breath is largely caused by periodonitis, tongue debris, poor oral hygiene and badly fitted fillings," said Dr. Suzuki. "Bacteria produce volatile compounds that smell unpleasant, including hydrogen sulphide, methyl mercaptan and dimethyl sulphide. Doctors often measure the levels of these compounds to diagnose the problem. Gastrointestinal diseases are also generally believed to cause halitosis."

Patients who were carrying H. pylori had more blood in their saliva and were also carrying Prevotella intermedia, which is one of the major periodontal bacteria.

"Although the presence of H. pylori in the mouth does not directly cause bad breath, it is associated with periodontal disease, which does cause bad breath," said Dr. Suzuki.

http://www.sciencedaily.com/releases/2008/11/081123222846.htm