A fifty-eight year old woman enters the emergency room with slurred speech, poor motor coordination, vomiting, and the smell of alcohol on her breath. Yet, she has not had anything to drink. She is admitted to the hospital to undergo testing, including blood alcohol concentration (BAC) screening after glucose administration. After 36 hours in the emergency room, her BAC is measured at 14mg/dL, below the legal driving limit of 80mg/dL. However, after receiving a colonoscopy, her BAC jumps to 315mg/dL, despite consuming no alcohol during her hospital stay. So, what exactly is happening here? If not caused by external factors, how has the patient manifested these hallmarks? The only remaining explanation: her body is producing them endogenously.

Auto-brewery Syndrome (ABS) is a rare yet serious condition in which patients present with symptoms of intoxication due to increased absorption of ethanol produced by gut microbiota. There is no universal standard for diagnosing and treating ABS, and methods typically used in diagnosis are often expensive. Many patients have to visit multiple doctors in hopes of being diagnosed, but are often dismissed as having alcohol use disorders. However, new breakthrough research may change the way ABS is diagnosed and treated.

In a recent study , Cynthia L. Hsu and her team of scientists screened 22 individuals clinically diagnosed with ABS and 21 unaffected household partners. They collected stool samples from ABS patients experiencing symptom flares and compared various biomarkers to those of household partners. After 24 hours, there were markedly higher levels of ethanol production in samples from individuals with ABS. Researchers observed that ABS patients had higher levels of Proteobacteria, specifically Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae).

Beyond having increased levels of Proteobacteria, individuals with ABS also had certain elevated microbial metabolic pathways compared to unaffected household partners. Specifically, more heterolactic and mixed-acid fermentation pathways were activated in ABS patients. Enzymes involved in ethanol production were also elevated for patients compared to household partners. Researchers primarily found increased expression of the genes associated with these pathways in E. coli and K. pneumoniae.

Hsu and her team also examined levels of stool metabolites in individuals with and without ABS. They found significantly higher levels of acetate in samples from patients with symptom flares. Acetate is a product of ethanol metabolism, and it may be converted to acetyl-CoA which may undergo ethanol fermentation. Fecal acetate levels also had a strong, positive correlation with patient BAC at the time of sample collection. This suggests acetate levels may be used as a tool in ABS diagnosis.

Currently, patients are advised to follow a low carbohydrate diet, maintain low stress levels, and abstain from drinking alcohol. They may successfully enter remission for years, but symptoms often return with seemingly no cause. In many cases, experiencing flare ups after remission and subsequent chronic alcohol exposure causes patients to present with physical problems like liver disease and mental health issues such as depression.

More work must be done to provide a long-term solution for ABS patients. Hsu’s team investigated the primary form of ABS treatment, fecal microbiota transplant (FMT). This procedure involves the transplant of stool with a healthy microbiome into the colon of a patient with ABS. They found that a more widespread antibiotic pretreatment, as well as monthly antibiotic treatments post-operation, helped prevent ABS symptoms for a longer period of time. This has provided one step in elucidating the best path for treatment. Regulating ethanol metabolism in addition to FMT may give these patients the best chance of entering remission. Future studies should investigate which genomic differences lead to alcohol tolerance in the pathogenic strains found in ABS patients, which would in turn help determine targets for novel treatments.