In 2011, an otherwise healthy man in the US injured his thumb so severely he required antibiotics. Doctors prescribed oral cephalexin, a common antibiotic used to treat infections.
One week after completing his course he began to experience some curious symptoms, as documented in a recent BMJ Open Gastroenterology case report. As well as memory loss, "brain fog," and episodes of depression, he started going through some personality changes and acting uncharacteristically aggressive. This went on for some years, and finaly in 2014 he was referred to a psychiatrist who treated him with antidepressants.
Then one morning, he was pulled over by police on suspicion of driving under the influence of alcohol. He refused a breathalyzer but was hospitalized, where his blood-alcohol level was found to be 200 mg/dL, equivalent to about 7-10 drinks (depending on your weight) and enough to cause nausea, vomiting, impaired understanding and sensations, memory blackout, and even loss of consciousness.
But, as the patient insisted to the skeptical doctors and police officers, he hadn't touched a drink at all.
Following the incident, his aunt bought him a breathalyzer to record the levels of alcohol on his breath. She had heard of similar cases of people getting drunk without actually drinking any alcohol, and thought he should track his measurements. She also prompted him to go visit a physician in Ohio who had successfully treated someone with the condition.
Sure enough, after a carbohydrate test – where the patient is given a carbohydrate meal and has their blood-alcohol levels monitored over a few hours – showed elevated levels despite consuming no alcohol his doctors found Saccharomyces cerevisiae (brewer’s yeast) in his stool and diagnosed him with the extremely rare auto-brewery syndrome (ABS).
Also known as gut fermentation syndrome, ABS causes the digestive system to produce enough ethanol to get you intoxicated. All people's guts produce a small amount of alcohol whilst digesting sugary and starchy food, but when Saccharomyces cerevisiae is present in your gut it's on a whole other level. Several cases have been reported in recent years, usually involving baffled patients being arrested for drink driving after drinking nothing and eating something like bread or basmati rice.
The patient was given antifungal medications to treat the condition, but was soon back in hospital after it flared up again and he had a fall and hit his head, causing intracranial bleeding. Here, his doctors wouldn't believe he hadn't been drinking after his blood-alcohol levels ranged from 50 to 400 mg/dL.
After searching for help, the now 46-year-old man came across the doctors from Richmond University Medical Center in New York City, who would eventually document this first-of-its-kind case.
Give or take a few bumps in the road – he was taken off carbs and treated again with oral antifungal medication, then, unbeknownst to the doctors, he ate pizza and drank sugary soda, causing a "severe" relapse of ABS (before you judge, who among you can honestly say they'd refuse pizza?) – he was diagnosed with ABS, in what is the first documented case of the syndrome resulting from antibiotics.
"We postulate that the antibiotic altered his gut microbiome, allowing fungal growth," they wrote in the case report. "This diagnosis should be considered in any patient with positive manifestations of alcohol toxicity who denies alcohol ingestion."
The report confirms 1.5 years later, he remains symptomless and sober, his gut no-longer a micro-brewery.