Non-absorbable antibiotics worsen alcohol-associated liver disease in gastric acid-suppressed mice

Gastric acid-suppressive medications, particularly proton pump inhibitors (PPIs), are commonly used in patients with alcohol-associated liver disease (ALD) to prevent and manage upper gastrointestinal bleeding, gastroesophageal reflux disease, and non-steroidal anti-inflammatory/aspirin-induced gastroesophageal damage. By inhibiting the gastric H⁺/K⁺-ATPase, PPIs suppress acid secretion and impair bacterial killing, thereby promoting gut dysbiosis that disrupts barrier integrity and enhances bacterial translocation, ultimately exacerbating liver injury. PPIs are frequently co-administered with antibiotics for indications such as gastrointestinal bleeding, Spontaneous Bacterial Peritonitis (SBP), other infections, or hepatic encephalopathy prophylaxis, but the consequences of this combined therapy on gut microbial ecology and disease outcomes remain unclear. Our study addresses this gap by showing how PPI use, alone or with antibiotics, reshapes the gut microbiome and aggravates liver disease progression. In previous studies, we showed that PPIs promote dysbiosis and ALD progression in mice and humans by facilitating intestinal expansion and hepatic translocation of Gram-positive Enterococcus. Fecal cytolysin, an Enterococcus faecalis exotoxin that induces hepatocyte death, predicts mortality in patients with alcohol-associated hepatitis (AH). In this study, we have examined the mechanism by which PPIs alone and in combination with non-absorbable antibiotics targeting Gram-positive bacteria influence ALD, as well as the disease mechanisms associated with cytolytic Enterococcus faecalis and the development of therapeutic strategies. In mice, alcohol administration during gastric acid suppression promoted expansion of Gram-positive taxa, including cytolysin-producing Enterococcus. Similarly, PPI use in patients with AH was associated with increased fecal Enterococcus and higher 30-d mortality, underscoring the translational relevance of our findings. Unexpectedly, treatment of acid-suppressed mice with non-absorbable antibiotics designed to suppress Gram-positive bacteria worsened ethanol-induced steatohepatitis: while Enterococcus abundance decreased, Streptococcus and other potentially pathogenic taxa expanded, leading to increased bacterial translocation and aggravated liver injury. In patients with cirrhosis or metabolic dysfunction-associated steatotic liver disease (MASLD), PPIs did not promote Enterococcus expansion, indicating etiology-dependent microbiome responses. Finally, we identified dipalmitoylphosphatidylcholine and Caspase-1 inhibitor as in vitro and in vivo modulators of cytolysin activity, highlighting potential therapeutic avenues. Collectively, our study demonstrates how PPIs and non-absorbable antibiotics targeting Gram-positive bacteria interact with the gut microbiome to drive ALD, underscoring the need for careful therapeutic management.