In a strange medical case, a 27-year-old man in China was found suffering from a form of liver inflammation known as nonalcoholic steatohepatitis and had a weird history of becoming drunk without really drinking.
A high blood alcohol reading of about 400 milligrams per decilitre results from at least a dozen shots of hard liquor but the subject of this case study could record the high reading after just a good supply of fruit juice and a few plates of carbs. It is actually possible for our gut microflora to ferment carbohydrates in our food into an intoxicating level of ethanol.
This extremely rare condition is called the auto-brewery syndrome (ABS), and this patient’s case could provide insight into liver damage that ensues while intestinal bacteria turn carbohydrates into their very own homebrew.
With just a handful of cases studied in detail, this uncommon syndrome is apparently caused by an overrepresentation of the brewer’s preferred fungal companion, Saccharomyces cerevisiae. This time, the researchers decided to look a little further for the microbe responsible the non-drinker’s states of intoxication and resulting liver disease.
Paediatrician Jing Yuan from Capital Institute of Paediatrics in Beijing, says, “We initially thought it was because of the yeast, but the test result for this patient was negative. Anti-yeast medicine also didn’t work, so we suspected [his disease] might be caused by something else.”
A search through the patient’s faeces managed to categorize a potential candidate in the form of a microbe called Klebsiella pneumoniae. The researchers compared his isolated microbes with those found in 43 other patients with non-alcoholic fatty liver disease (NAFLD), and an additional 48 healthy individuals. During the study, they determined that the abundance of K. pneumoniae increased by around 0.02 percent in most individuals but in their subject, the change was closer to a huge 19 percent.
With the causal agent in sight, the team successfully isolated strains of the bacterium that were tolerant of alcohol and could generate significant amounts of it with and without oxygen.
Revealingly, the abundance of these two fermenting strains and their ability to roil out alcohol were higher in those with NAFLD than in healthy volunteers. In reality, 60 percent of the NAFLD patients were detected with strains of the bacterium that could generate medium to high amounts of alcohol, compared with just 6 percent presence in the healthy group.
In order to verify a link between the K. pneumoniae and fatty liver disease, the researchers infected the guts of test mice with the bacterium. Just two months later, their livers showed serious signs of scarring.
Although, K. pneumoniae may still not be the primary cause of all cases of liver disease that don’t have clear links to alcohol consumption but it provides a good starting place for those concerned.
Yuan says, “NAFLD is a heterogeneous disease and may have many causes. Our study shows K. pneumoniae is very likely to be one of them. These bacteria damage your liver just like alcohol, except you don’t have a choice.”
The mechanism of how and why this bacterial strain sets up a microbrewery in some hosts and not in others isn’t clear. But the team whose research was published in Cell Metabolism plans on further investigating the microbe’s role in liver disease.
Fellow researcher Di Liu from the Chinese Academy of Sciences, says, “Having these bacteria in your gut means your body is exposed to alcohol constantly. So does being a carrier mean you would have higher alcohol tolerance? I’m genuinely curious!”