Microbes are in the news again. I recently read one of the Medical Mysteries occasionally featured in the Washington Postabout a man who kept becoming disoriented, with sometimes "trance-like" behavior, for no obvious reason. As related in the article "For years he'd been found in a stupor, until a fall led to a surprising diagnosis," by David Wahlberg, the man's wife believed he was developing dementia, as there was no other obvious cause for his symptoms.
Eventually, though, it was discovered that when the man had these episodes, he had very high blood alcohol content (0.363; 4+ times the legal limit). But it wasn't because he was drinking alcohol. The blame for this turned out to be his gut microbes. He has "auto-brewery syndrome," where yeast and bacteria in the gut ferment carbohydrates in such a way that produces alcohol. This causes a paradoxical alcoholic intoxication of someone who did not consume alcohol.
The man was discovered to have a substantial overgrowth of Saccharomyces cerevisiae, also known as "brewer's yeast." He was treated with anti-fungal medication, but it was not reliably effective and he kept having episodes. It turns out that gut bacteria also contribute to auto-brewery syndrome, so eventually he had a series of fecal transplants that were finally able to give him relief from the intoxication.