According to a study published in the Journal of Medical Microbiology, the Helicobacter pylori, or H. pylori, bacteria can indeed cause bad breath. Known as the bacterium that causes stomach ulcers and cancer, H. pylori is now thought to cause bad breath and gum disease when it occurs in the mouth.
H. pylori is a spiral-shaped bacterium found in the stomach. Studies show that it is responsible for roughly 80 percent of stomach ulcers and 90 percent of ulcers occurring in the upper end of the small intestine, or duodenum. It can also cause gastritis (stomach inflammation) and spur the production of excess stomach acid. With time, an H. pylori infection can even lead to an increased risk of stomach cancer, WebMD notes.
When the H. pylori bacterium takes root in the mouth, it can point to periodontal disease, which in turn leads to chronic bad breath—known as halitosis. Results of a Japanese study found H. pylori in the mouths of 21 out of 326 participants with halitosis, or 6.4 percent. The concentration of bad breath gas and the level of oral disease was considerably higher in these participants than in those without the bacterium, Science Daily reports.
According to U.S. News, H. pylori is just one potential cause of bad breath. Other common culprits include poor oral hygiene, medications that cause dry mouth, diet, skipping breakfast, mouth breathing, heavy alcohol consumption, respiratory tract infections and ongoing illness.