Clinical Report: Antibiotic precedes auto-brewery relapse

Overview

A man in his mid-40s with known auto-brewery syndrome (ABS) developed severe endogenous ethanol intoxication five days after starting amoxicillin/clavulanate for community-acquired pneumonia, following approximately two years without symptoms. He recovered within hours with supportive care after the antibiotic was discontinued. The case authors considered antibiotic-associated microbiome disruption a possible contributor but emphasized that a single case cannot establish causation.

Background

ABS is characterized by endogenous ethanol production associated with gastrointestinal microorganisms and can present as apparent alcohol intoxication despite reported abstinence. The patient’s earlier evaluation identified small intestinal bacterial overgrowth and increased Proteobacteria, predominantly Enterobacter species; a 14-day course of rifaximin and probiotics was followed by an approximately two-year asymptomatic period. The authors noted that ABS has been associated with ethanol-producing yeasts, while bacteria may also contribute to ethanol production. They cited prior case reports in which antibiotic exposure preceded symptoms in 7 of 16 cases, but the evidence does not establish a causal relationship.

Data Highlights

Key Findings

• The patient was found unresponsive five days after beginning amoxicillin/clavulanate and had a Glasgow Coma Scale score of 9 and blood alcohol concentration of 43.6 mmol/L despite reported abstinence, confirmed by his partner.
• Arterial blood gas results were within normal limits, cranial computed tomography showed no intracranial hemorrhage or structural brain damage, and empiric naloxone and flumazenil produced no clinical improvement.
• Amoxicillin/clavulanate was discontinued; after rehydration and supportive intensive care, the patient recovered within hours and was discharged without neurologic deficits.
• Earlier evaluation in 2023 identified small intestinal bacterial overgrowth and increased Proteobacteria, predominantly Enterobacter species. Rifaximin and probiotics were followed by approximately two years without ABS symptoms.
• The investigators proposed that antibiotic-associated dysbiosis may have contributed to recurrence, while noting that the temporal association in this single-patient report cannot establish that amoxicillin/clavulanate caused it.
• The authors cited prior case reports in which antibiotic exposure preceded symptoms in 7 of 16 ABS cases and stated that ABS should be considered in otherwise unexplained intoxication when reported abstinence is credible; they advised caution with antibiotic therapy in patients with known ABS.

Clinical Implications

The authors state that ABS should be considered when alcohol intoxication is otherwise unexplained and reported abstinence is credible. For patients with known ABS, they advise approaching antibiotic therapy with caution, while recognizing that this case does not establish antibiotic causation and that the patient’s prior alcohol overuse and gastrointestinal findings complicate interpretation.

Conclusion

This case describes ABS recurrence after recent amoxicillin/clavulanate exposure following a prolonged symptom-free interval. Antibiotic-associated dysbiosis is a proposed explanation, not a demonstrated cause.

Related Resources & Content

1. Widmer et al., Oxford Medical Case Reports, 2026 — Co-amoxicillin–induced reactivation of auto-brewery syndrome in a patient treated for community acquired pneumonia: a clinical case report
2. StatPearls, NCBI Bookshelf, year not specified — Auto-Brewery Syndrome
3. Nature Microbiology, 2026 — Gut microbial ethanol metabolism contributes to auto-brewery syndrome in an observational cohort
4. the medicine maker — Treating Before Infection?
5. the medicine maker — Antibiotic Apocalypse: Part II
6. the medicine maker — Down with the Resistance
7. ASCO Publications — Antibiotic cycling to decrease bacterial antibiotic resistance: A 7-year experience on a bone marrow transplant unit
8. Co-amoxicillin–induced reactivation of auto-brewery syndrome in a patient treated for community acquired pneumonia: a clinical case report
9. Auto-Brewery Syndrome - StatPearls
10. Gut microbial ethanol metabolism contributes to auto-brewery syndrome in an observational cohort
11. Auto-Brewery Syndrome - StatPearls - NCBI Bookshelf
12. Gut microbial ethanol metabolism contributes to auto-brewery syndrome in an observational cohort | Nature Microbiology
13. Co-amoxicillin–induced reactivation of auto-brewery syndrome in a patient treated for community acquired pneumonia: a clinical case report | Oxford Medical Case Reports | Oxford Academic
14. Auto-brewery Syndrome Presenting with Recurrent Episodes of Reduced Level of Consciousness, Confusion, and Ataxia (P12-5.030) | Neurology
15. Auto-Brewery Syndrome: Symptoms, Causes & Treatment