What is Auto-Brewery Syndrome?
Auto-brewery syndrome (ABS), also known as gut fermentation syndrome or endogenous alcohol fermentation syndrome, is a rare medical condition in which the gastrointestinal tract produces excessive endogenous ethanol from ingested carbohydrates, resulting in signs and symptoms of alcohol intoxication without alcohol consumption. 1, 2, 3
Pathophysiology
- The syndrome occurs when specific microorganisms in the gastrointestinal tract ferment dietary carbohydrates into ethanol, leading to measurable blood alcohol levels and clinical intoxication 3, 4
- Causative organisms include Candida species (C. albicans, C. glabrata, C. kefyr, C. parapsilosis, C. intermedia), Saccharomyces cerevisiae, Klebsiella pneumoniae, and E. coli 3, 4
- The condition involves gut dysbiosis with overgrowth of fermenting organisms, impaired intestinal barrier function, and dysregulation of the hypothalamic-pituitary-adrenal axis 4
Clinical Presentation
Patients present with classic signs of alcohol intoxication after consuming carbohydrate-rich meals, including:
- Staggering gait and slurred speech 1
- Gastrointestinal distress 1
- Confusion and altered mental status 1
- Elevated blood or breath ethanol levels without alcohol ingestion 1, 2
High-Risk Populations
- Patients with short bowel syndrome are particularly susceptible due to altered gut anatomy and bacterial overgrowth 5
- Prior antibiotic use has been reported in several cases, suggesting disruption of normal gut flora as a predisposing factor 3
Diagnostic Approach
The confirmatory test is elevated blood or breath ethanol levels after a glucose challenge test 1, 4:
- Administer a carbohydrate load (glucose challenge)
- Measure serial blood ethanol concentrations over several hours
- Positive test shows rising ethanol levels without alcohol consumption
Obtain gastric fluid and fecal cultures to identify causative organisms 5:
- Culture for Candida species, Saccharomyces, Klebsiella, and E. coli
- Perform sensitivity testing to guide antifungal or antibiotic therapy
Management Strategy
Primary treatment consists of antifungal medications (for fungal causes) or antibiotics (for bacterial causes) combined with strict carbohydrate restriction 1, 3:
- Initiate empirical antifungal therapy (e.g., fluconazole) while awaiting culture results if fungal etiology suspected 4
- Prescribe low-carbohydrate diet to eliminate substrate for fermentation 1, 5
- Consider probiotics to restore normal gut flora 3
- Fecal microbiota transplantation may have a potential role in refractory cases 3
Critical Differential Diagnoses
Before confirming ABS, rule out:
- Covert alcohol consumption (most common alternative explanation)
- Medication-induced symptoms
- Other causes of altered mental status
- Metabolic encephalopathy
Associated Complications
Patients may develop metabolic dysfunction-associated fatty liver disease (MAFLD) and steatohepatitis from chronic endogenous ethanol production 4:
- Monitor liver function tests regularly
- Screen for hepatic steatosis with imaging if chronic symptoms
The condition carries severe psychosocial consequences 4:
- Social rejection and family separation
- Legal ramifications including DUI charges
- Employment termination
- Court-ordered alcohol rehabilitation despite no alcohol consumption
- Deteriorating mental health and suicidality from disbelief by others
Monitoring and Follow-Up
- Repeat glucose challenge testing after treatment to confirm resolution 4
- Serial stool cultures to document eradication of causative organisms 5
- Long-term dietary counseling to maintain carbohydrate restriction 1
- Screen for recurrence if symptoms return after carbohydrate reintroduction 5
Key Clinical Pitfall
The primary pitfall is failure to consider ABS in the differential diagnosis of unexplained intoxication, leading to misdiagnosis, inappropriate psychiatric referrals, legal consequences, and delayed treatment 4. The condition remains largely underdiagnosed due to lack of clinician awareness 3, 4.