What are the causes of auto‑brewery syndrome?

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Auto-Brewery Syndrome: Causes and Pathophysiology

Auto-brewery syndrome (ABS) is caused by overgrowth of fermenting microorganisms—primarily yeasts (Candida and Saccharomyces species) and certain bacteria (particularly Klebsiella pneumoniae)—in the gastrointestinal tract or oral cavity that convert ingested carbohydrates into endogenous ethanol. 1, 2

Primary Causative Microorganisms

Fungal Pathogens

  • Candida species are the most commonly implicated fungi, including C. albicans, C. glabrata, C. intermedia, C. parapsilosis, and C. kefyr 1
  • Saccharomyces cerevisiae (brewer's yeast) has been identified as a causative organism in multiple case reports 1
  • These yeasts ferment dietary carbohydrates into alcohol through their metabolic processes 3

Bacterial Pathogens

  • Klebsiella pneumoniae is the primary bacterial species identified in ABS cases 1
  • Periodontal disease bacteria in the oral cavity can produce alcohol in combination with oral Candida species 4
  • Recent research in Nonalcoholic Fatty Liver Disease suggests bacterial origins of endogenous alcohol production may represent additional causal organisms not yet fully characterized in ABS 1

Predisposing Factors and Risk Conditions

Prior Antibiotic Exposure

  • Previous antibiotic treatment is a common predisposing factor, as antibiotics disrupt normal gut microbiota and allow overgrowth of fermenting organisms 1
  • This disruption creates an ecological niche for opportunistic yeasts and bacteria to colonize 2

Gastrointestinal Conditions

  • Esophageal candidiasis and other fungal infections of the GI tract create environments conducive to alcohol fermentation 4
  • Structural or functional GI abnormalities may promote microbial overgrowth 3

Oral Cavity Pathology

  • Significant tooth decay and periodontal disease provide sites for Candida colonization and bacterial overgrowth that can produce alcohol in the oral cavity 4
  • High levels of C. albicans in the oral cavity combined with periodontal bacteria create a fermentation environment 4

Impaired Alcohol Metabolism

  • Poor alcohol-degrading enzyme function prevents adequate clearance of endogenously produced ethanol, allowing accumulation to intoxicating levels 4
  • This metabolic deficiency amplifies the clinical impact of even modest endogenous alcohol production 4

Dietary Factors

  • High carbohydrate intake provides substrate for microbial fermentation into alcohol 2, 3
  • The syndrome manifests when fermenting organisms convert consumed carbohydrates to ethanol 1

Pathophysiological Mechanism

The fundamental process involves microbial colonization of the GI tract or oral cavity with organisms possessing fermentative capacity 1. When patients consume carbohydrate-rich foods, these microorganisms metabolize the carbohydrates through fermentation pathways, producing ethanol as an end product 2, 3. The endogenously produced alcohol is then absorbed into the bloodstream, resulting in elevated blood alcohol levels and clinical intoxication despite no exogenous alcohol consumption 3.

Important Clinical Caveats

  • ABS is rare and significantly underdiagnosed in clinical practice, requiring high clinical suspicion 1, 2
  • The condition can occur in healthy individuals when the right combination of microbial overgrowth and substrate availability exists 4
  • Multiple organism types may coexist and contribute to alcohol production simultaneously, as demonstrated in cases with both oral fungi and periodontal bacteria 4
  • The syndrome has serious social and legal consequences when patients present with intoxication symptoms, including potential DUI charges, despite not consuming alcohol 1, 2

References

1
Research

Gut fermentation syndrome: A systematic review of case reports.

United European gastroenterology journal, 2021

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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